@brooklyn22 yes there are radiologists out there that are not comfortable with 5 day target when a margin is close but not touching, because they're waiting on studies that can replicate the original research. Practice changes usually don’t happen until multiple studies show the same result. Its for our safety.
I only had a 1 mm margin, but 5 days were allowed because it was just a focal point margin, and, because I was at a comprehensive cancer center that does a lot of research.

My fear is that 5 day radiation might be pushed as a good solution because the insurance companies like the idea, and easily approve it. Same with the wait and see idea of limiting surgery. Shorter radiation days and no surgery might be a good option for some, but it becomes worrisome when it is the protocol du jour.

Know the risks and as much about the outcomes as possible before making a decision.
5 day radiation, is great because its short, it usually causes less outer skin damage, and early research shows it provides equivalent recurrence protection.
My outcomes after 3 1/2 years? Hardening of breast tissue, massive thickened skin, higher risk of seroma with future surgeries, higher risk when shaping breast due to thickened skin.
Whether this would be less with 15 radiation sessions I’ll never know. But the idea of the higher number of sessions with lower dose is to prevent these effects.

The outcomes of long/short radiation might make a difference to someone who knows they’re likely to have surgery after radiation or reconstruction on the exiting breast after radiation.
Higher rads=likely damage=less flexible soft tissue