Advances and challenges in gastric cancer testing: the role of biomarkers

HER2

HER2 is a member of the epidermal progress issue receptor (EGFR) household of receptor tyrosine kinases (RTKs) and is encoded by ERBB2 on chromosome 17^12,22. HER2 prompts downstream pathways via heterodimerization and tyrosine phosphorylation-mediated sign transduction²³. Main signaling pathways activated by HER2 embrace the rat sarcoma/quickly accelerated fibrosarcoma/mitogen-activated protein kinase kinase/extracellular signaling associated kinase (RAS/RAF/MEK/ERK) and phosphoinositide 3-kinase/protein kinase B/mammalian goal of rapamycin (PI3K/AKT/mTOR) pathways, which regulate cell proliferation, differentiation, and survival and take part within the tumorigenesis of many varieties of most cancers, together with breast, gastric, and colorectal cancers (Figure 2)²³. HER2 is overexpressed and/or amplified in roughly 20% of sufferers with gastric most cancers²² and HER2-positive tumors are sometimes extra aggressive and extra prone to recur⁸. The prognostic significance of HER2 expression in gastric most cancers, in contrast to breast most cancers, has not been established¹⁶. Some research have advised that HER2-positivity is related to a poorer prognosis in gastric most cancers sufferers²⁴. As early as 2000, Allgayer et al.²⁵ reported that rising HER2 expression is related to shorter disease-free (P = 0.023) and general survival (OS) (P = 0.0160) in a consecutive potential collection of 203 gastric most cancers sufferers. Allgayer et al.²⁵ additionally confirmed that HER2 is an unbiased prognostic issue for OS amongst sufferers who obtained healing resection [risk ratio (RR) = 1.54, 95% confidence interval (CI): 1.08–1.67, P = 0.049] and amongst all sufferers (RR = 1.33, 95% CI: 1.28–1.38, P = 0.028). Nonetheless, there are additionally research which have proven HER2 just isn’t an unbiased prognostic issue of affected person consequence, besides in a really small subset of sufferers with intestinal histology^26–28.

Determine 2

Key molecular alterations and signaling pathways concerned within the pathogenesis and development of gastric most cancers, together with chosen focused therapies (tailored from Lei et al.⁸). Many biomarkers have been related to gastric most cancers, similar to molecules in progress elements pathways and immune checkpoint management modulators. Development issue receptors (e.g., HER2, MET, and FGFR2) sometimes activate important downstream pathways via dimerization and tyrosine kinase signaling. The downstream pathways, together with PI3K/AKT/mTOR, RAS/RAF/MEK/ERK, and JAK/STAT/IRF, mediate important mobile processes, together with progress, proliferation, differentiation and survival, and take part within the tumorigenesis and development of many most cancers sorts. DKK1 regulates the Wnt/β-catenin signaling pathway, which can be a necessary pathway concerned in cell proliferation, migration, and loss of life. PD-L1 binds to PD-1 and suppresses T-cell receptor signaling, and this mechanism is often hijacked by most cancers cells to flee immune recognition. On a associated be aware, dysregulated expression of the MMR genes can impair mobile restore perform throughout DNA replication, ensuing within the MSI-H/dMMR phenotype. This phenotype contributes to gastric most cancers via completely different mechanisms, together with an upregulated PD-L1 expression. Likewise, EBV is related to completely different oncogenic results and it’s identified to extend PD-L1 expression via the JAK/STAT/IRF pathway. B7-H3 and VISTA are additionally immune checkpoint proteins and have been related to immune invasion in gastric most cancers. One other notable biomarker is CLDN18.2, a decent junction protein generally expressed in differentiated gastric mucosa cells. CLDN18.2 might develop into extra uncovered when tight junctions are disrupted upon malignant transformation of gastric epithelial cells. By way of biomarker-guided remedies for gastric most cancers, trastuzumab and trastuzumab deruxtecan are beneficial for sufferers with HER2-positivity. PD-L1-positivity and MSI-H/dMMR can information using immunotherapies, similar to pembrolizumab. Zolbetuximab has been permitted for sufferers with CLDN18.2-positive illness in some nations. Extra focused therapies, together with savolitinib for MET-positive sufferers, are at present beneath medical investigation. AKT, protein kinase B; APC, adenomatous polyposis coli; CLDN18.2, claudin 18.2; CKIα, casein kinase Iα; DKN-01, Dikkopf-1 monoclonal antibody 1; DKK1, Dikkopf-1; DVL, matted; EBV, Epstein-Bar virus; EBNA, Epstein-Bar nuclear antigen; ERK1/2, extracellular signal-regulated kinase 1/2; FGFR2, fibroblast progress issue receptor 2; HER2, human epidermal progress issue receptor 2; GSK-3β, glycogen synthase kinase 3β; IFH, interferon; IRF, interferon regulatory issue; JAK, Janus kinase; LRP5/6, low-density lipoprotein receptor-related protein 5/6; MEK1/2, mitogen-activated protein kinase 1/2; MSI-H/dMMR, microsatellite instability excessive/faulty mismatch restore; mTOR, mammalian goal of rapamycin; PD-1, programmed death-1; PD-L1, programmed death-ligand 1; PDK1, phosphoinositide-dependent protein kinase 1; PI3K, phosphoinositide 3-kinase; PIP2, phosphatidylinositol diphosphate; PIP3, phosphatidylinositol 3-phosphate; PTEN, phosphatase and tensin homolog; RAF, quickly accelerated fibrosarcoma; RAS, rat sarcoma; STAT, signaling transducer and activator of transcription; TCF/LEF T-cell issue/lymphoid enhancer issue; TSC1/2, tuberous sclerosis advanced 1/2; VISTA, V-domain immunoglobulin-containing suppressor of T-cell activation.

