Atezolizumab, given with or without radiotherapy, has demonstrated activity in a subset of patients with penile cancer, according to research published in the Journal of Clinical Oncology.
Atezolizumab did not meet the primary efficacy endpoint in the overall cohort of this phase 2 study. However, researchers did observe antitumor activity in patients with high-risk human papillomavirus (hrHPV) positivity or high intratumoral CD3+CD8+ T-cell infiltration.
This trial, PERICLES (ClinicalTrials.gov Identifier: NCT03686332), included 32 patients with stage IV penile cancer. They were treated with atezolizumab at 1200 mg every 3 weeks. Patients who were expected to benefit from radiotherapy for locoregional control also received radiotherapy (n=20).
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The patients’ median age at baseline was 67 (range, 41-78) years, and 75% of them had metastatic disease. Most patients (75%) had received previous treatment, including radiotherapy (34.4%), chemoradiation (21.9%), systemic therapy (6.2%), and surgery (68.8%).
The primary endpoint was 1-year progression-free survival (PFS) of at least 15% per the null hypothesis and 35% per the alternative hypothesis. With a median follow-up of 29.1 months, the 1-year PFS rate in the full cohort was 12.5%, which failed to meet the primary endpoint.
Similarly, the 1-year PFS rate in patients receiving atezolizumab plus radiotherapy did not meet the endpoint (10.0%; P =.36). However, in the patients treated with atezolizumab alone, the 1-year PFS rate was 16.7% (P <.001).
In an exploratory biomarker analysis, the median PFS was 5.3 months in patients with hrHPV-positive tumors and 2.6 months for patients with hrHPV-negative tumors (P =.003).
Similarly, patients with high infiltration of intratumoral CD3+CD8+ T cells had longer PFS than those with low infiltration — 5.1 months and 2.6 months, respectively (P =.037).
The objective response rate was 16.7% in the overall cohort, in the radiotherapy arm, and in the atezolizumab-alone arm. The median duration of response was not reached in the overall cohort, 6.7 months in the radiotherapy arm, and not reached in the atezolizumab-alone arm.
The median overall survival was 11.3 months in the overall cohort, 12.0 months with radiotherapy, and 8.9 months without radiotherapy.
“[A]lthough this study did not meet the primary endpoint of 1-year PFS, clinical activity of checkpoint inhibitor was observed, including durable responses in a limited number of patients,” the researchers wrote. “Our study suggests hrHPV positivity and intratumoral CD3+CD8+ T-cell infiltration as possible biomarkers to select a broader population of patients with penile cancer who are more likely to derive clinical benefit to checkpoint inhibition in future clinical trials.”
Disclosures: This research was supported by Hoffmann-La Roche. Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.
Reference
de Vries HM, Rafeal TS, Gil-Jimenez A, et al. Atezolizumab with or without radiotherapy for advanced squamous cell carcinoma of the penis (the PERICLES study): A phase II trial. J Clin Oncol. Published July 24, 2023. doi:10.1200/JCO.22.02894
