Impact of clinical complete response on treatment outcomes in patients with locally advanced HPV-negative oropharyngeal squamous cell carcinoma

Objective To evaluate treatment outcomes after definitive chemoradiotherapy (CRT) for human papilloma virus (HPV)-negative oropharyngeal squamous cell carcinoma (OPSCC). Materials and methods We analyzed data concerning HPV-negative OPSCC patients treated with curative intent. All patients received concomitant high-dose cisplatin-based chemotherapy. Two different RT techniques were used: (1) sequential boost IMRT (S-IMRT) to a total dose of 70 Gy (2 Gy/fraction); (2) simultaneously integrated boost (SIB-IMRT) to a total dose of 67.5 Gy (2.25 Gy/fraction). Survival outcomes were estimated. Results In total, 69 HPV-negative OPSCC patients were included (n = 40 S-IMRT; n = 29 SIB-IMRT). The median follow-up time was 40 months. The 3-year overall survival, disease-free survival, distant metastasis-free survival and locoregional-free survival were 67.1%, 63.3%, 64.5% and 66.0%, respectively. Alcohol abuse and advanced stage disease at presentation were the main risk factors for worse survival outcomes. Complete clinical response (cCR) at 3 months after CRT improved overall survival (86.3% versus 42.5%, p < 0.01). The cCR events were greater but not statistically significant in SIB-IMRT group compared to S-IMRT patients (69% versus 47.5%, p = 0.09). Conclusions The positive impact of cCR at 3 months on survival needs to be confirmed in randomized clinical trials, as well as its close correlation with SIB-IMRT technique. A proper stratification of HPV-negative OPSCC patients should be paramount to tailor treatment strategy in the near future.