The Phase II Study of Panitumumab in ChemotherapyNaive Frail or Elderly Patients with RAS Wild-type Colorectal Cancer: OGSG 1602 Final Results

Background: We previously reported the response rate of a phase II OGSG1602 study on panitumumab in chemotherapy-naive frail or elderly patients with RAS wild-type unresectable colorectal cancer (CRC) [Terazawa T, Kato T, Goto M, et al. Oncologist. 2021;26(1):17]. Herein, we report a survival analysis. Methods: Patients aged >= 65 years and considered unsuitable for intensive chemotherapy or aged >= 76 years were enrolled. Primary tumors located from the cecum to the transverse colon were considered right-sided tumors (RSTs); those located from the splenic flexure to the rectum were considered left-sided tumors (LSTs). Results: Among the 36 enrolled patients, 34 were included in the efficacy analysis, with 26 and 8 having LSTs and RSTs, respectively. The median progression-free survival (PFS) and overall survival (OS) were 6.0 [95% CI, 5.4-10.0] and 17.5 months (95% CI, 13.8- 24.3), respectively. Although no significant differences existed in PFS between patients with LST and RST {6.6 (95% CI, 5.4-11.5) vs. 4.9 months [95% CI, 1.9-not available (NA), P =.120]}, there were significant differences in OS [19.3 (95% CI, 14.2-NA) vs.12.3 months (95% CI, 9.9-NA), P =.043]. Conclusion: Panitumumab showed favorable OS in frail or elderly patients with RAS wild-type CRC and no prior exposure to chemotherapy. Panitumumab may be optimal for patients with LSTs (UMIN Clinical Trials Registry Number UMIN000024528).

Automated summary

This study aimed to investigate the efficacy of panitumumab in patients with RAS wild-type colorectal cancer. The results showed that panitumumab demonstrated favorable overall survival in frail or elderly patients without prior exposure to chemotherapy, with a more significant effect observed in patients with left-sided tumors.