A Clinical Viewpoint on the Use of Targeted Therapy in Advanced Gastric Cancer

The development of therapies for advanced gastric cancer (GC) has made significant progress over the past few years. The identification of new molecules and molecular targets is expanding our understanding of the disease's intricate nature. The end of the classical oncology era, which relied on well-studied chemotherapeutic agents, is giving rise to novel and unexplored challenges, which will cause a significant transformation of the current oncological knowledge in the next few years. The integration of established clinically effective regimens in additional studies will be crucial in managing these innovative aspects of GC. This study aims to present an in-depth and comprehensive review of the clinical advancements in targeted therapy and immunotherapy for advanced GC.

Antibody-drug conjugates in solid tumors: a look into novel targets

Antibody-drug conjugates (ADCs) are a relatively new class of anticancer agents designed to merge the selectivity of monoclonal antibodies with cell killing properties of chemotherapy. They are commonly described as the "Trojan Horses" of therapeutic armamentarium, because of their capability of directly conveying cytotoxic drug (payloads) into the tumor space, thus transforming chemotherapy into a targeted agent. Three novel ADCs have been recently approved, i.e., trastuzumab deruxtecan, sacituzumab govitecan and enfortumab vedotin, respectively, targeting HER2, Trop2 and Nectin4. Thanks to progressive advances in engineering technologies these drugs rely on, the spectrum of diseases sensitive to these drugs as well as their indications are in continuous expansion. Several novel ADCs are under evaluation, exploring new potential targets along with innovative payloads. This review aims at providing a summary of the technology behind these compounds and at presenting the latest ADCs approved in solid tumors, as well as at describing novel targets for ADCs under investigation and new strategies to optimize their efficacy in solid tumors.

Heterogeneity of amplification of HER2, EGFR, CCND1 and MYC in gastric cancer

BACKGROUND

Intra-tumor heterogeneity is a potential cause for failure of targeted therapy in gastric cancer, but the extent of heterogeneity of established (HER2) or potential (EGFR, CCND1) target genes and prognostic gene alterations (MYC) had not been systematically studied.

METHODS

To study heterogeneity of these genes in a large patient cohort, a heterogeneity tissue microarray was constructed containing 0.6 mm tissue cores from 9 different areas of the primary gastric cancers of 113 patients and matched lymph node metastases from 61 of these patients. Dual color fluorescence in-situ hybridization was performed to assess amplification of HER2, EGFR, CCND1 and MYC using established thresholds (ratio ≥ 2.0). Her2 immunohistochemistry (IHC) was performed in addition.

RESULTS

Amplification was found in 17.4% of 109 interpretable cases for HER2, 6.4% for EGFR, 17.4% for CCND1, and 24.8% for MYC. HER2 amplification was strongly linked to protein overexpression by IHC in a spot-by-spot analysis (p < 0.0001). Intra-tumor heterogeneity was found in the primary tumors of 9 of 19 (47.3%) cancers with HER2, 8 of 17 (47.0%) cancers with CCND1, 5 of 7 (71.4%) cancers with EGFR, and 23 of 27 (85.2%) cancers with MYC amplification. Amplification heterogeneity was particularly frequent in case of low-level amplification (<10 gene copies). While the amplification status was often different between metastases, unequivocal intra-tumor heterogeneity was not found in individual metastases.

CONCLUSION

The data of our study demonstrate that heterogeneity is common for biomarkers in gastric cancer. Given that both TMA tissue cores and clinical tumor biopsies analyze only a small fraction of the tumor bulk, it can be concluded that such heterogeneity may potentially limit treatment decisions based on the analysis of a single clinical cancer biopsy.

HER-2/neu overexpression is an independent prognostic factor for intestinal-type and early-stage gastric cancer patients

GOALS

To evaluate the HER-2/neu protein level by immunohistochemistry (IHC) and its gene amplification by fluorescence in situ hybridization (FISH) in gastric cancer samples, and the relevance to the prognosis of gastric cancer patients.

STUDY

HER-2/neu overexpression and gene amplification were examined with semiquantitative standardized IHC in 775 formalin-fixed paraffin-embedded gastric cancer samples, and 252 of these cases were analyzed with FISH.

RESULTS

Of the 775 gastric cancer samples examined by IHC, a total of 88 (11%) cases were positive for HER-2/neu overexpression at a score of 3+; another 44 (6%) cases were equivocal with a score of 2+; and the rest 643 (83%) cases were negative scored as 0/1+. Intestinal-type and early-stage cancers exhibited higher rate of HER-2/neu overexpression than those of diffuse/mixed-type and advanced cancers (P<0.05). Intestinal-type and early-stage cancers with HER-2/neu overexpression also exhibited short 5 year survival rates (21% vs. 47%, P=0.027; 29% vs. 60%, P=0.037) than HER-2/neu-negative cases, but not in the diffuse/mixed-type and advanced stage cancers. By FISH analysis, it was shown that 70% (60/86) of IHC 3+ had HER-2/neu gene amplication. In contrast, only 14% (6/43) of IHC 2+ cases, and 2.5% (3) of the 120 cases with IHC 0/1+ randomly selected showed HER-2/neu gene amplification.

CONCLUSIONS

HER-2/neu overexpression may be used as an independent prognostic factor for intestinal-type and early-stage gastric cancer patients. IHC 3+ and 2+ cases should be further detected by FISH to assess HER-2/neu gene status. Patients with HER-2/neu amplification also might constitute potential candidates for targeted therapy with trastuzumab.

HER2 in gastric cancer: a new prognostic factor and a novel therapeutic target

Gastric cancer is the second leading cause of cancer mortality in the world and its management, especially in advanced stages, has evolved relatively little. In particular, no targeted modality has so far been incorporated to its treatment armamentarium. HER2 overexpression is increasingly recognized as a frequent molecular abnormality, driven as in breast cancer by gene amplification. There is mounting evidence of the role of HER2 overexpression in patients with gastric cancer, and it has been solidly correlated to poor outcomes and a more aggressive disease. Additionally, preclinical data are showing significant antitumor efficacy of anti-HER2 therapies (particularly monoclonal antibodies directed towards the protein) in in vitro and in vivo models of gastric cancer. As a result, several clinical trials are exploring in different settings and with diverse designs the potential of anti-HER2 therapies in gastric cancer patients. This review summarizes the rationale, preclinical evidence, retrospective clinical analyses, and the interim clinical data pertaining HER2 therapies in gastric cancer.