IHC and in situ hybridisation (ISH) are at present beneficial to detect HER2 overexpression/amplification^6,12. The US Nationwide Complete Most cancers Community (NCCN) tips for gastric most cancers advocate HER2 testing for all gastric most cancers sufferers on the time of analysis if metastatic illness is documented or advised¹⁶. An IHC rating of three+ (robust full, basolateral, or lateral membranous reactivity in ≥ 10% of most cancers cells) is constructive for HER2 overexpression¹⁶. For sufferers with an IHC rating of two+ (thought-about equivocal), ISH ought to be carried out and sufferers with an HER2/centromere enumerator probe 17 (CEP17) ≥ 2 or a median HER2 copy quantity ≥ 6.0 alerts/cell are thought-about constructive¹⁶. These definitions are broadly adopted in actual world medical follow^29,30.

As early as 2010 the randomized part III ToGA trial demonstrated the efficacy of trastuzumab in HER2-postive superior gastric/gastric-oesophageal junction (GEJ) most cancers sufferers, with the trastuzumab plus chemotherapy arm displaying an extended median OS than the chemotherapy solely arm [13.8 months vs. 11.1 months, hazard ratio (HR) = 0.74, 95% CI: 0.60–0.91, P = 0.0046]³¹. Table 1 is a abstract of vital medical trials for key molecular biomarkers with revealed outcomes. This mixture remedy is now the usual first-line remedy for sufferers with HER2-positive gastric/GEJ most cancers^16,39. The part II DESTINY-Gastric 01 trial explored using trastuzumab deruxtecan, an antibody drug conjugate, in HER2-positive gastric sufferers in whom illness progressed after two strains of earlier remedy (together with trastuzumab) and demonstrated vital enchancment in tumor response and OS in comparison with the doctor’s alternative of chemotherapy²⁹. DESTINY-Gastric 02, a single-arm part II examine, additional confirmed the efficacy and security of trastuzumab deruxtecan in sufferers with illness development on or after first-line remedy with a trastuzumab-containing routine³². The usage of different anti-HER2 therapies, similar to pertuzumab and margetuximab, have additionally been studied^23,40,41. Zanidatamab, a novel bispecific anti-HER antibody, is at present being investigated in an open-label, active-comparator, part III examine (HERIZON-GEA-01)⁴².

PD-L1

PD-L1 is the second predictive biomarker for use for gastric most cancers⁴³. PD-L1 is encoded by CD274 on chromosome 9 and is the ligand of programmed death-1 (PD-1), an inhibitor checkpoint receptor expressed on cytotoxic T-cells and different immune cells^12,44,45. Binding of PD-L1 to PD-1 suppresses T-cell receptor signaling. Importantly, this signaling pathway is often hijacked by most cancers cells to flee immune surveillance (Figure 2)^12,46,47. Elevated expression of PD-L1 has been reported in as much as 65% of gastric/GEJ cancers and is related to subtypes of tumors with excessive mutational burden⁴⁸. A meta-analysis of 10 research involving a complete of 1,901 sufferers confirmed that PD-L1 expression is considerably related to bigger tumor sizes [odds ratio (OR) = 1.87, 95% CI 1.25–2.78, P = 0.002], a better probability of lymph node metastasis (OR = 2.17, 95% CI 1.04–4.52, P = 0.04), and shorter OS (HR = 1.64, 95% CI 1.11–2.43, P = 0.01)⁴⁹.

