Nasopharyngeal carcinoma survivors are at excess risk of cancers of the head and neck, lung, and non-Hodgkin's lymphoma: Evidence from the SEER database. Free

A25

Background: Survival rates for nasopharyngeal carcinoma (NPC) have increased greatly in recent years, making the potential problem of second primary tumors (SPTs) in these patients more important. Few studies have looked at SPTs associated with NPC, which is quite rare in most of the world. Previous studies have all been done in Asia using cohorts of between 750 and 1600 NPC survivors and have obtained inconsistent results, probably due to lack of power. Methods: A retrospective cohort study was done using data on NPC patients from the U.S. National Cancer Institutes SEER public use data set. Standardized Incidence Ratios (SIRs) for cancer incidence after NPC were estimated overall, and stratified by site of SPT, gender, and race (White and Asian/PI). Approximate or exact Poisson confidence intervals (95%) for the SIRs were calculated as appropriate. Results: Data was available on a total of 4650 NPC patients, including 2411 Whites, 1781 Asian/Pacific Islanders, 425 blacks, and 33 Native Americans. Males outnumbered females by about 3 to 1. Statistically significant excess cancer risks were found for all sites (SIR = 1.40, 95% CI = 1.26-1.56), cancers of the lung (SIR = 2.45, 95% CI = 1.98-3.00), head and neck (SIR = 3.59, 95% CI = 2.52-4.94), and esophagus (SIR = 3.75, 95% CI = 1.87-6.72), and non-Hodgkin's lymphoma (SIR = 2.33, 95% CI = 1.42-3.60). Patterns of excess risk stratified by race and gender were generally similar except that Asians did not show excess NHL risk. Discussion: We found strong evidence of an excess risk of second cancers among NPC survivors. Whether this excess is due to treatment effects, or shared environmental or genetic factors remains to be determined. Further studies in countries with populations at high risk of NPC need to be conducted.