Impact of primary tumor-specific growth rate on treatment failure for nonoropharyngeal head and neck cancers

Objectives: To investigate the prognostic impact of primary tumor-specific growth rate (TSGR) on treatment outcomes after definitive radiation therapy (RT) for nonoropharyngeal squamous cell carcinoma (non-OPSCC). Methods: The diagnostic tumor and nodal volumes of 39 non-OPSCC patients were contoured and compared to corresponding RT planning scan volumes to determine TSGR. Overall survival (OS), disease-free survival (DFS), and local recurrence-free survival were evaluated according to the Kaplan-Meier method; and hazard ratios (HR) were estimated using Cox regression. Based on the 75th percentile TSGR of 2.18%, we stratified patients into a high TSGR group (≥ 2.18% per day) and low TSGR group (< 2.18% per day). Results: The median follow-up was 22 months (range: 1–86 months) and median time between diagnostic and simulation computed tomography scans was 22 days (range: 7–170 days). Median RT dose was 70 Gy (range: 60–79.2 Gy). Based on the 75th percentile TSGR, OS at median follow-up was 50.0% for the high TSGR group compared to 92.5% for the low TSGR group (HR [95% confidence interval (CI)] = 2.12[1.16–11.42], P = 0.018). There was a trend toward worse DFS at median follow-up for the high versus low TSGR groups, at 55.6% and 82.3%, respectively (HR [95% CI] = 2.29[0.82–6.38], P = 0.103). Conclusion: Our study contributes to growing literature on TSGR as a temporal biomarker in patients with non-OPSCC. Patients with high TSGR ≥2.18% per day have significantly worse OS compared to those with TSGR below this threshold. Efforts to address treatment initiation delays may benefit patients with particularly aggressive and rapidly growing tumors. Level of Evidence: 4 Laryngoscope, 130:2378–2384, 2020.