A Report of Delayed Toxicities of Intensity Modulated Radiation Therapy for Nasopharyngeal Carcinoma: A Single Center Cross-sectional Study

Background: Based on the literature review, the available information regarding late toxicities after intensity modulated radiation therapy (IMRT) for nasopharyngeal carcinoma (NPC) is limited to a few countries. Objectives: This study provides an opportunity to evaluate the delayed toxicities among Iranian patients with NPC that underwent IMRT. Methods: Between February 2016 and September 2018, 32 patients were treated with IMRT for NPC at Shohada-e Tajrish Hospital. The majority of them were in the advanced clinical stage and all received platinum-based induction and/or concurrent chemotherapy. Our typical prescription dose was 70.2 Gy to the gross tumor volume (GTV) in 2 Gy per fraction. Uninvolved regional lymph nodes received 59.4 Gy. Considering the minimum follow-up time of 6 months, we aimed mainly at evaluating the rate of delayed toxicities, including xerostomia, hearing loss, and eyeball damages. Toxicities were categorized based on either RTOG/EORTC or LENT/SOMA criteria. Results: The median follow-up time was 12 months (6 - 32 months). The occurrence rates of grade ≥ 2 xerostomia, grade ≥ 2 hearing loss, optic neuropathy, and retinopathy were 28%, 10%, 4%, and 7%, respectively. Based on the dose-volume histogram analysis, averages of mean doses to the parotid glands, submandibular glands, oral cavity, and cochlea were 32.3 Gy, 58.9 Gy, 41.8 Gy, and 44.9 Gy, respectively. Conclusions: Our experience of using IMRT in the treatment of NPC revealed equivalent toxicities (except for hearing loss) in comparison with high-experienced centers.