CASE REPORT Breast Cancer Recurrence after Inadvertent Malpositioning of a Partial Breast Radiation Catheter Stephanie A. Valente, DO,* Gary M. Levine, MD,* ,  Lisa E. Guerra, MD,* ,à and Melvin J. Silverstein, MD* ,à *University of Southern California, Keck School of Medicine, Division of Breast and Soft Tissue Surgery;   Hoag Memorial Hospital Presbyterian, Department of Breast Radiology; à Hoag Memorial Hospital Presbyterian, Department of Breast Surgery n Abstract: Accelerated partial breast irradiation (APBI) is an alternative to receiving whole breast radiation in carefully selected patients. Because breast cancer local recurrence rates are low and follow-up has been short-term, the exact cause of recurrences after APBI has been difficult to evaluate. We report the first case of documented radiation balloon catheter malpositioning that resulted in local recurrence. Patients undergo CT imaging of the breast after radiation balloon catheter placement for radiotherapy treatment planning, which evaluates adequate conformance of the balloon to the surrounding breast parenchyma and confirms a >7 mm distance between the balloon surface and the skin surface. Although true local recurrences are rare in appropriately selected partial breast irradiation candidates, inadvertent malpositioning of the radia- tion treatment catheter can increase the risk. This case is presented to illustrate the importance of comparing CT radiation planning images, with treatment catheter in place, to the original diagnostic breast imaging studies to confirm proper catheter positioning (in addition to measuring balloon to skin distance and conformance) prior to initiating radiotherapy. n Key Words: accelerated partial breast irradiation, apbi, breast cancer, mammosite, recurrence F or select patients with early stage breast cancer elect- ing to undergo breast conservation therapy with lumpectomy and radiation therapy, accelerated partial breast irradiation (APBI) is an alternative to whole breast radiation. APBI is a technique that treats the lumpectomy cavity plus an additional 1–2 cm margin of surrounding breast tissue. The rationale for APBI is that pattern analy- sis has shown that ipsilateral breast local failures occur within close proximity to the original tumor site (1–3). Thus, APBI only targets the area of breast that has dis- ease, sparing the surrounding healthy tissues from the effects of radiation. Because APBI offers a shorter radio- therapy treatment time (1 week compared to 5–7 weeks), many find this a convenient and acceptable alternative to whole breast radiation. Most importantly, APBI has been shown to yield similar local control rates when compared to whole breast radiation (4,5). Since its approval in 2002 by the Food and Drug Administration, MammoSite balloon catheter brachytherapy has increasingly been used as a form of APBI. For this technique, a balloon radiation catheter is implanted at one of two different times by the phy- sician: either at the time of the surgery, or in the office after surgery once final pathology confirms adequate margins. The office placement technique is performed under ultrasound guidance and identifies the residual lumpectomy seroma cavity to guide proper balloon position. Alternatively, at the time of surgery, sur- geons can elect to place a temporary cavity evaluation device to maintain the lumpectomy cavity while awaiting final pathology results. Once final pathology is confirmed, the cavity evaluation device can be exchanged with the radiotherapy balloon catheter for APBI treatment or it can be removed. Because local recurrence rates are low and follow-up has been short-term (5–7), the exact causes of recurrence after APBI have been difficult to evaluate. We report the first case of documented balloon radiotherapy catheter malpositioning that resulted in local recurrence. CASE REPORT A 64-year old female presented to an outside physi- cian with a left breast infiltrating ductal carcinoma Address correspondence and reprint requests to: Stephanie A. Valente, DO, University of Southern California, Keck School of Medicine, Division of Breast and Soft Tissue Surgery, 1441 Eastlake Avenue, Suite 7415, Los Angeles, CA 90033, USA, or e-mail: stephanie.a.valente@gmail.com. DOI: 10.1111/tbj.12012 Ó 2012 Wiley Periodicals, Inc., 1075-122X/11 The Breast Journal, 2012 1–5