PD-L1 is expressed extra usually on immune cells within the tumor microenvironment than the tumor cells^12,50. As such, PD-L1 expression in gastric most cancers is assessed utilizing IHC and indicated utilizing the mixed constructive rating (CPS), which is calculated because the variety of PD-L1-staining cells (i.e., tumor cells, lymphocytes, and macrophages) divided by the overall variety of viable tumor cells, then multiplied by 100^16,51. A specimen is taken into account PD-L1-positive if the specimen has a CPS ≥ 1¹⁶.

At the moment, nivolumab and pembrolizumab (PD-1 inhibitors) have been broadly beneficial for superior gastric most cancers sufferers who’re PD-L1-positive^16,52,53. Different PD-L1-guided immune checkpoint inhibitors (ICIs) have additionally been permitted for gastric most cancers in some areas of the world, similar to sintilimab and tislelizumab in China⁵³. The pivotal part III CheckMate 649 trial demonstrated that nivolumab plus chemotherapy considerably improved the OS (HR = 0.71, 95% CI 0.59–0.86, P P 33. The usage of pembrolizumab in PD-L1-positive gastric most cancers sufferers has been studied in a number of vital medical trials, similar to KEYNOTE-059 (part II, later-line), KEYNOTE-061 (part III, later-line), and KEYNOTE-062 (part III, first-line), which yielded combined outcomes^54–56. A subsequent built-in evaluation of those three research demonstrated constant enhancements towards extra beneficial medical outcomes with pembrolizumab throughout strains of remedy in sufferers with a PD-L1 CPS ≥ 10⁵⁷. The part III KEYNOTE-811 trial investigated the addition of pembrolizumab to first-line trastuzumab plus chemotherapy for sufferers with HER2-positive, domestically superior or recurrent gastric most cancers. The addition of pembrolizumab considerably improved the median PFS in sufferers with a PD-L1 CPS ≥ 1 in comparison with placebo (10.8 months vs. 7.2 months, HR = 0.70, 95% CI: 0.58–0.85) however not for sufferers with a PD-L1 CPS vs. 9.6 months, HR = 1.17, 95% CI: 0.73–1.89)⁵⁸. Extra not too long ago, the double-blind, placebo-controlled, randomized part III KEYNOTE-859 trial confirmed that the median OS was longer within the pembrolizumab group than the placebo group amongst sufferers with a PD-L1 CPS ≥ 1 (13.0 months vs. 11.4 months, P vs. 11.8 months, P 34.

Microsatellite instability (MSI)/mismatch restore (MMR)

Mounting proof means that along with PD-L1 expression, response to ICIs may additionally be predicted by different biomarkers, together with MSI-high (MSI-H) or faulty MMR (dMMR)¹². In roughly 10% of gastric and GEJ most cancers sufferers, dysregulated expression of MMR genes disrupts mobile restore perform throughout DNA replication, resulting in the MSI-H/dMMR phenotype (Figure 2)⁴⁷. Testing for MSI-H/dMMR may be based mostly on polymerase chain response (PCR) or NGS for MSI, or IHC for MMR¹⁶. In response to the 2024 NCCN tips for gastric most cancers, sufferers in whom ≥ 30% of the MSI markers exhibit instability or ≥ 2 of the 5 Nationwide Most cancers Institute (NCI) or mononucleotide markers exhibiting instability are thought-about to be MSI-H¹⁶. Sufferers with lack of nuclear expression of ≥ 1 MMR proteins are thought-about to be dMMR¹⁶.

A number of research have demonstrated that MSI-H/dMMR standing can be utilized as a marker to information using ICIs for superior gastric most cancers sufferers. For instance, a put up hoc evaluation of information from KEYNOTE-059, KEYNOTE-061, and KEYNOTE-062 demonstrated that pembrolizumab or pembrolizumab plus chemotherapy conferred sturdy antitumor exercise in comparison with chemotherapy alone in sufferers with MSI-H tumors⁵⁹. A meta-analysis that included 2,545 superior gastric most cancers sufferers from KEYNOTE-061, KETNOTE062, CheckMate-649, and JAVELIN Gastric 100 (avelumab vs. chemotherapy as upkeep remedy) confirmed that close to chemotherapy, the HR for OS profit with anti-PD-1 remedy was 0.34 (95% CI: 0.21–0.54) for sufferers with MSI-H tumors and 0.85 (95% CI: 0.71–1.00) for sufferers with microsatellite steady tumors⁶⁰. Importantly, based mostly on information from 149 sufferers with MSI-H tumors throughout a number of medical trials, the U.S. Meals & Drug Administration (FDA) granted an accelerated approval for pembrolizumab in 2017 to deal with sufferers with superior MSI-H tumors, no matter tumor web site or histologic options⁶¹. This discovering marked the primary approval of a tissue/site-agnostic, biomarker-guided remedy⁶¹. At the moment, pembrolizumab, nivolumab plus ipilimumab, and dostarlimab-gxly have been beneficial by the NCCN tips for unresectable domestically superior, recurrent, or metastatic gastric most cancers sufferers with MSI-H/dMMR tumors, unbiased of PD-L1 standing¹⁶.

