Cumulative imaging radiation exposure following breast-conservation therapy

Radiation from medical imaging may induce cellular damage and increase the risk of cancer. While health care workers are restricted to an annual dose of 50 milliSieverts (mSv), the exposure to patients is not typically recorded. After breast-conservation therapy (BCT), patients are subjected to screening mammography, diagnostic breast imaging, and systemic surveillance imaging (SSI). Our objectives are to determine the cumulative radiation exposure of breast cancer survivors after completion of BCT, and to compare exposure levels in two historical cohorts. We also evaluated the indications of SSI.

We performed a retrospective study of 68 patients with stage I or II breast cancer who received BCT in 1997 or 2002. Cumulative radiation exposure during follow-up from all imaging attributable to the breast cancer diagnosis was recorded, including both breast and non-breast imaging. The indications for SSI were recorded.

In the first 5 years after BCT, patients received a median annual dose of 0.92 mSv with no difference between the 1997 and 2002 cohorts. A median of 90% of radiation exposure was due to mammography. From 1997 to 2002, the percentage of patients receiving computed tomography (CT) scans increased. Additional SSI occurred in 65% of patients, with the majority of tests ordered in the asymptomatic patient. Patients with nodal positivity were more likely to receive SSI (p = 0.03).

In the first 5 years after BCT, annual radiation exposure due to imaging was low. However, it seems prudent to consider the risks of radiation exposure when ordering potentially low-yield screening studies in asymptomatic patients.