Patterns of failure after the reduced volume approach for elective nodal irradiation in nasopharyngeal carcinoma

Abstract

Purpose: To evaluate the patterns of nodal failure after radiotherapy (RT) with the reduced volume approach for elective neck nodal irradiation (ENI) in nasopharyngeal carcinoma (NPC).

Materials and methods: Fifty-six NPC patients who underwent definitive chemoradiotherapy with the reduced volume approach for ENI were reviewed. The ENI included retropharyngeal and level II lymph nodes, and only encompassed the echelon inferior to the involved level to eliminate the entire neck irradiation. Patients received either moderate hypofractionated intensity-modulated RT for a total of 72.6 Gy (49.5 Gy to elective nodal areas) or a conventional fractionated three-dimensional conformal RT for a total of 68.4-72 Gy (39.6-45 Gy to elective nodal areas). Patterns of failure, locoregional control, and survival were analyzed.

Results: The median follow-up was 38 months (range, 3 to 80 months). The out-of-field nodal failure when omitting ENI was none. Three patients developed neck recurrences (one in-field recurrence in the 72.6 Gy irradiated nodal area and two in the elective irradiated region of 39.6 Gy). Overall disease failure at any site developed in 11 patients (19.6%). Among these, there were six local failures (10.7%), three regional failures (5.4%), and five distant metastases (8.9%). The 3-year locoregional control rate was 87.1%, and the distant failure-free rate was 90.4%; disease-free survival and overall survival at 3 years was 80% and 86.8%, respectively.

Conclusion: No patient developed nodal failure in the omitted ENI site. Our investigation has demonstrated that the reduced volume approach for ENI appears to be a safe treatment approach in NPC.

Keywords: Lymphatic Irradiation; Nasopharyngeal carcinoma; Treatment failure.

Fig. 1. An example of the tailored elective neck nodal irradiation (ENI) for a patient with cT3N1 nasopharyngeal carcinoma. The beam's-eye-view display with a digitally reconstructed radiograph shows the clinical target volume (red) including an electively irradiated nodal area for a dose of 4,950 cGy. The green shows the cricoid cartilage. On the side without nodal involvement (except retropharyngeal node), ENI included only RPN, levels II, III, and Va. ENI did not routinely include the level I region.

Fig. 2. Patterns of failure.

Fig. 3. Kaplan-Meier curves of (A) locoregional control, (B) 3-year distant failure-free, (C) 3-year overall survival, and (D) 3-year disease-free survival rates.