Objective To analysze the clinical characteristics of second primary tumor in nasopharyngeal carcinoma(NPC) patients after intensity-modulated radiotherapy(IMRT). Methods Clinical characteristics and follow-up of second primary tumor in 527 patients with NPC after IMRT from January 2007 to December 2011 were analyzed retrospectively. Results During a mean follow-up of 45.5 months(4.0-97.0), 12 cases developed second primary tumor, and 6 cases occurred in the radiation field. The number of second primary tumor located in lung, tongue, neck, kidney, brain, oral or stomach was,respectively, 3, 2, 2, 2,1, 1 and 1. The cumulative risk of second primary tumor were 0.4% at 1 year, 1.4% at 3 year ,and 3.1% at 5 year, while they were 0.4%, 0.8% and 1.5% respectively in the radiation field. Sex, age, clinical stage, chemotherapy and radiation duration in NPC patients with IMRT were not related with the cumulative risk of second primary tumor(P>0.05). Conclusions Upper gastrointestinal tract is the most common site of second primary cancers in NPC after IMRT treament, and the most common cancer is lung cancer.
