Simultaneous Reduction of Volume and Dose in Clinical Target Volume for Nasopharyngeal Cancer Patients.

ABSTRACT

PURPOSE: To compare the treatment outcome and severe late adverse effects (AEs) between conventional volume and dose (CVD) and simultaneously reduced volume and dose (SRVD) of clinical target volume treatments in patients with nasopharyngeal carcinoma. METHODS AND MATERIALS This retrospective cohort study enrolled patients with nonmetastatic stage II to IV nasopharyngeal cancer from a single institute. Survival endpoints and severe (≥grade 3) late AEs and comorbidity were compared between groups. The correlation of severe late AEs, comorbidity, and overall survival (OS) were evaluated using Kaplan-Meier and Cox regression methods. RESULTS: From January 2012 to June 2017, this study enrolled 178 patients, 64 in the CVD group and 114 in the SRVD group. The 2 groups did not differ significantly in patient characteristics except for mean follow-up time (37.6 vs 48.8 months; P = .01). The SRVD group did not significantly differ from the CVD group in local control survival (82.0% vs 78.4%; P = .85), regional control survival (89.9% vs 86.0%; P = .62), or disease-free survival (76.4% vs 66.9%; P = .67). The SRVD group had significantly better OS (93.9% vs 67.0%; P < .001) and salvage survival (79.3% vs 20.7%; P < .01) and a significantly lower ratio of severe lung infection (1 of 113 vs 5 of 59; P = .02). The SRVD group had a significantly lower risk of mortality (hazard ratio [HR], 0.3; P = .03). The factors associated with a significantly higher risk of mortality were N3 (regional lymph node stage status of N3) (HR, 3.0; P = .02); comorbidities of diabetes, coronary artery disease, or chronic kidney disease (grades 2-3) (HR, 3.8; P = .009), and severe lung infection (HR, 6.3; P = .007). CONCLUSIONS: Simultaneously reduced volume and dose of clinical target volumes did not impair locoregional control or disease-free survival. The benefits of SRVD treatment may include significant reduction in severe late AEs, particularly lung infection, dysphagia, and xerostomia. However, additional studies with longer patient follow-up are required to confirm these benefits.