Dosimetric Determinants of Locoregional Failure in Nasopharyngeal Carcinoma Treated with Definitive Intensity-modulated Radiotherapy (IMRT) with or without Concomitant Chemotherapy.

PURPOSE: Nasopharyngeal carcinoma (NPC) is a significant head and neck malignancy with rising incidence globally. Despite recent advances in the treatment of NPC, particularly introduction of intensity-modulated radiotherapy (IMRT) in its management, locoregional recurrence remains a major challenge, impacting patient survival and quality of life. This study evaluates the five-year locoregional failure rates and recurrence patterns in NPC patients treated with IMRT with or without Concomitant Chemotherapy.

METHODS: A historical cohort of 65 NPC patients treated at Shohadai-e-Tajrish Hospital in Tehran, Iran, from 2017 to 2019, was analyzed. All patients received definitive IMRT, with a median follow-up of five years. Recurrence patterns were classified as in-field, marginal or out-field recurrences, based on dosimetric parameters. Statistical analyses assessed recurrence associations with clinical and dosimetric factors at the significant level of p<0.05.

RESULTS: Of the 61 patients, 31.2% experienced recurrence including 18.03% with locoregional failure and 13.1% with distant metastasis. Among locoregional recurrences, 60% were in-field, 30% marginal, and 10% out-field. Mean dosimetric values for high-risk, intermediate-risk, and low-risk clinical target volumes were 68.3 Gy, 58.65 Gy, and 51.66 Gy, respectively.

CONCLUSION: Locoregional failures in NPC remain a significant clinical issue, with in-field recurrences being the most common. Strategies like dose escalation, functional imaging-guided radiation, and improved clinical target volume delineation are essential to enhance treatment outcomes and reduce recurrence rates. Further research into individualized treatment approaches and long-term toxicity data is needed to optimize patient care.