Clinical case of the neoadjuvant treatment with nivolumab in a patient with microsatellite unstable (MSI-H) locally advanced gastric cancer

HER-2 positive gastric cancer: Current targeted treatments

Gastric cancer (GC) is highly metastatic and characterized by HER2 amplification. Aberrant HER2 expression drives metastasis, therapy resistance, and tumor recurrence. HER2 amplification contributes to drug resistance by upregulating DNA repair enzymes and drug afflux proteins, reducing drug efficacy. HER2 modulates transcription factors critical for cancer stem cell properties, further impacting drug resistance. HER2 activity is influenced by HER-family ligands, promoting oncogenic signaling. These features point to HER2 as a targetable driver in GC. This review outlines recent advances in HER2-mediated mechanisms and their upstream and downstream signaling pathways in GC. Additionally, it discusses preclinical research investigation that comprehends trastuzumab-sensitizing phytochemicals, chemotherapeutics, and nanoparticles as adjunct therapies. These developments hold promise for improving outcomes and enhancing the management of HER2-positive GC.

Long-term survivals of immune checkpoint inhibitors as neoadjuvant and adjuvant therapy in dMMR/MSI-H colorectal and gastric cancers

BACKGROUND

The long-term survival benefit of immune checkpoint inhibitors (ICIs) in neoadjuvant and adjuvant settings is unclear for colorectal cancers (CRC) and gastric cancers (GC) with deficiency of mismatch repair (dMMR) or microsatellite instability-high (MSI-H).

METHODS

This retrospective study enrolled patients with dMMR/MSI-H CRC and GC who received at least one dose of neoadjuvant ICIs (neoadjuvant cohort, NAC) or adjuvant ICIs (adjuvant cohort, AC) at 17 centers in China. Patients with stage IV disease were also eligible if all tumor lesions were radically resectable.

RESULTS

In NAC (n = 124), objective response rates were 75.7% and 55.4%, respectively, in CRC and GC, and pathological complete response rates were 73.4% and 47.7%, respectively. The 3-year disease-free survival (DFS) and overall survival (OS) rates were 96% (95%CI 90-100%) and 100% for CRC (median follow-up [mFU] 29.4 months), respectively, and were 84% (72-96%) and 93% (85-100%) for GC (mFU 33.0 months), respectively. In AC (n = 48), the 3-year DFS and OS rates were 94% (84-100%) and 100% for CRC (mFU 35.5 months), respectively, and were 92% (82-100%) and 96% (88-100%) for GC (mFU 40.4 months), respectively. Among the seven patients with distant relapse, four received dual blockade of PD1 and CTLA4 combined with or without chemo- and targeted drugs, with three partial response and one progressive disease.

CONCLUSION

With a relatively long follow-up, this study demonstrated that neoadjuvant and adjuvant ICIs might be both associated with promising DFS and OS in dMMR/MSI-H CRC and GC, which should be confirmed in further randomized clinical trials.

Heterogeneity and Adjuvant Therapeutic Approaches in MSI-H/dMMR Resectable Gastric Cancer: Emerging Trends in Immunotherapy

Gastric cancer (GC) remains one of the world's most common and fatal malignant tumors. With a refined understanding of molecular typing in recent years, microsatellite instability (MSI) has become a major molecular typing approach for gastric cancer. MSI is well recognized for its important role during the immunotherapy of advanced GC. However, its value remains unclear in resectable gastric cancer. The reported incidence of microsatellite instability-high (MSI-H)/deficient mismatch repair (dMMR) in resectable gastric cancer varies widely, with no consensus reached on the value of postoperative adjuvant therapy in patients with MSI-H/dMMR resectable GC. It has been established that MSI-H/dMMR tumor cells can elicit an endogenous immune antitumor response and ubiquitously express immune checkpoint ligands such as PD-1 or PD-L1. On the basis of these considerations, MSI-H/dMMR resectable GCs are responsive to adjuvant immunotherapy, although limited research has hitherto been conducted. In this review, we comprehensively describe the differences in geographic distribution and pathological stages in patients with MSI-H/dMMR with resectable gastric cancer and explore the value of adjuvant chemotherapy and immunotherapy on MSI-H/dMMR to provide a foothold for the individualized treatment of this patient population.

Complete response to neoadjuvant pembrolizumab and capecitabine in microsatellite stable, Epstein-Barr virus-positive, locally advanced gastric adenocarcinoma: case report

Immunotherapy has been established as a standard in select molecular subgroups of treatment-refractory advanced gastric cancer. However, its role in resectable gastric cancer where perioperative systemic therapy is the standard remains unclear. We present a case of a man who was diagnosed with resectable gastric cancer that was microsatellite stable but programmed death-ligand 1 (PD-L1) and Epstein-Barr Virus (EBV)-positive. Given extenuating circumstances of the SARS-CoV-2 pandemic, preferences to limit exposure to the healthcare setting, and the unique tumor molecular features, neoadjuvant pembrolizumab and capecitabine was pursued after multidisciplinary discussion. He was able to achieve a complete response to this neoadjuvant regimen with no further signs of radiographic or pathologic disease on follow-up. We highlight a dramatic response to this novel approach that represents among the first cases to support a potentially viable neoadjuvant chemoimmunotherapy strategy to resectable gastric cancer. In select patients, perioperative immunotherapy-based therapy may constitute a promising strategy in resectable gastric cancer and warrants further investigation.

Salvage Treatment Using Anti-PD-1/CTLA-4 Immunotherapy After Failure of Neoadjuvant Chemotherapy in Microsatellite Instable Gastroesophageal Carcinoma

Perioperative chemotherapy is standard treatment for patients with early high-risk gastroesophageal adenocarcinoma independent of molecular subtype. Approximately 8% of gastroesophageal cancers have a microsatellite instable phenotype (MSI-H), and retrospective analyses of neoadjuvant/adjuvant chemotherapy trials suggests no survival benefit in this patient population compared with surgery alone. Patients with advanced MSI-H malignancies obtain durable responses with immunotherapy using anti-programmed cell death protein 1 (PD-1) checkpoint blockade. We describe a case of a patient with an early MSI-H gastroesophageal adenocarcinoma who progressed on neoadjuvant chemotherapy precluding subsequent surgical resection. The patient was subsequently treated with immunotherapy using the anti-PD-1 antibody nivolumab and the anti-cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) antibody ipilimumab leading to a complete remission with biopsies of the residual tumor mass and regional lymph nodes revealing no residual tumor. This case highlights the lack of benefit from neoadjuvant chemotherapy in patients with MSI-H gastroesophageal cancers and suggests that perioperative anti-PD-1-based immunotherapy should be further investigated in this patient population. KEY POINTS: This report describes the successful salvage treatment of a patient with an early high-risk MSI-H gastroesophageal carcinoma who progressed through neoadjuvant chemotherapy using combination immunotherapy of the anti-programmed cell death protein 1 (PD-1) antibody nivolumab and the anti-cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) antibody ipilimumab, leading to an ongoing complete remission. The case is in keeping with retrospective analyses of perioperative treatment trials demonstrating a lack of chemotherapy benefit in patients with MSI-H gastroesophageal carcinoma and supports the further investigation of anti-PD-1-based immunotherapy as a treatment modality in this patient population. The case highlights the potential difficulties that may be encountered in the surgical management of patients treated with neoadjuvant immunotherapy with reactive dense fibrotic changes precluding surgical resection.