Prone Partial Breast Irradiation (PBI): a Prospective Randomized Trial

Despite the fact that less extensive experience than that of brachytherapy is available, PBI
delivery through an external-beam has many advantages. First of all, it is likely to be more
acceptable to the patient since it is non-invasive and it does not require a surgical
procedure or anesthesia. Moreover, since it is delivered after surgery, the pathological
analysis of the segmental mastectomy specimen is available to inform the selection of the
best candidates. In addition, EB-PBI is likely to become more widely reproducible, since it
does not rely on the experience and skills of the radiation oncologist performing the
brachytherapy implant. Besides, once the technique is established, it can be widely applied
at any facility provided with a linear accelerator, without the risk presented by some
brachytherapy approaches that can not be completed because of the unfavorable interplay of
patient's anatomy with the technical limitations of the applicator.

The women in this study will receive either 5 or 3 radiation fractions to the tumor bed. We
have chosen to study T1 post menopausal women because in this subset: 1) the tumor is small
enough to be treated by partial breast radiation 2) the odds of having multicentric disease
are low, making it ethical to avoid whole breast irradiation, 3) the most benefit from
reducing the radiation schedule from 5 to 3 could be expected.

All patients will receive either 8 Gy x 3 over 5 days, every other day or 6 Gy x 5 over 5
days, on five consecutive days

Inclusion Criteria:

- Post-menopausal women defined as either:

1. at least 2 years without menstrual period

2. patients older than 50 with serological evidence of post-menopausal status

3. hysterectomized patients of any age with FSH confirmation of post- menopausal
status

- pT1 breast cancer, excised with negative margins

- clinically N0 or pN0 or sentinel node negative breast cancer

Exclusion Criteria:

- previous radiation therapy to the ipsilateral breast

- presence of a proportion of DCIS in the core biopsy specimen which is compatible with
extensive intraductal component (EIC)