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Background: Differences between the features of primary cancer and matched metastatic cancer have recently drawn attention in research. This study investigated the concordance in microsatellite instability (MSI) and mismatch repair (MMR) status between primary and corresponding metastatic colorectal cancer (CRC). Methods: Consecutive patients with metastatic CRC who had both primary and metastatic tumors diagnosed at our institution in January 2008 through December 2016 were identified. Immunohistochemistry was used to test the MMR status of both primary and matched metastatic tumors, and PCR analysis was performed to test MSI in patients with deficient MMR (dMMR) status. Results: A total of 369 patients were included. Of the 46 patients with MSI-high primary tumors, 37 (80.4%) also had MSI-high metastatic tumors, whereas 9 (19.6%) had microsatellite stable (MSS) metastatic tumors. A high concordance was found in patients with liver, lung, or distant lymph node metastases. Interestingly, the discrepancy was more likely to be limited to peritoneal (5/20) or ovarian (4/4) metastasis (chi-square test, P<.001). These organ-specific features were also found in the pooled analysis. Along with the change of MSI-high in primary cancer to MSS in metastatic cancer, lymphocyte infiltration decreased significantly (P=.008). However, the change did not influence survival; the median overall survival of MSI-high and MSS metastatic tumors was 21.3 and 21.6 months, respectively (P=.774). The discrepancy rate was 1.6% for patients with proficient MMR primary tumors. Conclusions: For patients with dMMR primary tumors, the concordance of MSI and MMR status in primary CRC and corresponding metastatic cancer is potentially organ-specific. High concordance is found in liver, lung, and distant lymph node metastases, whereas discrepancy is more likely to occur in peritoneal or ovarian metastasis. Rebiopsy to evaluate MSI-high/dMMR status might be needed during the course of anti–PD-1 therapy in cases of peritoneal or ovarian metastasis.

Background: The goal of this study was to explore the value of adding neoadjuvant chemotherapy (NACT) or adjuvant chemotherapy (ACT) to concurrent chemoradiotherapy (CCRT) in patients with nasopharyngeal carcinoma (NPC) with different risks of treatment failure. Patients and Methods: A total of 2,263 eligible patients with stage III–IVb NPC treated with CCRT ± NACT or ACT were included in this retrospective study. Distant metastasis–free survival (DMFS), overall survival, and progression-free survival were calculated using the Kaplan-Meier method and differences were compared using the log-rank test. Results: Patients in the low-risk group (stage N0–1 disease and Epstein-Barr virus [EBV] DNA <4,000 copies/mL) who received NACT followed by CCRT achieved significantly better 5-year DMFS than those treated with CCRT alone (96.2% vs 91.3%; P= .008). Multivariate analyses also demonstrated that additional NACT was the only independent prognostic factor for DMFS (hazard ratio, 0.42; 95% CI, 0.22–0.80; P=.009). In both the intermediate-risk group (stage N0–1 disease and EBV DNA ≥4,000 copies/mL and stage N2–3 disease and EBV DNA <4,000 copies/mL) and the high-risk group (stage N2–3 disease and EBV DNA ≥4,000 copies/mL), comparison of NACT or ACT + CCRT versus CCRT alone indicated no significantly better survival for all end points. Conclusions: The addition of NACT to CCRT could reduce distant failure in patients with low risk of treatment failure.