Background: Approximately 3-5% of patients with cutaneous squamous cell carcinoma (cSCC) develop advanced disease, accounting for roughly 1% of all cancer deaths in Australia. Pembrolizumab and cemiplimab are the current PD-1/PD-L1 inhibitors approved for the treatment of advanced cSCCs. However, current evidence in advanced cSCC is limited to several phase II clinical trials and case reports only. In this review, we describe our experience with PD-1/PD-L1 inhibitors in this patient population.
Method: We retrospectively reviewed all patients treated with immunotherapy for locally advanced and metastatic cSCC within the Illawarra and Shoalhaven Local Health District. Standard demographic, clinicopathological characteristics, treatment data using PD-1/PD-L1 inhibition, and outcomes were assessed.
Results: Among the 31 patients treated with PD-1 or PD-L1 inhibitors, there was an overall response rate of 61%, for which 22% of patients achieved a complete response (CR), and 39% achieved a partial response (PR). Our response rates are slightly higher than the 50% response rate reported in current literature, with median progression-free survival (PFS) and overall survival (OS) not reached. Interestingly, male patients were more likely to have better responses (CR + OR + SD = 90% vs 50%, p=0.011). Female patients had a significantly shorter PFS (median PFS = 3.6 months vs not reached, p=0.0008) and OS (median OS 16.1 months vs not reached, p = 0.004).
Conclusion: Treatment of advanced cSCC with PD-1/PD-L1 inhibitors results in durable responses. Our response rate of 61% is similar to that described in current literature. Our review found that male patients respond significantly better as compared to female patients. As not all patients respond to immunotherapy, further studies are needed to identify biomarkers of response.