CLDN18.2

The claudin household of proteins are vital parts of tight junctions⁶². CLDN18.2 is encoded by the CLDN18 gene positioned at chromosome 3q22⁶². Beneath regular physiologic situations, CLDN18.2 is sort of solely expressed in differentiated gastric mucosal membrane epithelial cells, though CLDN18.2 may additionally be expressed in gastric, lung, oesophageal, and pancreatic tumor cells^62,63. In regular tissues, CLDN18.2 regulates permeability to the Na⁺ and H⁺ in gastric acid by sustaining the barrier perform of the gastric mucosa (Figure 2)^62,63. Importantly, CLDN18.2 is retained and turns into extra uncovered when tight junctions are disrupted upon malignant transformation of gastric epithelial tissue, such CLDN18.2 can function a possible goal for antibodies and different focused therapies^12,63. The position of CLDN18.2 in gastric most cancers growth and development stays elusive, with each downregulation and overexpression being reported in various proportions of sufferers throughout research⁶⁴. For instance, Sanada et al.⁶⁵ reported that downregulation of CLDN18.2 was noticed in 57.5% of gastric most cancers and correlated with poorer survival in superior gastric most cancers. Different research have reported overexpression of CLDN18.2 in gastric most cancers, starting from 29.4%–87% of sufferers⁶³. CLDN18.2 expression could also be related to a number of elements, together with most cancers stage and subtype^63,64.

The one permitted compendium diagnostic assay for CLDN18.2 IHC is the VENTANA CLDN18 (43-14A; Ventana Medical Techniques, Inc./Roche Diagnostics, Oro Valley, Arizona, USA), though different IHC strategies have additionally been utilized in earlier research⁶³. Earlier research have used completely different scoring strategies, such because the immunoreactivity and H-scores, and a variety of cut-off values⁶³. Two current pivotal part III trials (SPOTLIGHT and GLOW) outlined IHC-positivity as moderate-to-strong CLDN18.2 membrane staining in not less than 75% of tumor cells^35,36. A extra detailed dialogue of detection strategies and cut-off values for CLDN18.2-positivity is offered by Mathias-Machado et al.⁶³.

Zolbetuximab is a monoclonal antibody focusing on CLDN18.2³⁵. The worldwide, randomized, double-blind, placebo-controlled part III SPOTLIGHT trial decided the efficacy and security of zolbetuximab plus the modified folinic acid (or levofolinate), fluorouracil, and oxaliplatin routine (mFOLFOX6) vs. placebo plus mFOLFOX6 in CLDN18.2-positive, HER2-negative, superior gastric or GEJ adenocarcinoma within the first-line setting³⁵. Zolbetuximab remedy achieved a major discount within the danger of illness development or loss of life in comparison with placebo (HR = 0.75, 95% CI: 0.60–0.94, P = 0.0066)³⁵. One other international, randomized, double-blind part III trial (GLOW) in contrast zolbetuximab plus capecitabine and oxaliplatin (CAPOX) vs. placebo plus CAPOX in the same affected person inhabitants as SPOTLIGHT and concluded that zolbetuximab considerably improved the PFS (median: 8.21 months vs. 6.8 months; HR = 0.687, 95% CI: 0.544–0.866, P = 0.0007) and OS (median: 14.39 months vs. 12.16 months; HR = 0.771, 95% CI: 0.615–0.965, P = 0.0118) in comparison with placebo³⁶. The Japan Prescribed drugs and Medical Gadgets Company permitted zolbetuximab for treating CLDN18.2-positive, unresectable superior or recurrent gastric most cancers in March 2024¹⁷. The FDA permitted zolbetuximab with chemotherapy for treating gastric or GEJ adenocarcinoma in October 2024, along with approval for the companion diagnostic check utilizing the VENTANA CLDN18 (43-14A) RxDx assay¹⁸. Different anti-CLDN18.2 brokers, similar to osemitamab and SOT102, are additionally beneath growth⁶³. Figure 2 summarizes all biomarkers reviewed herein.

