Advanced penile squamous cell carcinoma is a rare disease with a 21% 2-year overall survival (OS) rate.
The single-center, nonrandomized, phase 2 PERICLES study assessed the activity of atezolizumab, an anti-PD-L1, with and without radiotherapy (RT) to determine which approach is more effective in patients with advanced penile cancer.
The study’s primary end point was 1-year progression-free survival (PFS) for the full cohort, which was reached if the actual 1-year PFS was at least 35%. Secondary end points included OS, objective response rate (ORR), and tolerability.
A total of 31 patients with advanced penile cancer were included in the study. Each patient received atezolizumab 1200 mg once every 3 weeks, and 20 patients received additional irradiation. The median follow-up was 29.1 months.
Grade 3 and 4 adverse events occurred in 3 (9.4%) patients in the atezolizumab monotherapy arm and 13 (65%) patients in the RT arm. The primary end point was not met, as the one-year PFS rate was 12.5% (95% CI, 5.5-18.7). Median OS was 11.3 months (95% CI, 5.5-18.7). In the objective response-evaluable population (n=30; 93.8%), the ORR was 16.7% (95% CI, 6-35), including 2 (6.7%) complete responders and 3 (10%) partial responders.
Improved PFS was noted in patients with high-risk human papillomavirus-positive tumors (P=.003) and in patients with high infiltration of intratumoral CD3+CD8+ T cells (P=.037).
While the study’s primary end point was not met, antitumor activity from atezolizumab was seen in a subset of patients.