Radiotherapy With Weekly Cetuximab Versus Triweekly Carboplatin In The Definitive Treatment Of Cisplatin-Ineligible Patients With HPV-Associated Oropharyngeal Squamous Cell Carcinoma: One Institution’s Retrospective Experience

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Although Triweekly Cisplatin-based concurrent chemoradiation has recently been shown to be superior to Cetuximab-based concurrent therapy in HPV-associated oropharyngeal squamous cell carcinoma (OPSCC) in multiple randomized trials, the optimal concurrent agent in those who are poor candidates for Cisplatin is unknown. Here we report the cancer control and survival outcomes in this cohort of patients who underwent radiotherapy concurrent with either triweekly Carboplatin or weekly Cetuximab at our institution. A retrospective review was conducted from November 2006 through September 2016 of patients with non-metastatic p16-positive OPSCC who underwent definitive intensity modulated radiotherapy to a median dose of 70 Gy (range 66-70 Gy) concurrent with weekly Cetuximab (n = 40) per Bonner protocol or triweekly Carboplatin (AUC = 5) (n = 191). No patient received accelerated radiotherapy. Patients receiving induction chemotherapy or oncological surgery of any kind prior to concurrent therapy were excluded. All patients had stage conversion according to the AJCC 8th Edition Cancer Staging Manual. Three-year locoregional recurrence (LRR), distant metastasis (DM), overall recurrence rate (ORR), overall survival (OS), and cause-specific survival (CSS) are reported. Cetuximab and Carboplatin groups were compared accounting for age, sex, smoking history, T stage, and N stage. Patients who received Carboplatin were younger (median age 62 vs. 70, P<0.001). The Cetuximab group had a higher percentage of patients with >10 pack-years of smoking (57% vs. 37%, P<0.02). The two cohorts were otherwise well-balanced with respect to other baseline patient and disease characteristics including T and N stage. After a median follow up of 40 months for surviving patients, those receiving Carboplatin had lower 3-year rates of LRR (8% vs. 16%, p = 0.02), DM (11% vs. 21%, p = 0.01), and ORR (17% vs. 29%,p = 0.008), and superior OS (90% vs. 63%, p = 0.003) and CSS (93% vs. 77%, p = 0.01). Our study suggests that, if medically feasible, triweekly Carboplatin concurrent with radiotherapy should be preferred to that with cetuximab in patients with p16+ OPSCC who are not eligible to receive cisplatin as it results in superior cancer control and survival outcomes.