Proton beam therapy for locally advanced and unresectable (T4bN0M0) squamous cell carcinoma of the ethmoid sinus: A report of seven cases and a literature review

The present study reports treatment outcomes of locally advanced and unresectable squamous cell carcinoma of the ethmoid sinus (SCC-ES) following proton beam therapy (PBT). Between January 1997 and December 2012, 7 patients (median age, 63 years) with SCC-ES underwent definitive PBT. All tumors were categorized as T4bN0M0 (2009 UICC tumor-node-metastasis classification) and were treated using conventional fractionation at a median total dose of 72 Gy equivalents (GyE; range, 70.4-76 GyE). Imaging diagnosis for the initial treatment effect within 3 months of PBT revealed that a complete response (CR) was achieved in 2 patients and a partial response (PR) in 5 patients. The overall median survival time of the patients was 43 months (range, 12-62 months), and 4 patients survived for ≥3 years. No recurrence was observed in the 2 patients who exhibited an initial CR treatment effect; however, locoregional recurrences occurred in 4/5 patients who exhibited a PR. No grade 3 or severe acute toxicities were observed, but the late toxicities of grade 3 contralateral optic nerve damage and cataracts developed in 1 and 2 patients, respectively. Based on the findings of the present study, intensification of the local treatment effect may be important for yielding favorable treatment outcomes, since no distant metastasis was observed. PBT is therefore a potentially useful treatment tool for unresectable SCC-ES.