Partial Breast Irradiation, or PBI involves treatment of only a portion of the breast, meaning the lumpectomy cavity plus a limited amount of surrounding tissues, instead of the more commonly treated whole breast. Since a smaller volume of breast tissue is irradiated, treatment times are significantly shorter than conventional treatment.
Interstitial brachytherapy, or IRT, delivers radiation from within the tumor cavity. A device, such as a catheter or a needle, is placed into the treatment area, and radioactive seeds are inserted into the catheter during treatment, then removed afterward. This means that radiation exposure is limited to a short distance of surrounding tissue. Healthy tissue near where the tumor was is less affected by brachytherapy than when external beam radiation is used. Interstitial brachytherapy for breast cancer is much faster than external beam radiation. It is also sometimes used as a boost, when external beam radiation treatments have been completed.