Indeterminate pulmonary nodules incidentally detected during radiological imaging completed for radiotherapy planning always creates dilemma for the oncologist. The purpose of this study is to evaluate the clinical significance of pulmonary nodules incidentally detected in patients undergoing locoregional radiotherapy for breast cancer and present a retrospective analysis of the natural progression of such nodules.

A retrospective review of computed tomography scans of breast cancer patients who underwent radiotherapy over a period of 3 years to screen out patients with indeterminate lung nodules was undertaken. This was correlated with the patient and tumour characteristics and the status of the disease at last follow-up.

Of the 132 patients reviewed 28 had indeterminate lung nodules. Of the 28 patients, four had progressive lung nodules on follow-up. Subgroup analyses did not show any significant correlation.

One fifth of patients may present with incidentally detected lung nodules. Multiple nodules, ER negative status and locally advanced breast cancer may point to a higher risk of these nodules progressing to metastatic cancer. There is no indication to stop locoregional therapy in the presence of indeterminate nodules, but close follow-up of high-risk group is recommended.