Trastuzumab, a monoclonal antibody to human epidermal growth factor receptor 2 (HER2), has improved survival in patients with HER2-positive advanced gastric or gastroesophageal junction cancer (AGC). The inevitable development of resistance to trastuzumab remains a problem, however, with several treatment strategies that have proven effective in breast cancer having failed to show clinical benefit in AGC. In this review, we summarize the mechanisms underlying resistance to HER2-targeted therapy and outline past and current challenges in the treatment of HER2-positive AGC refractory to trastuzumab. We further describe novel agents such as HER2 antibody–drug conjugates that are under development and have shown promising antitumor activity in early studies.

Immunotherapy has been shown to prolong survival in recurrent or metastatic squamous cell carcinoma of the head and neck (SCCHN) in front-line use; however, subsequent systemic therapy has not been optimized. This study aimed to evaluate the safety and efficacy of cetuximab-containing chemotherapy after immunotherapy. We retrospectively analyzed patients with recurrent or metastatic SCCHN who underwent cetuximab-containing regimens after progression on immunotherapy. Of the 22 patients who met the inclusion criteria, 21 received paclitaxel and cetuximab, and 1 carboplatin and fluorouracil and cetuximab after immunotherapy. Nine patients achieved a partial response, 10 patients had stable disease as their best response on cetuximab-containing chemotherapy, yielding an overall response rate and disease control rate of 40.9 and 86.4%, respectively. The median progression-free survival was 5.2 months, and the median overall survival was 14.5 months. Ten patients developed grade 3–4 adverse events, including neutropenia (31.8%), acneiform rash (9.1%), anemia (4.5%), hypertransaminasemia (4.5%) and stomatitis (4.5%). The most frequent cetuximab-related toxicities across all grades were skin reactions (77.3%), hypomagnesemia (40.9%), stomatitis (27.3%), paronychia (13.6%) and keratitis (4.5%). There was no treatment-related death. Taken together, cetuximab-containing chemotherapy was effective and feasible even after immunotherapy.

Background: Esophageal cancer is associated with synchronous or metachronous cancer at other primary sites. However, few studies have evaluated the second malignancies after the treatment of esophageal cancer. The present study aimed to clarify the frequency of and risk factors for the second malignancies after definitive therapy for esophageal cancer.Patients and Methods: We included patients with esophageal cancer who received definitive therapy between 2000 and 2010. Exclusion criteria were synchronous cancer or a past history of cancer. Standardized incidence rate (SIR) was calculated using age‐ and sex‐specific incidence rates from the cancer registry data. To conduct risk analyses, we used the competing risk regression model, which defined death and the development of second malignancies as competing risks.Results: A total of 758 patients were included, with 131 second malignancies occurring in 106 patients (14%), over a median follow‐up of 3.7 years. Cumulative incidences of second malignancies after 3, 5, and 8 years were 4.0%, 7.6%, and 13.8%, respectively. The risk of second malignancy was significantly elevated [SIR = 1.83, 95% confidence interval (CI): 1.50‐2.22]. The most common sites of primary tumor were the head and neck (20%), followed by the lung (17%), stomach (16%), colon and rectum (11%), and urinary tract (9%). Risk analyses revealed that age ≥ 65 years [subdistribution hazard ratio (sHR): 1.51, 95% CI: 1.01‐2.24, vs age < 65] and clinical stages 0‐I (sHR: 2.48, 95% CI: 1.46‐4.22, vs stage III and IV) and II (sHR: 2.10, 95% CI: 1.23‐3.58, vs stage III and IV) were significantly associated with second malignancies.Conclusions: Compared with the general population, an increased incidence of second malignancies was observed in the patients with esophageal cancer in the present study even after definitive treatment. Careful follow‐up is required, especially in patients at a higher risk of second malignancies.

PURPOSE: ERBB2 copy number (CN), measured using next-generation sequencing, is a predictive biomarker for trastuzumab efficacy in human epidermal growth factor receptor 2 (HER2)–positive advanced esophagogastric and gastric cancer (AGC). We aimed to investigate the association of ERBB2 amplification and gene coalterations with response and resistance to trastuzumab-combined chemotherapy. METHODS: The SCRUM-Japan GI-SCREEN was a comprehensive genomic profiling project of GI cancer tissues using Oncomine Cancer Research Panel and Oncomine Comprehensive Assay. From 885 patients with AGC who successfully underwent gene profiling, 74 with ERBB2 amplification (CN ≥ 4.0) and who received first-line trastuzumab-combined chemotherapy were selected, and ERBB2 CN and gene coalterations were assessed. RESULTS: ERBB2 CN did not differ in tumor response to trastuzumab-combined chemotherapy (one-way analysis of variance test, P = .37). Multivariate analysis using the Cox proportional hazard model revealed that ERBB2 CN (continuous log₂-converted CN, hazard ratio, 0.76; 95% CI, 0.62 to 0.93; P < .01) and receptor/oncogene amplifications in the HER2 signaling pathway (hazard ratio, 2.5; 95% CI, 1.2 to 5.3; P = .01) were significant predictors for progression-free survival (PFS). ERBB2 variants coexisted in five patients (7%) and were missense mutations. Two patients with low variant allele frequencies (VAFs; 8%, 12%) showed high ERBB2 CN (55, 80) and durable response (≥ 20 months), whereas three patients with high VAFs (66%–90%) showed low ERBB2 CN (8-11) and no response with short PFS (1-10 months). CONCLUSION: ERBB2 CN and gene coamplification in the HER2 signaling pathway were positive and negative predictors of PFS in trastuzumab-treated HER2-positive AGC patients, respectively. HER2-positive AGC patients with a high VAF of ERBB2 showed poor outcomes and may need HER2 tyrosine kinase inhibitors and trastuzumab deruxtecan.

BRAF (v-raf murine sarcoma viral oncogene homolog B1) V600E mutant colorectal cancer is associated with short survival. Recently, clinical trials have been conducted to improve outcomes of second or later lines of chemotherapy. However, there is a paucity of reference data pertaining to outcomes of second-line chemotherapy and prognostic factors that are relevant only to BRAF mutant patients. We retrospectively reviewed metastatic colorectal cancer patients with BRAF V600E mutation who underwent second-line chemotherapy between January 2007 and March 2017. We evaluated treatment outcomes and performed prognostic analyses. A total of 52 patients were included. The median progression-free survival and overall survival (OS) were 2.5 [95% confidence interval (CI) = 1.91–4.11] and 6.5 (95% CI = 4.30–9.63) months, respectively. Overall response and disease control rates were 7% and 48%, respectively. All the regimens which elicited a partial response included BRAF inhibitors in combination with anti-epidermal growth factor receptor (EGFR) antibodies. Therefore, the overall response was 0% after exclusion of patients treated with study drugs. Multivariate analysis for OS revealed that the Glasgow Prognostic Score (GPS), elevated lactate dehydrogenase, and poor performance status were independent prognostic factors. In particular, survival curves according to the GPS stratified the patients into distinct risk groups. The median OSs in patients with GPS of 0, 1, and 2 were 9.9, 5.0, and 1.9 months, respectively. Outcomes of second-line chemotherapy for metastatic colorectal cancer patients with BRAF V600E mutation were extremely poor. GPS may be useful in future clinical trials.