De-escalation treatment of patients with HPV-positive oropharyngeal squamous cell carcinoma.

e18052 Background: According to Globocan in 2020 were identified 98 412 new cases of oropharyngeal squamous cell carcinoma in the world. It was proved that the human papillomavirus (HPV) is a favorable prognostic factor. Patients with HPV-positive oropharynx cancer have higher indicators of progression-free survival (PFS) and overall survival (OS). As induction chemotherapy, the only TPF regimen (cisplatin/ docetaxel/ 5-fluorouracil) has been approved which has high toxic profile. Published results of randomized trials demonstrate the possibility of de-escalation CRT without reduction OS and PFS, but there is no data about safety of de-escalated IC regimen. Given the high toxicity of the standard regimen, as well as the presence of a favorable prognostic factor (HPV infection), since 2021 has started a prospective trial, investigating the possibility of use the dual-component IC regimen according to the TP scheme (cisplatin/ docetaxel). Objective: Improve the results of treatment of patients with locally advanced HPV- positive squamous cell carcinoma of the oropharynx by optimizing the scheme IC. Methods: In the prospective trial included 68 patients with p16-positive oropharyngeal squamous cell carcinoma (T3-4N0-1M0, or T1-4N2-3M0), who were divided into 2 equal groups. The research group received 3 cycles of IC to the de-escalated TP regimen and the control group according to the standard three-component TPF regimen. After completion IC patients of both groups had a standard CRT 70 Gy with carboplatin AUC 2.0 weekly. The primary endpoints were the assessment of objective response rate after the IC and toxicity. The Secondary endpoints: 1-year OS and PFS. Results: Complete response (CR) was achieved in 3 patients (8,8%), a partial response (PR) in 22 (64,7%), stable disease (SD) in 8 (23,5%) patients in the research arm. In the control arm: CR 4 patients (11,8%), PR 24 (70,6%), SD 6 (17,6%) patients. Both IC regimens demonstrated high efficacy rates, and there was no statistically significant ORR in the group (p=0,2133).Toxic manifestations were often observed in the arm of standard IC. The higher incidence of mucositis in the control group was statistically significant (p=0,025). The effect of IC regimen on subsequent CRT was also assessed. In the research arm, the time before the start of CRT was statistically significantly less than in the control arm (30 days vs 63 days, p=0,0035.). And the period of development mucositis of CRT in the TP group was longer than in the TPF group (34G vs 32G, p=0,0298). 1 year - PFS 94%, 1 year - OS 100% in the research group and 92% and 100% in the control arm. There was no statistically significant 1 year – PFS and 1 year - OS in the group (р=0,6547). Conclusions: The research scheme of IC demonstrated high results of an objective response, 1-year OS and 1 year - PFS, comparable to the standard TPF scheme, against the background of better tolerance.