MET

MET is a receptor tyrosine kinase with hepatocyte progress issue (HGF) because the ligand. HGF/MET signaling prompts downstream PI3K/AKT/mTOR and RAS/RAF/MEK/ERK pathways and contributes to vital processes, together with embryogenesis, tissue regeneration, survival, and migration (Figure 2)^8,66,67. Nonetheless, mounting proof means that MET additionally participates in tumor proliferation, invasion, and metastasis in a number of most cancers sorts^66,68. The commonest varieties of MET alterations in gastric most cancers are protein overexpression (39%–60%) and gene amplification (4%–7%)^69–72. These alterations are antagonistic prognostic elements for gastric most cancers. A meta-analysis that included 2,258 gastric most cancers sufferers from 14 research confirmed that in comparison with sufferers with out MET overexpression or MET amplification, the HR for mortality was 2.42 (95% CI: 1.66–3.54) for sufferers with MET overexpression and a pair of.82 (95% CI: 1.86–4.27) for sufferers with MET amplification⁷³.

MET overexpression is set utilizing IHC, whereas MET amplification may be assessed utilizing both fluorescence ISH (FISH) or NGS. Nonetheless, regardless of quite a few previous and ongoing research on anti-MET therapies in gastric most cancers, the shortage of established thresholds for predicting responsiveness to focused therapies stays an issue for MET overexpression and MET amplification⁶⁷. Neither the definitions of MET overexpression IHC scores nor the cut-off values have been standardized, as highlighted by Peng et al.⁶⁷. The identical is true for MET amplification, with various standards, similar to MET/centromere 7 ≥ 2.0 or ≥ 2.2, being utilized in completely different research⁷².

Savolitinib, an anti-MET tyrosine kinase inhibitor (TKI), has demonstrated beneficial efficacy and security in superior gastric most cancers sufferers with MET amplification in a number of part II trials^37,74. For instance, savolitinib monotherapy achieved a 50% goal response fee (ORR) amongst 20 MET-amplified sufferers within the VIKTORY umbrella trial, which was the very best throughout the completely different biomarker-specific remedy arms within the umbrella trial. For sufferers with a MET gene copy quantity > 10, a fair greater ORR of 70% was achieved³⁷. The Chinese language Nationwide Medical Merchandise Administration granted a breakthrough remedy designation in August 2023 for savolitinib in sufferers with MET-amplified domestically superior or metastatic gastric or GEJ most cancers who failed not less than two strains of normal therapies⁷⁵. Within the ongoing part II NCT04923932 trial of savolitinib in MET-amplified domestically superior/metastatic gastric or GEJ most cancers, pre-specified interim analyses demonstrated a confirmed ORR by unbiased evaluation committee of 45%, which reached 50% within the 16 sufferers with excessive MET gene copy quantity⁷⁴. Along with savolitinib, different anti-MET therapies, similar to rilotumumab, are additionally being studied in superior gastric most cancers⁷².

FGFR2

FGFR2 is a transmembrane tyrosine kinase receptor encoded by the FGFR2 gene positioned on chromosome 10q26⁷⁶. The FGFR household of proteins drive downstream pathways, together with the Janus kinase/sign transducer and activator of transcription/interferon regulatory issue (JAK/STAT/IRF), PI3K/mTOR/AKT, and RAS/RAF/MEK/ERK pathways. These pathways regulate vital processes, similar to cell survival, differentiation, and proliferation; dysregulation is related to tumorigenesis and most cancers development^6,12,77 (Figure 2). As such, the FGFR pathway has emerged as a possible remedy goal in a number of cancers⁷⁷. Of be aware, FGFR2 amplification is the most typical kind of FGFR gene aberration and has been related to gastric most cancers, particularly the diffuse subtype⁷⁷. Relying on the testing strategies used and the examine inhabitants, the proportion of gastric most cancers sufferers with FGFR2 amplification ranges from 2%–9%⁷⁷. Meta-analyses have proven that sufferers with FGFR2 amplification or FGFR2 overexpression have considerably worse survival than sufferers with out FGFR2 amplification or FGFR2 overexpression (amplification: HR = 2.09, 95% CI: 1.68–2.59, P P 76.

