Session Item

Human papillomavirus (HPV)-associated tonsillar cancer has a better prognosis than HPV-negative cancer, so deintensification strategies to reduce or exclude radiotherapy (RT) have been suggested through several studies. However, there is no strong evidence or guidelines for deintensification of RT. In this study, we investigated the treatment outcome in patients with HPV-associated tonsillar cancer and provide deintensification strategy for RT.

Retrospective cohort study of patients with clinical stage T1-4N0-3 HPV-associated tonsillar cancer treated between 2008 and 2020 with primary surgery or RT. Overall survival (OS), progression-free survival (PFS) and cumulative incidence of locoregional failure (LRF) between primary surgery and primary RT were analyzed, and propensity score matching was performed to adjust for clinical factors. The following subgroup analysis was conducted for patients who received primary surgery; The difference in LRF according to adjuvant RT, prognosis differences according to pathological response after neoadjuvant chemotherapy, and risk factors related to contralateral regional failure in initial contralateral neck lymph node (LN)-negative patients.

Of the total patients, 84 patients (22.5%) received primary surgery alone, 224 patients (59.9%) received primary surgery plus adjuvant RT, and 66 patients (17.6%) received primary RT. After adjusting for clinical factors, there was no statistical difference in OS, PFS, and LRF between the primary surgery group and the primary RT group. In subgroup analysis, advanced pathologic N stage, contralateral LN metastasis at diagnosis, abutting or positive surgical resection margin, and no adjuvant RT were independent risk factors of LRF in patients undergoing primary surgery. There was no locoregional failure or death among 22 patients who had received neoadjuvant chemotherapy before surgery and achieved pathological complete remission. Among them, 15 patients (68.2%) did not receive adjuvant RT. Among 282 initial contralateral neck LN-negative patients who underwent primary surgery, 8 patients had contralateral regional failure. None of these patients underwent contralateral neck dissection, and all resection margins were less than 1 mm or positive. In multivariate analysis, lymphovascular invasion and elective contralateral neck irradiation not higher than 30.6 Gy were independent risk factors of contralateral regional failure.

In patients undergoing primary surgery, adjuvant RT can reduce LRF, and can be further considered, especially for advanced N stage or abutting or positive resection margin. Contralateral regional failure occurred in only 2.8% of initial contralateral neck LN-negative patients who underwent primary surgery. However, for patients who have adverse features such as lymphovascular invasion and close resection margin and have not undergone contralateral neck dissection, elective contralateral neck irradiation with a dose higher than 30.6 Gy can be considered.