Dr Rischin on the Safety of Adjuvant Cemiplimab in High-Risk CSCC

“This is the first trial to show in a clinically meaningful and statistically significant way that an adjuvant therapy, in this case, adjuvant cemiplimab, can improve the outcome for these patients with advanced disease, and this represents a new potential standard-of-care option for both patients and their oncologists to consider.”

Danny Rischin, MD, professor and director of Medical Oncology at the Peter MacCallum Cancer Centre, discussed the safety profile of adjuvant cemiplimab-rwlc (Libtayo) in patients with high-risk cutaneous squamous cell carcinoma (CSCC). During the randomized phase 3 C-POST trial (NCT03969004), investigators evaluated the tolerability of cemiplimab compared with placebo following surgery in this patient population. The duration of exposure was similar between the 2 arms, with a median of approximately 48 weeks.

Findings showed that treatment-emergent adverse effects (TEAEs) of any grade occurred in 91% of patients who received cemiplimab (n = 205) and in 89% of those who received placebo (n = 204). Grade 3 or higher TEAEs were observed more frequently with cemiplimab (24%) compared with placebo (14%). Any-grade serious TEAEs were reported in 18% of patients in the cemiplimab arm vs 9% of those in the placebo arm. Treatment discontinuations due to any-grade TEAEs occurred in 10% of patients receiving cemiplimab and 1% of those receiving placebo. Fatal TEAEs of any grade occurred in 1% of patients in each arm.

Treatment-related TEAEs were observed in 62% of cemiplimab-treated patients, including 10% of patients with grade 3 or higher effects, compared with 46% and less than 1% of patients, respectively, in the placebo group. Immune-mediated AEs were more common in the cemiplimab arm (23% any grade; 7% grade ≥ 3) than in the placebo arm (6% any grade; 0% grade ≥ 3). The most frequent any-grade TEAEs occurring in at least 10% of patients included fatigue (22% in both arms), pruritus (cemiplimab arm, 16%; placebo arm, 12%), rash (16%; 9%), diarrhea (16%; 19%), arthralgia (13%; 12%), hypothyroidism (12%; 3%), and maculopapular rash (11%; 6%). Most effects were low grade.

Rischin emphasized that the safety profile of adjuvant cemiplimab was consistent with what has been observed with other anti–PD-1 monotherapies and with cemiplimab in the advanced setting. No unexpected toxicities were reported, and treatment was generally well tolerated. Importantly, he noted that this trial represents the first to demonstrate in a statistically significant and clinically meaningful manner that adjuvant cemiplimab can improve outcomes in patients with high-risk CSCC following surgery.

Rischin concluded that these findings support adjuvant cemiplimab as a potential new standard-of-care option for this population, offering patients and oncologists an evidence-based approach to reducing recurrence risk without introducing new safety concerns.