In the German phase II PANAMA trial reported in the Journal of Clinical Oncology, Modest et al found that the addition of the monoclonal antibody panitumumab to fluorouracil (5-FU)/leucovorin maintenance therapy improved progression-free survival in patients with RAS wild-type metastatic colorectal cancer.
In the open-label multicenter trial, 248 patients with stable disease or objective response after first-line induction with six cycles of 5-FU/leucovorin and oxaliplatin plus panitumumab were randomly assigned between May 2014 and February 2021 to receive maintenance panitumumab with 5-FU/leucovorin (n = 125) or 5-FU/leucovorin (n = 123). 5-FU/leucovorin and oxaliplatin plus panitumumab was given once every 2 weeks for six cycles, consisting of oxaliplatin at 85 mg/m2, leucovorin at 400 mg/m2, 5-FU at 2,400 mg/m2 (one dose administered over 48 hours), and panitumumab at 6 mg/kg body weight until disease progression or unacceptable toxicity. The primary endpoint was progression-free survival.
At data cutoff, median follow-up was 36 months. Median progression-free survival was 8.8 months (80% confidence interval [CI] = 7.6–10.2 months) in the panitumumab group vs 5.7 months (80% CI = 5.6–6.0 months) in the control group (hazard ratio [HR] = 0.72, 80% CI = 0.60–0.85, P =.014).
Objective response rates during maintenance were 40.8% vs 26.0% (odds ratio = 1.96, 95% CI = 1.14–3.36, P = .02). Median overall survival was 28.7 months (95% CI = 25.4–39.1 months) in the panitumumab group vs 25.7 months (95% CI = 22.2–28.2 months) in the control group (HR = 0.84, 95% CI = 0.60–1.18, P = .32).
Grade 3 or 4 adverse events during maintenance therapy occurred in 43.2% of the panitumumab group vs 26.0% of the control group. The most common in the panitumumab group were rash (7.2% vs 0% control group) and hypomagnesemia (6.4% vs 0%). Serious adverse events occurred in 12.8% vs 10.6% of patients.
The investigators concluded, “In RAS wild-type metastatic colorectal cancer, maintenance therapy with [5-FU/leucovorin] plus panitumumab induced a significantly superior progression-free survival compared with [5-FU/leucovorin] alone. If active maintenance therapy is aspired following induction therapy with [5-FU/leucovorin] and oxaliplatin plus panitumumab, [this regimen] appears to be the most favorable option.”
Dominik Paul Modest, MD, of the Department of Hematology, Oncology, and Tumorimmunology, Charité-Universitätsmedizin Berlin, is the corresponding author for the Journal of Clinical Oncology article.
Disclosure: The study was funded by AIO Studien gGmbH and Amgen Inc. For full disclosures of the study authors, visit ascopubs.org.The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.