Reduced-dose combination chemotherapy (S-1 plus oxaliplatin) versus full-dose monotherapy (S-1) in older vulnerable patients with metastatic colorectal cancer (NORDIC9): a randomised, open-label phase 2 trial.

BACKGROUND: Older or vulnerable patients with metastatic colorectal cancer are seldom included in randomised trials. The multicentre NORDIC9 trial evaluated reduced-dose combination chemotherapy compared with full-dose monotherapy in older, vulnerable patients.

METHODS: This randomised, open-label phase 2 trial was done in 23 Nordic oncology clinics and included patients aged 70 years or older with previously untreated metastatic colorectal cancer who were not candidates for full-dose combination chemotherapy. Patients were block randomised (1:1) using a web-based tool to full-dose S-1 (30 mg/m2 orally twice daily on days 1-14 every 3 weeks) followed by second-line treatment at progression with irinotecan (250 mg/m2 intravenously on day 1 every 3 weeks or 180 mg/m2 intravenously on day 1 every 2 weeks) or reduced-dose combination chemotherapy with S-1 (20 mg/m2 orally twice daily on days 1-14) and oxaliplatin (100 mg/m2 intravenously on day 1 every 3 weeks) followed by second-line treatment at progression with S-1 (20 mg/m2 orally twice daily on days 1-14) and irinotecan (180 mg/m2 intravenously on day 1 every 3 weeks). Use of bevacizumab (7·5 mg/kg intravenously on day 1 of each cycle) was optional. Treatment allocation was not masked and randomisation was stratified for institution and bevacizumab. The primary outcome was progression-free survival. Survival analyses were by intention to treat and safety analyses were done on the treated population. This trial is registered with EudraCT, number 2014-000394-39, and is closed to new participants.

FINDINGS: From March 9, 2015, to Oct 11, 2017, 160 patients with a median age of 78 years (IQR 76-81) were randomly assigned to full-dose monotherapy (n=83) or reduced-dose combination chemotherapy (n=77). At data cutoff (Sept 1, 2018; median follow-up 23·8 months [IQR 18·8-30·9]), 81 (98%) patients in the full-dose monotherapy group and 71 (92%) patients in the reduced-dose combination group had progressed or died. Median progression-free survival was significantly longer with reduced-dose combination chemotherapy (6·2 months [95% CI 5·3-8·3]) than with full-dose monotherapy (5·3 months [4·1-6·8]; hazard ratio [HR] 0·72 [95% CI 0·52-0·99]; p=0·047). Toxicity was evaluated in 157 patients who received treatment. Significantly more patients in the full-dose monotherapy group (51 [62%] of 82 patients) experienced at least one grade 3-4 adverse event than in the reduced-dose combination group (32 [43%] of 75 patients; p=0·014). Grade 3-4 diarrhoea (12 [15%] vs two [3%]; p=0·018), fatigue (ten [12%] vs three [4%]; p=0·083), and dehydration (five [6%] vs none; p=0·060) were more frequent in the full-dose monotherapy group than in the reduced-dose combination group. Treatment-related deaths occurred in three patients during first-line treatment and three patients during second-line treatment (two in the full-dose monotherapy group vs one in the reduced-dose combination group in both cases).

INTERPRETATION: Reduced-dose combination chemotherapy with S-1 and oxaliplatin for older, vulnerable patients with metastatic colorectal cancer was more effective and resulted in less toxicity than full-dose monotherapy with S-1. Reduced-dose combination chemotherapy could be a preferred treatment for this population.

FUNDING: Taiho Pharmaceuticals, Nordic Group, the Danish Cancer Society, the Swedish Cancer Society, Academy of Geriatric Research (AgeCare), and Region of Southern Denmark.