Cure Is Possible: Extensively Metastatic HER2-Positive Gastric Carcinoma with 5 years of Complete Remission after Therapy with the FLOT Regimen and Trastuzumab

Comprehensive biomarker analysis of long-term response to trastuzumab in patients with HER2-positive advanced gastric or gastroesophageal adenocarcinoma

BACKGROUND

A subgroup of patients with HER2-positive metastatic gastric and gastroesophageal junction cancers shows long-term response under trastuzumab maintenance monotherapy. Obviously, HER2 status alone is not able to identify these patients. We performed this study to identify potential new prognostic biomarkers for this long-term responding patient group.

PATIENTS AND METHODS

Tumour samples of 19 patients with HER2-positive metastatic gastric and gastroesophageal junction cancer who underwent trastuzumab treatment were retrospectively collected from multiple centres. Patients were divided into long-term responding (n = 7) or short-term responding group (n = 12) according to progression-free survival (PFS≥12 months vs. PFS < 12 months). Next-generation sequencing and microarray-based gene expression analysis were performed along with HER2 and PD-L1 immunohistochemistry.

RESULTS

Long-term responding patients had significantly higher PD-L1 combined positive scores (CPS) and CPS correlated with longer progression-free survival. PD-L1 positivity (CPS ≥ 1) was further associated with an increased CD4+ memory T-cell score. The ERBB2 copy number as well as the tumour mutational burden could not discriminate between short-term and long-term responding patients. Genetic alterations and coamplifications in HER2 pathway associated genes such as EGFR, which were connected to trastuzumab resistance, were present in 10% of the patients and equally distributed between the groups.

CONCLUSION

The study highlights the clinical relevance of PD-L1 testing also in the context of trastuzumab treatment and offers a biological rational by demonstrating elevated CD4+ memory T-cells scores in the PD-L1-positive group.

Third- and Late Line Treatments of Metastatic Gastric Cancer: Still More to Be Done

In recent years, advances of anticancer and supportive therapies have determined a gradual improvement in survival rates and patients’ general conditions in metastatic gastric cancer (mGC), allowing them to receive further treatments. The choice of treatment is driven by performance status, age, stage of disease, number of metastatic sites and time from the first to third line of treatment. Targets such as microsatellite instability, PD-L1 expression, and HER2 overexpression or amplification may be addressed to personalise treatment and prolong survival. Despite a growing number of third line options that have provided clinicians with greater opportunities to customise treatments, up to date few agents have been demonstrated as effective after two standard lines for mGC; for these reasons, chemotherapy, immunotherapy, and targeted therapy were all widely investigated in both phase II and phase III studies. Overall, TAS-102, apatinib, regorafenib, nilotinib, trastuzumab, and pembrolizumab were demonstrated to be valid options in the third line scenario for mGC patient refractory to at least two lines of therapy. A multimodal approach based on chemotherapy, immunotherapy, targeted agents, a personalised nutritional programme as well as the research of new predictive biomarkers may pave the way to new strategies to identify the best treatment for each patient.