Risk factors for primary site necrosis after definitive concurrent chemoradiotherapy in head and neck cancer

Objective: To identify risk factors of primary site necrosis (PSN) after definitive concurrent chemoradiation therapy (CCRT) in patients with nonoral cavity head and neck cancer (HNC). Methods: We retrospectively reviewed the records of 256 patients treated with CCRT for HNC during 2010–2018. Patient-related (age, sex, history of smoking, hypertension, diabetes mellitus, serum hemoglobin and albumin), tumor-related (tumor site, American Joint Committee on Cancer stage), and treatment-related (induction chemotherapy, maximum point dose and mean dose of planning target volume [PTV] of primary site, absolute volumes of the PTV receiving >50–75 Gy [V50–V75]) variables were analyzed. Critical dosimetric parameters of PSN were identified using receiver operating characteristic (ROC) curve analysis. Univariate and multivariate Cox regression analyses were used to select the significant variables for PSN development. Results: After median follow-up of 44 months (range, 5–127), 7 patients (2.7%) developed PSN with a median time to event of 10 months (range, 3–12). V70 ⩾79.8 mL was the most critical dosimetric parameter for PSN (area under the ROC curve 0.873, sensitivity 0.857, specificity 0.747). In univariate analyses, pretreatment serum hemoglobin <11.0 g/dL and V70 ⩾79.8 mL were significantly associated with higher risk of PSN occurrence. V70 ⩾79.8 mL (hazard ratio 5.960, 95% confidence interval 1.289–27.548; p = 0.022) remained significant predictors of PSN in multivariate analyses. Conclusions: V70 ⩾79.8 mL is significantly related to the risk of developing PSN. These findings offer valuable clues for clinicians to minimize PSN incidence in HNC treated with curative CCRT.