Is there evidence to support partial breast irradiation with daily fractionation?

As I understand it, the BID fractionation (e.g. 340 BID) that was used in the early APBI studies were largely for patient convenience. There is a potential anti-cancer benefit as well due to less repopulation during RT, but one would suspect that this is not a big effect since these breast cancers are not thought to have a particularly fast rate of growth (particularly the low-grade, and favorable, lesions that are often present with APBI is used in lieu of whole breast RT). So, I would think th...

I agree with @Dr. First Last. Also, there are a number of publications that detail once daily fractionation using external beam delivery. There is a published randomized phase III trial from Florence that used 6 Gy x 5 delivered every other day. I believe this same fractionation regimen has been published by NYU for the prone position, and probably many others.

Livi L, Meattini I, Marrazzo L, Simontacchi G, Pallotta S, Saieva C, Paiar F, Scotti V, De Luca Cardillo C, Bastiani P, Orzalesi L, Casel...

As @Dr. First Last mentioned, the Florence trial used 6 Gy x 5 compared to the standard arm of 50 Gy in 25 fractions follwed by a boost. At a median f/u of 5 years, LR was 1.5% in both groups. There were significant differences in acute toxicity, late events and cosmesis all favoring the APBI group.

@Dr. First Last also published results a prospective institutional trial of 100 patients with IDC treated with PBI 6 Gy x 5. At a median follow up of 64 months, there was 1 IBTR and one CBC. Cosmesis ...

Although it will be very interesting to see the long-term results of the NSABP B39 trial, the interim analysis of the rigorous cosmetic and toxicity assessment in the RAPID randomized controlled trial demonstrating inferior outcomes with twice daily fractionation (3.85 Gy x 10) compared with whole breast irradiation suggests that determining the optimal PBI dose/fractionation regimen should be an area of ongoing investigation. There is compelling clinical/rabiobiological evidence led by Dr. Bent...

Another study presented at ASTRO was using START or Canadian fractionation to partial breast (September 2004 Volume 60, Issue 1, Supplement, Pages S273–S274). Since most recurrences are local and since we have data demonstrating that tolerance with these fractionation schemes is good, this should be considered. We'll never have a study in this country looking at fractionation issues again.

Given some of our patient's requests, we have considered spltting the BID treatment (ie 2 days one week, three the next) instead of the 5 consecutive treatments which sometimes puts their treatments on the weekends. Any data on splitting the BID course for APBI?