Durable Clinical Response to Immune and Targeted Therapies in an Elderly Man with Synchronous Gastric (HER2+) and Bladder Cancers: Case Report and Literature Review

Abstract

Synchronous occurrences of gastric cancer positive for human epidermal growth factor receptor 2 (HER2+) and bladder cancer are rarely encountered in clinical practice. When and how to effectively treat both tumors, without compounding adverse effects, must be addressed. Herein, we describe an elderly man who presented with both gastric cancer (HER2+) and bladder cancer. Due to enlarged and fused lymph nodal metastasis, he was illsuited for stomach resection. After transurethral resection of the bladder tumor, we administered both chemotherapy and the targeted agent trastuzumab. Gastric cancer showed partial response however bladder cancer recurred following two cycles of this regimen, the adverse effects were prohibitive, prompting refusal of further chemotherapy and radiotherapy. He then received the immune checkpoint inhibitor (ICI) nivolumab and trastuzumab in combination. This particular regimen successfully controlled both cancers and substantially improved the patient's quality of life. Its long-term use did not intensify adverse reactions, enabling a progression-free survival of 21 months to date. We have also reviewed other published clinical strategies applied in rare instances of multiple primary malignancies as a reference for treating such patients.

Case Report: Complete Remission of a Patient With Metastatic Gastric Cancer Treated With Nivolumab Combined With Chemotherapy After Palliative Surgery

“…Moreover, nivolumab monotherapy has been reported to cause serious IRAEs, resulting in the failure of nivolumab restart in tumor recurrence. The combination of extended immunity and targeted therapy does not aggravate the adverse reactions of patients ( 33 ). Therefore, we propose another hypothesis: the combination of drugs can reduce the probability of adverse events caused by nivolumab or delay their occurrence.…”