Brachy therapy techniques for the treatment of breast cancer

Despite excellent results from standard tangential field treatment, numerous limitations of this technique exist. High dose regions near the skin in the resultant inhomogeneous dose distribution may produce suboptimal cosmetic results. Also, dose to a small volume of ipsilateral lung, and in left-sided patients, dose to small volume of heart, may be significant in some cases and result in complications. Use of intensity modulated beams has been tried to create better uniformity of dose and reduction of dose to the organs-at-risk. Helical tomotherapy as well as conventional static IMRT has been used for some difficult cases including the use of field-in-field technique. Also, in many early breast cases, instead of treating the whole breast, partial breast irradiation has proven to be equally effective. Since the tissue immediately surrounding the lumpectomy cavity is only considered to be at risk, partial breast treatment volumes are relatively small, enabling delivery of large dose per fraction. So, the whole treatment is delivered within a week, making accelerated partial breast irradiation (APBI) quite convenient for selected early stage breast cancer patients. External un-modulated and intensity modulated beams have been used for partial breast treatments. Also for interstitial brachytherapy for APBI, several applicators are now commercially available. Brachytherapy techniques concentrate dose in tumor by placing radiation sources directly in the target volume. The dose drops off rapidly beyond the implant, thereby sparing surrounding normal tissues. Comparison of external beam techniques with brachytherapy applications for APBI will be presented. (author)