An accurate method for localization of the boost volume in breast radiotherapy

Patients with early stage breast cancer who are treated with adjuvant radiotherapy post-lumpectomy often receive a tumor bed boost with electrons. The tissue considered at high risk of local recurrence is defined from the surgical scar to the deepest portion of the tumor bed, which is ideally marked with radiopaque surgical clips. To adequately treat this tissue, one must superimpose the scar, surgical path and clips within the beam and choose an appropriate electron energy based on the deepest clip depth, while sparing low risk and cosmetically important tissues. Clip localization is therefore emphasized in the literature; however, published procedures do not adequately address how to meet all of the above goals. Additionally, CT planning alone cannot assess optimal coverage of tissue outside of the transverse plane, nor guarantee visualization of all clips. We have devised a method of boost planning based on localization of the surgical clips which may be accomplished in a single simulation session, utilizing two sets of orthogonal films, radiopaque skin surface markers, and FSD readings. Our procedure meets all of the above goals, is applicable to any field orientation that can be simulated, and can provide useful information for alternative techniques.