An international phase III randomised (1:1) non-inferiority trial comparing 3 versus 6 months of oxaliplatin based adjuvant chemotherapy for colorectal cancer is reported at this years ESMO Congress in Madrid.

For more on the duration of therapy for colorectal cancer, studied through the umbrella IDEA trial group, read about the ESMO debate here

Results presented earlier this year at ASCO 2017 gave conflicting results as to whether 3 months adjuvant chemotherapy was non-inferior to 6 months treatment.

The effect of treatment duration on DFS appeared to depend on the chemotherapy regimen (Capox or FOLFOX) chosen and on risk group (high-risk [T4 or N2] vs low-risk [T1-3 N1]) stage lll disease.

SCOT is a non-inferiority randomised study designed to determine whether 3 months of adjuvant chemotherapy with FOLFOX or Capox (physician/patient choice) in Stage lll/high risk Stage ll colorectal cancer is as effective as 6 months treatment.

Non-inferiority was determined to be a maximum 2.5% fall in 3-year disease-free survival (DFS) on the 3 month arm (from 78% on the 6 month arm).

The study was designed with 90% power at the 2.5% L-sided level of statistical significance and aimed to recruit 9500 patients to observe 2,750 DFS events (relapses/deaths/new colorectal cancers).

6088 patients with Stage lll/high risk Stage ll cancers of the colon or rectum were randomised between 27th March 2008 and 29th November 2013.

1981 patients received FOLFOX and 4107 received Capox.

For 3 year DFS there were 1482 events (740 in the 3 month arm and 742 in the 6 month arm).

3 year DFS was 76.7% for the 3 month arm and 77.1% for the 6 month arm (HR 1.008, for non-inferiority p=0.014).

Non-inferiority was stronger for Capox than FOLFOX but the choice of regimen was not randomised.

Further analysis looking at dose intensity of chemotherapy received and the effect of age and gender will be presented.

The updated SCOT results will allow further insight into treatment decisions for the duration of adjuvant therapy of colorectal cancer with regard to adjuvant chemotherapy regimen used and the risk of recurrence.

Source: ESMO 2017 Congress