Is it possible to have diffuse, bilateral pulmonary fibrosis as a late side effect of unilateral radiation therapy for breast cancer?   

The only context you may see this is in a patient with underlying Interstitial Lung Disease (ILD). I had a woman with a small pulmonary nodule adjacent to the heart and was unresectable. She had moderately severe ILD, and I used a proton plan to try and keep the low dose RT out of the rest of the lu...

I have seen fibrosis within and outside radiation field, but diffuse bilateral fibrosis would be very unusual. One should look for different causes for this, including the effects of systemic treatment like herceptin.  

I have had a case of a lady with this clinical picture which later was diagnosed with BOOP. The clinical picture is very much like bilateral pneumonitis.