Prone Whole-Breast RadiationTherapy Versus Supine Whole-Breast Radiation Therapy Imaging

Radiation therapy to the breast has remained a standard practice for breast conserving
therapy. Because of the location of the heart and lungs when patients are positioned
face-up, whole breast radiation therapy has been reported to increase the risk of damage to
the heart a few years after treatment until at least 20 years after exposure, and may affect
cardiovascular mortality. Also, patients receiving whole breast radiation therapy are at an
increased risk for development of secondary lung malignancies. Recent studies have
demonstrated a significant reduction in dose to the heart and lungs when treated in the
face-down position. Similarly, correcting for the movement of breathing (respiratory gating)
in the face-up position has also become an available option for reducing unwanted dose to
the heart and lungs, particularly in left sided breast cancers. No study to date has
compared these newer organ-sparing techniques head-to-head for early stage breast cancer.

It is institutional policy to perform CT simulation in left-sided breast cancer patients
with and without the respiratory gating (this is one CT scan), in the face-up position. It
is also standard of care to perform the face-down CT simulation in large breasted women.
Both of these simulations are meant to reduce the exposure of the heart and lungs to
radiation.

In this study, all left-sided breast cancer patients that consent will receive face-up CT
simulation with and without gating AND face-down CT simulation, regardless of breast size;
thus, each patient is their own control.

The treating physician will determine which of the two simulations, if any, offers better
protection to each patients' heart and lungs. Two dosimetrists will be required to
independently verify planned dosimetry with all treatment setups. Treatment will be planned
in standard fashion using the best of the two plans.