First results of a multicenter, non-randomized, prospective phase II study of the efficacy and safety of induction therapy with pembrolizumab, cisplatin, and 5-fluorouracil in patients with unresectable squamous cell carcinoma of the oropharynx, hypo

Background. The approved regimen of induction chemotherapy with docetaxel + cisplatin + 5-fluorouracil has high risk of unacceptable toxicity for many patients with advanced head and neck cancer (HNSCC). Toxicity can also compromise the delivery of the following chemoradiation. In order to improve the results of these pts treatment we conducted a prospective multicenter non-randomized phase II study of induction immunochemotherapy followed by (chemo)radiation and here we report first results of objective response rate (ORR), the safety profile of induction therapy and risk of further radiation therapy omission (NCT05551767). Materials and methods. The inclusion criteria were: unresectable stage III–IVA cancer of larynx, oropharynx, hypopharynx, PD-L1-positive (CPS≥1) squamous cell cancer, ECOG 0-2. Included pts received 3 cycles of pembrolizumab 200 mg d1+ cisplatin 100 mg/m2 d1 + 5-fluorouracil 1000 mg/m2/day 1-4 d followed by (chemo-) radiation. Results. Since January 2022 a total of 120 pts were included. Median age was 60 (35–75), the majority were male (105; 87.5%). Objective responses were assessed in 116 of 120 pts. ORR on induction phase was 62.9% (n=73), including 16.4% (n=19) of complete responses. Median change of target lesions was -55% (from -100% to 65%). To date, only 7 pts did not start (chemo)radiation in time due to disease progression (4 pts) or refuse of consent (3 pts). Among 95 pts who completed radiation therapy 94.7% received radiation dose ≥66Gy. The incidence of grade 3-4 adverse events was 30,8%, in 6 (5%) pts it required hospitalization. No grade 5 adverse events were observed. The most common toxicity was hematological with neutropenia grade 3-4 in 28 (23.3%) pts. There was mild immune-related toxicity: 2 (1.7%) pts had skin rash and 1 (0.8%) – hypothyroidism. The use of high dose of cisplatin resulted in a trend to decline glomerular filtration rate (median decrease was 10.5% from baseline) although none of pts required hemodialysis. Conclusion. Induction therapy with pembrolizumab plus cisplatin and 5-fluorouracil provided meaningful ORR and acceptable safety profile in locally advanced HNSCC. It almost did not influence the following radiation therapy omission rate. Further follow-up is needed to assess long-term efficacy.