Differential radiographic appearance of BRAF V600E mutant metastatic colorectal cancer (mCRC) in patients matched by primary tumor location.

Abstract

554 Background: BRAF mutation status and location of CRC primary each correlate with pattern of metastatic spread. We sought to determine whether presence of a BRAF V600E (BRAF) mutation is differentially associated with sites and appearance of metastatic disease in patients matched by primary tumor location. Methods: 40 patients with BRAF mutant mCRC were matched to 80 patients with BRAF wild-type CRC by location of primary tumor (right colon, left colon or rectum), sex, and age ( < 50; 50+). CT scans were reviewed for disease characterization. BRAF mutation status, clinicopathological characteristics, and sites of metastatic disease were associated using proportion tests. Results: Of the 120 matched patients,60% were female. The distribution of primary tumor locations was: 60% right colon, 30% left colon, and 10% rectum. Median age at diagnosis was 57, range 20-88 yrs. Significantly higher frequencies of peritoneal metastases (p = 0.045) and ascites (p = 0.0038) occurred in patients with BRAF mutant tumors. Among patients with right colon primaries, no significant difference in sites of disease by BRAF mutation status was observed. In patients with left colon primaries, BRAF mutations associated with less frequent liver metastases (42% vs. 79%, p = 0.024) and more frequent ascites (58% vs. 12%, p = 0.0038). Disease was not measurable by RECIST version 1.1 criteria in 20% of patients with BRAF mutations, most often with peritoneal metastases and ascites. Conclusions: Presence of a BRAF V600E mutation associated with a greater proportion of peritoneal metastases and ascites, even among patients matched for primary tumor location. Of 20 patients with BRAF mutant mCRC and peritoneal metastases plus ascites, 6 patients (30%) had disease that was not measurable by RECIST version 1.1. Radiographic characterization provides a window on BRAF mutant mCRC biology and also reveals a challenge for response evaluation on clinical trials. [Table: see text]