Simultaneous reduction of volume and dose in clinical target volume for nasopharyngeal cancer patients.

PURPOSE To compare the treatment outcome and severe late adverse effects (AE) between conventional (CVD) and simultaneously reduced volume and dose of clinical target volumes (SRVD) treatments in nasopharyngeal carcinoma (NPC) patients. METHODS AND MATERIALS This retrospective cohort study enrolled non-metastatic stage II to IV NPC patients from a single institute. Survival endpoints and severe (≥G3) late AEs and comorbidity were compared between groups. The correlation of severe late AEs, comorbidity and overall survival (OS) were evaluated by 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 two groups did not differ significantly in patient characteristics except for mean follow-up time (37.6 vs. 48.8 months, p=0.014). The SRVD group did not significantly differ from the CVD group in local control survival (82.0% vs. 78.4%, p=0.852), regional control survival (89.9% vs. 86.0%, p=0.615) or disease-free survival (76.4% vs. 66.9%, p=0.665). The SRVD group had significantly better OS (93.9% vs. 67.0%, p<0.001), salvage survival (79.3% vs. 20.7%, p<0.01) and a significantly lower ratio of severe lung infection (1/113 vs. 5/59, p=0.02). The SRVD group had a significant lower risk of mortality (HR=0.3, p=0.034). The factors associated with a significant higher risk of mortality were N3 (HR=3.0, p=0.018), comorbidities of diabetes, coronary artery disease or chronic kidney disease (G2-3) (HR=3.8, p=0.009) and severe lung infection (p=0.007, HR=6.3). CONCLUSIONS Simultaneously reduced volume and dose of CTVs did not impair loco-regional 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.