Delineation of the Clinical Target Volume in Early-Stage Nasopharyngeal Carcinoma Treated With Intensity Modulated Radiation Therapy: Long-Term Follow-Up of a Phase 2 Study

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.

Feasibility of a Skin Dose Reduction for Nasopharyngeal Carcinoma Treated With High-Intensity-Modulated Delivery Techniques

Acute skin toxicity observed in radiotherapy treatment of head and neck cancer is a big concern. The purpose of this work is to evaluate the feasibility of a skin dose reduction in the treatment of nasopharyngeal carcinoma without compromising the overall plan quality. This research focused on comparison of the skin dose reduction that can be obtained for the main high conformal radiotherapy delivery techniques. Sixteen cases of early-stage nasopharyngeal carcinoma were included in this study. For each case, a dynamic intensity-modulated radiation therapy, a volumetric modulated arc therapy, and a helical tomotherapy treatment plans were performed with and without the skin as a sensitive structure in the inverse plan optimization. The dosimetric results obtained for the different treatment techniques and plan optimizations were compared. Dose–volume histogram cutoff points of D95%, D98%, and the homogeneity index were used for target comparison, while Dmean and Dmax/D1cc were used for the organs at risk. The skin volume receiving 5 Gy and then 10 to 70 Gy of radiation dosage registered at step of 10 Gy and Dmean were used for the skin dose comparison. One-way analysis of variance was used to assess the dosimetric results obtained for the different types of treatment plans and techniques investigated. A total of 96 treatment plans were analyzed. When the neck skin was considered in the treatment optimization process, the skin volume that received more than 30 Gy was reduced by 3.7% for dynamic intensity modulated, 4.1% for volumetric modulated arc, and 4.3% for dynamic intensity modulated, while the target dose coverage and organs at risk dosages remained unvaried (p > .05).