ISH and NGS can be utilized to detect FGFR2 amplification and IHC can be utilized to detect FGFR2 overexpression¹². Because of the low frequency of FGFR2 amplification and the time and expense concerned for genetic testing, it could be extra environment friendly in medical follow to stratify gastric most cancers sufferers who might profit from anti-FGFR2 therapies based mostly on IHC¹². FGFR2 amplification and FGFR2 overexpression have been used as inclusion standards in medical trials of anti-FGFR2 therapies, with various definitions and cut-off values⁷⁷. For instance, the FIGHT trial for bemarituzumab, a monoclonal antibody towards FGFR2b, enrolled sufferers with FGFR2b overexpression (outlined as IHC2+/3+) or FGFR2 amplification [by circulating tumor DNA (ctDNA)]³⁸, whereas the sooner SHINE trial for AZD4547, an FGFR1/2/3 TKI, included gastric most cancers sufferers displaying FGFR2 polysomy or amplification (outlined as an FGFR2/centromere 10 ratio ≥ 2 or FGFR2 gene clusters in ≥ 10% of tumor cells)⁷⁸.

Bemarituzumab is a first-in-class monoclonal antibody towards FGFR2b³⁸. Within the exploratory part II FIGHT trial enrolling FGFR2b-selected gastric or GEJ adenocarcinoma sufferers who had not been handled with FGF-FGFR pathway inhibitors, the 77 sufferers handled with bemarituzumab had a numerically longer median PFS in comparison with the 78 sufferers handled with matched placebo plus mFOLFOX6 (9.5 months vs. 7.4 months, HR = 0.68, 95% CI: 0.44–1.04, P = 0.073)³⁸. Though this end result was not statistically vital, a confirmatory part III trial (FORTITUDE-101, NCT05052801) with adequate statistical energy is at present underway⁷⁹.

HER2-low

Whereas previous research primarily targeted on HER2-positive (IHC3+ or IHC2+/ISH+, also referred to as HER2-high) sufferers, a major proportion of gastric most cancers sufferers are HER2-low (IHC1+ or IHC2+/ISH-) and exhibit distinct clinicopathologic options in comparison with HER2-negative and -positive sufferers^80,81. A retrospective evaluation of the DESTINY-Gastric01 trial reported an estimated HER2-low prevalence of 28.3%, starting from 19.1%–40.6% throughout completely different examine centres⁸². Greater proportions (40%–60%) of HER2-low expression have additionally been reported in different research⁸⁰. Importantly, among the many 45 sufferers with HER2-low (cohort 1: IHC2+/ISH-, n = 21; cohort 2: IHC1+, n = 24), domestically superior or metastatic gastric or GEJ adenocarcinoma enrolled in DESTINY-Gastric01, trastuzumab deruxtecan remedy achieved 26.3% and 9.5% confirmed ORRs in cohorts 1 and a pair of, respectively; 68.4% and 60.0% of sufferers in cohorts 1 and a pair of skilled tumor dimension reductions, respectively⁸³. These outcomes have offered preliminary proof for the medical exercise of anti-HER2 remedy, even in HER2-low gastric most cancers sufferers, warranting extra randomized managed trials in bigger cohorts to discover the potential advantage of anti-HER2 remedy on this group of sufferers. On a associated be aware, a current growth in breast most cancers has been the popularity by the American Society of Medical Oncology-School of American Pathologists (ASCO-CAP) tips of the medical advantage of trastuzumab deruxtecan as demonstrated in HER2-low metastatic breast most cancers sufferers in DESTINY-Breast04⁸⁴. The 2023 replace of the rules acknowledges a brand new indication for trastuzumab in breast most cancers sufferers with HER2 IHC1+ or IHC2+/ISH- and spotlight the relevance of distinguishing between HER2 IHC1+ and IHC0⁸⁵.

Epstein-Barr virus (EBV)

EBV-positive gastric most cancers is a definite gastric most cancers subtype and accounts for roughly 10% of gastric most cancers instances^16,86. EBV might contribute to gastric most cancers via completely different oncogenic results. Of specific significance, EBV-positive gastric most cancers sometimes reveals elevated expression of PD-L1, which is mediated via the JAK/STAT/IRF pathway (Figure 2)⁸. The usual detection methodology for EBV is EBV-encoded RNA (EBER) ISH⁸⁶, whereas different strategies, similar to NGS and quantitative PCR, are additionally being explored^87,88. Sufferers with EBV-associated gastric most cancers are inclined to show distinct immune traits, together with elevated PD-L1 expression and heightened expression of immune checkpoint markers, such that sufferers with EBV-associated gastric most cancers are prone to profit from remedy with ICI^6,47,86. Importantly, current information recommend that EBV standing could also be predictive of remedy responses to immunotherapy. For instance, in a potential part II medical trial involving 61 sufferers with metastatic gastric most cancers, pembrolizumab as salvage remedy achieved a 100% ORR among the many six sufferers with EBV-positive tumors, with a median response period of 8.5 months⁸⁹. A potential observational examine carried out in China enrolled 9 sufferers with EBV-positive gastric carcinoma who have been handled with immunotherapy⁹⁰. Three of those sufferers achieved a partial response, 5 had steady illness, whereas the remaining affected person with no measurable lesions had decreases in ascites and tumor marker ranges⁹⁰. The longest response period was 18 months on the time of the final follow-up analysis⁹⁰. In a newer examine, Bai et al.⁸⁷ reported that EBV was as efficient as dMMR in predicting responses to ICIs. An ORR of 54.5% was achieved amongst EBV-positive/MRR proficient gastric most cancers sufferers on immunotherapy⁸⁷. Whereas testing for EBV standing just isn’t at present beneficial for routine medical care¹⁶, these outcomes have demonstrated the potential of EBV standing within the medical worth of immunotherapy.

