Outcomes in Patients with HER2 Overexpressing and Triple Negative Phenotypes Treated with Partial Breast Irradiation using Mammosite Brachytherapy
Neha Sharma, M.D., Susan Lee, M.D., Karen Karsif, M.D., Akkamma Ravi, M.D., Dattareyudu Nori, M.D.
Department of Radiation Oncology, New York Hospital Queens, Flushing, NY.
Purpose: To evaluate outcomes in patients with HER2 overexpressing and triple negative phenotypes treated with partial breast irradiation using Mammosite high dose rate brachytherapy.
Materials and Methods: Seventy-three patients were treated in our department from March 2004 to October 2008 with Mammosite high dose rate brachytherapy following surgical resection as a part of breast conservation therapy. All patients received 3400 cGy delivered in ten fractions, twice daily approximately six hours apart. All patients had stage I invasive breast carcinoma, ranging from T1a to T1c tumors and underwent sentinel lymph node biopsy and were found to be node-negative. In addition, all patients had invasive ductal carcinoma, negative surgical margins, and grades 2 or 3 disease. From this group, seven patients had triple negative phenotypes and four patients had tumors that were estrogen receptor negative, progesterone receptor negative, and HER2/neu positive (HER2 overexpressing). Tumors were located in upper outer quadrant in ten patients, and in the upper inner quadrant in one patient. Three of seven patients from the triple negative group received chemotherapy prior to the initiation of radiation treatments and all patients with ER negative PR negative HER2/neu positive tumors received chemotherapy and herceptin prior to radiation. One patient was noted to have lymphatic vascular invasion. Patients ranged in age from 53-87 years, with median age 62 years. All patients were post-menopausal. Median time to follow-up was 32 months (range 16 – 52 months).
Results: As of last follow-up, no patients have developed locoregional recurrence or distant metastases. One patient from the HER2 overexpressing group developed a new primary invasive disease in the opposite quadrant of the treated breast. This tumor was found to be triple negative. One additional patient from triple negative disease group died from complications of advanced papillary serous endometrial cancer. All other patients are surviving with no evidence of disease.
Conclusions: With our available follow-up, patients with HER2 overexpressing and triple negative stage I breast carcinoma appear to have acceptable locoregional control rates when treated with partial breast irradiation using high dose rate brachytherapy.