Long-term outcomes in patients with nasopharyngeal carcinoma treated with reduced-volume conformal radiotherapy: A retrospective cohort study

Introduction: While the optimal target volumes for primary nasopharyngeal tumour are still subject to debate, we evaluated primary tumour volumes in nasopharyngeal carcinoma (NPC) patients treated according to an institutional protocol with a reduced volume approach and compared them to those determined by Radiation Therapy Oncology Group (RTOG)-0615 guidelines. Methods: This single-centre retrospective analysis included 36 NPC patients treated between 2/2007 and 3/2014. Planning target volume (PTV)-P 50 (50 Gy isodose to the primary tumour) included the gross tumour and the entire nasopharyngeal mucosa (clinical target volume [CTV]–P 50) with 5 mm margins. The PTV-P 50 volumes, as determined by our protocol, were compared to those obtained with RTOG-0615 PTV-P 59.4 (59.4 Gy to the primary tumour). Clinical outcomes were also analysed. Results: Median (range) follow-up: 48 (21–108) months; 88.9% were males; median age was 53 (27–86) years; 14%, 53%, and 33% had stage II, III, and IV disease at diagnosis, respectively. Median volume of PTV-P 50: 209.0 (92.6–568.0) cc. Median volume of RTOG-0615 PTV-P 59.4-P: 292.0 (123.6–425.1) cc. The PTV-P volume was significantly smaller than that delineated according to the RTOG-0615 protocol (p < 0.001). Isolated local relapse as first site of recurrence occurred in five patients: two with stage III, two with IVA and one with IVB disease; all had advanced local disease at diagnosis. All local recurrences occurred in the PTV-P 69-70 region. Conclusion: A reduced volume approach for radiotherapy in primary NPC provided acceptable long-term local control.