Tumor-infiltrating lymphocytes (TILs)

TIL is an rising biomarker that may be assessed along with PD-L1^6,12. Elevated TIL expression is commonly recognized in EBV-positive and MSI-high gastric most cancers sufferers^6,12. It has been proven that the TIL profile might assist predict remedy responses to immunotherapy. For instance, Chen et al.⁹¹ established a multi-dimensional TIL signature based mostly on the presence of CD4⁺FoxP3⁻PD-L1⁺, CD8⁺PD-1⁻LAG3⁻, and CD68⁺STING⁺ cells and the spatial organisation of CD8⁺PD-1⁺LAG3⁻ T cells, and reported that the TIL signature was related to remedy responses to anti-PD-1/PD-L1 remedy and affected person survival. A current post-hoc evaluation of the CLASSIC trial confirmed that TIL standing additionally predicted the good thing about adjuvant chemotherapy⁹². Stage II-III gastric most cancers sufferers with low TIL density achieved longer disease-free survival if handled with adjuvant chemotherapy along with surgical procedure in comparison with surgical procedure alone⁹². Due to this fact, TIL could also be a worthwhile biomarker for future analysis. TIL remedy, an adoptive remedy based mostly on TIL remoted from resected tumor specimens, is at present being explored⁶.

Different novel biomarkers

Other than the abovementioned biomarkers, a number of different novel biomarkers have emerged as potential targets for the event of recent focused therapies for gastric most cancers, together with dickkopf-1 (DKK1), V-domain immunoglobulin-containing suppressor of T-cell activation (VISTA), B7-H3, and aquaporin-5 (Table 2)^94,97,98,103. DKK1, a secretory protein first recognized as a head inducer throughout embryogenesis¹⁰⁵, can bind to low-density lipoprotein receptor-related protein 5/6 and Frizzled to inhibit Wnt/β-catenin signaling, which is a necessary pathway concerned in cell proliferation, migration, and loss of life⁸. DKK1 has additionally been discovered to advertise epithelial-to-mesenchymal transition and cisplatin resistance in gastric most cancers by activating the phosohatidylinositol 3-kinase/protein kinase B (PI3K/AKT) pathway⁹³. Moreover, DKK1 promotes tumor immune invasion and hinders anti-PD-1 remedy by inducing immunosuppressive macrophages in gastric most cancers⁹⁴. DKN-01 is a DKK-1 neutralizing antibody. The mix of DKN-01 with pemprolizumab was reported to be well-tolerated in a earlier part Ib examine⁹⁵. Within the current part IIa open-label trial, DKN-01 together with chemotherapy and tislelizumab was additionally well-tolerated in sufferers with superior gastroesophageal adenocarcinomas⁹⁶. A randomized part II trial of DKN-01 is at present ongoing⁹⁶. VISTA is expressed on a number of varieties of immune cells, similar to macrophages and dendritic cells, and VISTA-induced T-cell activation is non-redundant from the PD-1/PD-L1 pathway, making VISTA a promising goal for immunotherapy⁹⁸. A part I/II trial of a novel anti-VISTA monoclonal antibody is at present ongoing⁹⁹. The invention of novel biomarkers will reveal extra alternatives to advance take care of gastric most cancers sufferers.

Sampling methodology: tissue vs. liquid biopsy

Regardless of being the gold normal for gastric most cancers testing and analysis, tissue biopsy has a number of notable drawbacks, together with invasiveness, ache, and value^19,20. Moreover, a single tissue biopsy is often inadequate to seize tumor heterogeneity, thus limiting the data tissue biopsy can present (Figure 3)^19,20.

