I understand completely. I had the same fears as I have a nasty family history of pulmonary issues. Currently my lung tests and scan that I have had are very good. Before I even made the decision of which type of surgery to have, I had a conference call with my surgical oncologist and my lung doctor. My lung doctor , in practice for 40 years, has only seen 1 or 2 cases of radiation induced pulmonary fibrosis. But he and the surgical oncologist were citing much lower stats than I had read. I wasn't convinced. So, they arranged for a consultation with my radiation oncologist. We went over how the radiation is done and how she targets the tumor area while I am doing a deep inhalation breath hold. That technique helps move thelung out of the way a bit. At the consultation my radiation oncologist showed me the pictures of other patients and how little of the lung is at risk. I started my radiation on 1/30, 8 down - 7 to go. Following my 1st she showed me my pictures. The treatment she has designed for me the lungs are out of the target area. I was diagnosed with IDC stage 1A HR+HER2- tumor was 4mm with 8 mm clear margins and negative nodes. The tumor was so small that typing wasn't done as there might not been enough tissue to test. I urge you to talk with your radiation oncologist. Good luck.

@cctoo, did you reschedule to have radiation?
Like @crteelect, I also urge you to talk about your fears with your radiation-oncologist. They can help you make your decision based on facts specific to your medical history and not fear. Keep asking questions until you feel comfortable that you've understood the risks and the benefits of treatment.