Despite the high morbidity and mortality of metastatic colorectal cancer (mCRC) in older patients, they have been underrepresented in clinical trials and their optimal treatment is yet to be determined. This open-label phase II study evaluated the benefits of panitumumab and capecitabine as a first-line chemotherapy regimen in older patients with wild-type [WT] RAS mCRC.

Patients (≥70 years; ECOG≤2) received 3-week cycles of panitumumab (9 mg/kg on day 1) plus capecitabine (850 mg/m twice daily on days 1-14) until disease progression or unacceptable toxicity. Response was evaluated every 9 weeks according to RECIST_1.1. Outcome measures were: objective response rate (ORR), duration of response (DoR), time to response (TTR), progression (TTP) and treatment failure (TTF), progression-free survival (PFS), overall survival (OS), and safety.

Twenty-seven patients (11 women; median age: 78 years; ECOG: 0 [26%], 1 [67%], 2 [7%]) were evaluated. Median follow-up was 17.7 months. Confirmed ORR (95%CI) was 44.4% (25.7-63.2), with 25.9% of patients achieving at least stable disease. Median (95%CI) DoR was 8.7 (5.5-10.4) months, and median TTR was 2.2 (1.9-2.8) months. Median TTP was 9.6 (4.8-11.5) months, with a median TTF of 5.2 (2.8-7.2) months. The median PFS was 7.5 (4.4-10.4) months, and the median OS was 23.7 (7.4-27.5) months. Seventeen (63%) patients reported panitumumab and/or capecitabine-related adverse events grade 3-4, with skin toxicity (18.5%) being the most common. Two (7.4%) deaths were treatment-related.

This study suggests that panitumumab plus capecitabine is a safe and effective regimen in older patients with WT RAS mCRC.