Purpose The evidence associating cancer risk with diagnostic radiation exposure is unclear. Men recovering from low-grade testicular cancer frequently undergo serial abdominal-pelvic computerized tomography (CT) scanning to monitor for recurrent disease. Methods We used population-based administrative data sets to identify every incident case of testicular cancer between 1991 and 2004 in Ontario, Canada. We excluded those with previous cancer, concurrent radiation therapy, retroperitoneal lymph node dissection, or fewer than 5 years observation. Patients were observed until the occurrences of death or development of a second abdominal-pelvic malignancy or until December 31, 2009. Results A total of 2,569 men (mean age, 34.7 years; standard deviation, 10.2) were observed for a median of 11.2 years (interquartile range [IQR], 8.3 to 14.3). During the first 5 years after diagnosis, men underwent a median of 10 computed tomography (CT) scans (IQR, 4 to 18) of the abdominal-pelvic area, and they were exposed to a median of 110 mSv of radiation from radiologic investigations (IQR, 44 to 190). After this, 14 men were diagnosed with a second abdominal-pelvic malignancy (rate, five per 10,000 patient-years observation, 95% CI, three to eight); the most common diagnoses were colorectal and kidney malignancies. Radiation exposure was not associated with an excess risk of second cancers (hazard ratio per 10 mSv increase, 0.99; 95% CI, 0.95 to 1.04). This association did not change if men observed for fewer than 5 years were included in the analysis (hazard ratio, 1.00; 95% CI, 0.96 to 1.04). Conclusion Second malignancies of the abdomen-pelvis are uncommon in men with low-grade testicular cancer. In this study, the risk of second cancer was not associated with the amount of diagnostic radiation exposure.
[P155] Exposure levels from CT scanning for treatment planning in radiotherapy