SPIRITT: A Randomized, Multicenter, Phase II Study of Panitumumab with FOLFIRI and Bevacizumab with FOLFIRI as Second-Line Treatment in Patients with Unresectable Wild Type KRAS Metastatic Colorectal Cancer

In this randomized, phase II estimation trial in which we compared FOLFIRI (irinotecan, 5-fluorouracil, and leucovorin) in combination with panitumumab or bevacizumab in patients with wild type Kirsten rat sarcoma viral oncogene homolog (KRAS) metastatic colorectal cancer with disease progression during oxaliplatin-based chemotherapy and bevacizumab, panitumumab or bevacizumab had similar efficacy in terms of overall and progression-free survival, with expected toxicities. Background: Second-line treatment with chemotherapy and anti-epidermal growth factor receptor or anti-vascular endothelial growth factor antibodies improves outcomes in patients with wild type Kirsten rat sarcoma viral oncogene homolog (KRAS) metastatic colorectal cancer (mCRC). The choice of biological agent in second-line mCRC remains unclear. In this randomized, phase II estimation trial, we compared FOLFIRI (irinotecan, 5-fluorouracil, and leucovorin) in combination with panitumumab or bevacizumab in patients with disease progression during oxaliplatin-based chemotherapy and bevacizumab. Patients and Methods: One hundred eighty-two patients were randomized to FOLFIRI with panitumumab or bevacizumab. The primary end point was progression-free survival (PFS). Secondary end points included overall survival (OS), objective response rate (ORR), and safety. Results: PFS was similar between arms, with a hazard ratio (HR) of 1.01(95% confidence interval [Cl], 0.68-1.50; P =.97). Median PFS was 7.7 months (95% Cl, 5.7-11.8) in the panitumumab arm and 9.2 months (95% Cl, 7.8-10.6) in the bevacizumab arm. OS was also similar between arms, with an HR of 1.06 (95% Cl, 0.75-1.49; P =.75). Median OS was 18.0 months (95% Cl, 13.5-21.7) in the panitumumab arm and 21.4 months (5% Cl, 16.5-24.6) in the bevacizumab arm. ORR was 32% (95% Cl, 23%-43%) in the panitumumab arm and 19% (95% Cl, 11%-29%) in the bevacizumab arm. Skin disorders, diarrhea, hypomagnesemia, hypokalemia, dehydration, and hypotension were more frequent in the panitumumab arm. Neutropenia was more frequent in the bevacizumab-containing arm. Conclusion: Panitumumab or bevacizumab with FOLFIRI as second-line treatment had efficacy similar in patients whose disease progressed during oxaliplatin-based chemotherapy with bevacizumab, with expected toxicities. The development of more accurate biomarkers might help caregivers and patients to better choose between therapies for individual patients.