Question: What is fibrosis, and does radiation therapy for breast cancer cause it?
Answer: 'Fibrosis' is a medical term meaning scarring. When radiation is delivered, it affects many cells -- not only the cancer cells, but normal cells as well. Some cells that are particularly sensitive are the cells that line small blood vessels. When radiation is given, some of these very tiny blood vessels are damaged, and sometimes, destroyed. That makes some parts of tissue receive less blood supply. And some of that tissue, therefore, is not as well-nourished and as viable as it was in its pre-treatment state. In that case, some of those tissues can 'fibrose' or scar. And, the breast is susceptible to that. What we experience is a firmness to the tissue. And maybe even sometimes an area that feels almost like a mass or a recurrence.
I think that most patients get some scarring from radiation. Sometimes it is so subtle it cannot even be appreciated. In the occasional patient, it is much more apparent. We have relatively little basis in which to predict who is going to be that rare patient that sees much, much more scarring from their treatment. And one of the interesting research questions in radiation is to create some predictive assays that would say to us, "This particular patient is much more sensitive, and we have to modify the dose in some fashion to prevent scarring." The scarring itself has no inherent danger. It is much more a cosmetic issue and also one that affects, in some cases, the appearance of the mammograms, since scar tissue is more dense.