Determine 3

Challenges and future instructions of biomarker testing and biomarker-guided remedy. Molecular testing and focused therapies for gastric most cancers face a number of vital challenges: 1) Conventional tissue biopsy is invasive and dear. 2) Important testing strategies could also be restricted by inter-observer variability (similar to for IHC) or excessive value and lengthy turnaround time (similar to for NGS). 3) Lack of unified, clinically validated cut-off values might hinder the efficient utility of some biomarkers. 4) Tumor heterogeneity, each spatial and temporal, might have an effect on the efficacy of biomarker-guided remedy. Novel testing strategies and remedy methods might assist overcome a few of these challenges: 1) Lipid biopsy presents a non-invasive different to tissue biopsy. 2) AI could also be employed to enhance picture evaluation and reduce subjectivity. 3) Multiplex IHC permits the simultaneous detection of a number of biomarkers, offering a extra complete tumor profile. 4) Ongoing medical trials are additionally exploring mixture remedy to handle heterogeneity and remedy resistance. AI, synthetic intelligence; IHC, immunohistochemistry; NGS, next-generation sequencing.

Testing strategies and diagnostic cut-off values

The success of biomarker-guided remedy hinges closely on precisely figuring out sufferers with particular biomarker expression¹¹¹. At the moment beneficial testing strategies embrace IHC, ISH, PCR, and NGS¹⁶. In response to the NCCN tips, IHC, ISH, and focused PCR ought to be thought-about first for identification of biomarkers earlier than NGS, whereas complete genomic profiling through a validated NGS assay ought to be thought-about if restricted tissue is out there or if the affected person is unable to bear a conventional biopsy, such that sequential testing of single biomarkers and restricted diagnostic panels will exhaust the pattern¹⁶. Nonetheless, vital challenges persist in each the testing strategies and willpower of cut-off values for biomarker expression. For instance, IHC is often used to evaluate protein overexpression based mostly on a semiquantitative scoring system (0, 1+, 2+, and three+)²¹, however the definitions of values on this four-point scale might fluctuate throughout research and have to be additional specified⁶⁷. Even when scores are well-defined, the semiquantitative methodology implicates subjective judgment, which might result in substantial inter- and intra-observer variability and sometimes requires well-trained pathologists with years of expertise²¹. Other than the inherent accuracy and reliability of testing strategies, the accessibility and timeliness of such molecular testing strategies may additionally restrict utility.

Furthermore, the cut-off values for biomarker positivity by IHC and/or genetic testing, similar to FISH, NGS, and PCR, have to be clinically validated and sometimes take time to evolve. Utilizing the established biomarker, HER2, for instance, earlier research, such because the ToGA trial (revealed in 2010) outlined HER2-positivity as IHC3+ or an HER2:CEP17 ratio of ≥ 2 by FISH³¹, whereas newer research, similar to DESTINY-Gastric01 and DESTINY-Gastric02, and present tips have outlined HER2-positivity as IHC3+ or IHC2+/ISH+^16,29. Equally, for PD-L1, though the NCCN tips for gastric most cancers advocate using CPS, the tumor proportion rating (TPS) can be generally utilized in analysis and/or medical follow, particularly in non-small cell lung most cancers^112,113. Moreover, using completely different assays for a similar biomarker assemble might yield disparate outcomes¹¹³. Not surprisingly, this lack of unified, clinically validated cut-off values is much more pronounced for rising biomarkers. Peng et al.⁶⁷ offered an in depth dialogue of the various definitions of MET overexpression by IHC utilized in medical research over time, highlighting the continuing analysis for an optimum, unified threshold. This lack of unified cut-off values might result in inconsistent outcomes throughout completely different research and render the proof generated ineffective for informing biomarker-guided remedy selections. Moreover, given the excessive molecular heterogeneity and complicated immunologic profiles of gastric most cancers³⁹, the expression of a single biomarker could also be insufficient to information remedy selections.

Tumor heterogeneity and remedy resistance

Tumor heterogeneity is among the most elementary options of malignancies¹²⁴. Previous research have underscored the numerous spatial and temporal heterogeneity noticed in gastric most cancers^39,124,125. For instance, within the part II expansion-platform trial PANGEA, 49% of sufferers skilled a shift to a special biomarker group from baseline upon development after first-line remedy, with a further 48% present process a change within the assigned remedy group after second-line remedy¹²⁶. This in depth tumor heterogeneity might have contributed to remedy resistance and failures in biomarker-guided medical trials^39,125, and must be addressed to enhance the prognosis of sufferers with gastric most cancers.