Retrospective Analysis of Efficacy and Toxicity of Low-Dose Weekly Cisplatin Concurrently with Radiotherapy for p16-Positive Oropharyngeal Squamous Cell Carcinoma

Background: The incidence of p16-positive oropharyngeal squamous cell carcinoma (OPSCC) is increasing, with improved prognosis compared to non-HPV-related cancers. Standard treatment of locally advanced OPSCC involves high-dose cisplatin (HDC) with radiation but is associated with significant toxicity. Low-dose cisplatin (LDC) administered weekly has shown comparable efficacy to HDC in prior studies. This study evaluates the real-world outcomes of LDC in p16-positive OPSCC in a regional centre. Material and methods: Patients treated with curative radiation and concurrent LDC (40 mg/m2 weekly) for p16-positive OPSCC from January 2015 to December 2021 were retrospectively analysed (n = 103). Primary endpoints included overall survival (OS) and progression-free survival (PFS), with secondary endpoints being loco-regional and distant recurrence rates, and chemotherapy-related toxicity. Results: Overall survival rates were 94%, 89%, and 84% at two, three, and five years, respectively. The progression-free survival rates were 90%, 83%, and 80% over the same periods. The low-risk group showed excellent outcomes with no loco-regional recurrences and low distant relapse rates (6% at 5 years). The intermediate-risk group had higher loco-regional recurrences (10% at 5 years) and a similar distant relapse rate (7% at 5 years). T4 or N3 disease patients had lower survival and higher distant relapse rates but excellent loco-regional control. The median cumulative cisplatin dose was 240 mg/m2, with no survival difference between those receiving ≥200 mg/m2 versus less. Toxicity led to dose reductions (8%), delays (13%), and early cessations (30%). Conclusions: LDC is effective for p16-positive OPSCC with manageable toxicity, showing outcomes comparable to outcomes previously reported in studies using HDC.