The Clinical Characteristics of Secondary Primary Tumors in Patients With Nasopharyngeal Carcinoma after Intensity-Modulated Radiation Therapy: A Retrospective Analysis

Abstract

To investigate the clinical characteristics associated with the risks of developing a secondary primary tumors (SPTs) in patients with nasopharyngeal carcinoma (NPC) who underwent intensity-modulated radiotherapy (IMRT). Data from 527 patients with biopsy-proven non-metastatic NPC, who were treated with IMRT between January 2007 and December 2011, were analyzed retrospectively. The cumulative incidence of SPTs after IMRT completion was estimated using the Kaplan–Meier method. Differences in cumulative incidence between groups were determined using the log-rank test. The median follow-up time was 45.5 months (range, 4–97 months). Of 527 patients, 12 (2.3%) developed posttreatment SPTs (9 men and 3 women), 6 of which were located in the irradiated field. SPTs were mostly located in the upper aerodigestive tract (n = 7), the head and neck (n = 6), the lungs (n = 3), and the tongue (n = 2). The 1-, 3-, and 5-year cumulative SPT risk rates were 0.4%, 1.4%, and 3.1%, respectively, and the mean annual growth of cumulative incidence was ∼0.6%. The 1-, 3-, and 5-year cumulative in-field SPT risk rates were 0.4%, 0.8% and 1.5%, respectively, and the mean annual growth of in-field cumulative incidence was ∼0.3%. Univariate analysis revealed that sex, age, clinical stage, administration of chemotherapy, and overall IMRT duration did not significantly affect SPT risk. The 5-year SPTs incidence in the NPC patients after IMRT is concordant with or lower than that in previous 2D-RT studies .In patients with NPC who underwent IMRT, the upper aerodigestive tract was the most common site of SPTs, with lung cancer being the most common pathology. Further large-scale studies with longer-term follow-up are needed to determine risk factors associated with SPTs development after IMRT.