Survival of patients with deficient mismatch repair metastatic colorectal cancer in the pre-immunotherapy era.

BACKGROUND: Metastatic colorectal cancer patients with deficient mismatch repair (dMMR mCRC) benefit from immunotherapy. Interpretation of the single-arm immunotherapy trials is complicated by insignificant survival data during systemic non-immunotherapy. We present survival data on a large, comprehensive cohort of dMMR mCRC patients, treated with or without systemic non-immunotherapy. METHODS: Two hundred and eighty-one dMMR mCRC patients (n = 54 from three prospective Phase 3 CAIRO trials; n = 227 from the Netherlands Cancer Registry). Overall survival was analysed from diagnosis of mCRC (OS), from initiation of first-line (OS1) and second-line (OS2) systemic treatment. Cox regression analysis examined prognostic factors. As comparison for OS 2746 MMR proficient mCRC patients were identified. RESULTS: Of 281 dMMR patients, 62% received first-line and 26% second-line treatment. Median OS was 16.0 months (13.8-19.6) with antitumour therapy and 2.5 months (1.8-3.5) in untreated patients. OS1 was 12.8 months (10.7-15.2) and OS2 6.2 months (5.4-8.9) in treated dMMR patients. Treated dMMR patients had a 7.6-month shorter median OS than pMMR patients. CONCLUSION: Available data from immunotherapy trials lack a control arm with standard systemic treatment. Given the poor outcome compared to the immunotherapy results, our data strongly suggest a survival benefit of immunotherapy in dMMR mCRC patients.

The Role of Intestinal Microbiota in Metastatic Colorectal Cancer Patients Treated With Capecitabine.

BACKGROUND: Previous pre-clinical research has indicated that the intestinal microbiota can potentiate anti-tumour efficacy of capecitabine and that capecitabine treatment impacts intestinal microbiota composition and diversity. Using a longitudinal design, this study explores the associations between the intestinal microbiota and treatment response in patients with metastatic colorectal cancer (mCRC) during capecitabine treatment. PATIENTS AND METHODS: Patients with mCRC treated with capecitabine were prospectively enrolled in a multicentre cohort study. Patients collected a faecal sample and completed a questionnaire before, during, and after three cycles of capecitabine. Several clinical characteristics, including tumour response, toxicity and antibiotic use were recorded. Intestinal microbiota were analysed by amplicon sequencing of the 16S rRNA V4 gene-region. RESULTS: Thirty-three patients were included. After three cycles of capecitabine, six patients (18%) achieved a partial response, 25 (76%) showed stable disease, and one (3%) experienced progressive disease. Of the 90 faecal samples were collected. Microbial diversity (α-diversity), community structure (ß-diversity), and bacterial abundance on phylum and genus level were not significantly different between responders and non-responders and were not significantly affected by three cycles of capecitabine. CONCLUSION: This is the first clinical study with longitudinal intestinal microbiota sampling in mCRC patients that explores the role of the intestinal microbiota during treatment with capecitabine. Intestinal microbiota composition and diversity before, during, and after three cycles of capecitabine were not associated with response in this study population. Capecitabine did not induce significant changes in the microbiota composition and diversity during the treatment period. Individual effects of antibiotics during capecitabine treatment were observed.