Unexpected toxicity in a patient treated with 3D conformal accelerated partial breast radiotherapy

With the publication of several trials demonstrating equivalence between partial breast irradiation and whole breast irradiation, the popularity of partial breast radiation has increased. Methods of delivery include interstitial brachytherapy, intracavitary brachytherapy, and 3D conformal irradiation, although the least amount of data exists on 3D conformal. Despite the relative paucity of data on 3D conformal, it is the most common method delivered on the National Surgical Adjuvant Breast and Bowel Project (NSABP) B-39 trial. To date, minimal toxicities and good cosmetic results have been associated with accelerated partial breast irradiation.

In this case study, we present a 64-year-old female patient, diagnosed with Grade 1 tubular carcinoma, who developed both expected and unexpected toxicities after 3D conformal accelerated partial breast irradiation.

Along with chest wall pain, she developed hyperpigmentation of the skin as well as fibrosis of the skin, pectoralis minor, and pectoralis major. The fibrosis she developed limited her comfortable range of motion in the ipsilateral arm. She also developed symptomatic fractures of the fourth and fifth ribs in the anterior axillary line. Upon fusing the treatment-planning CT with a diagnostic CT, it was evident that the rib fractures fell within the 100% isodose line of the 3D conformal plan.