ESMO 2014: Poster Session: MOSAIC study – Actualization of overall survival with a 10-year follow up and evaluation of BRAF (GREGOR investigators)

by Denys Wheatley: The session dealt primarily with the advanced (stage 2 and 3) colon cancer patients who had undergone resection, in a study discussed by Thiery Andre (Paris). Arms in the trials had received flurouracil plus leucovorin (LV5FU2) or LV5FU2 plus oxaliplatin (FOLFOX4), which had already been analysed after 3 years with respect to overall (OS) and disease free survival (DFS). The latter combination had proved beneficial, in particular to dMMR patients. The discussion here was on the 10-year follow-up and the outcomes in cases in which BRAF was assessable from tissue samples for approximately 900 of over 2000 patients in total.  Data from a large number of variables were compared to assess whether any had contributed significantly to DFS. In both stage 2 and 3 cases, BRAF^mut was not predictive of DFS, but dMMR was to a significant extent (for example, DFS at 10-year for Stage 2 was 75.8 vs 70.3 for stage 3 when the mutant was compared with the wild-type gene). Regarding the main two arms, there was significant benefit with FOLFOX4 on DFS (61.7 vs 67.5%; HR 0.82) and OS (67.1 vs 71.7%; HR 0.85). There was discussion regarding such variables as to differences between right and left side tumours, but it seemed this did not essentially give help predict the outcomes in relation to DFS or OS. There was also concern on how long first line treatment was given, and whether EGFR has any role as a marker. In general the conclusion was that progress had been made regarding OS and DFS as reported, with stage 2 showing less benefit than 3. There was comparison with other treatment regimes in trials elsewhere, but little emerged as significantly better.