Inadequacy of iridium implant as sole radiation treatment for operable breast cancer

In order to avoid a prolonged course of external irradiation as part of breast conservation therapy, 27 patients received an iridium implant to the primary tumour bed as sole radiation treatment. Surgery was standardised comprising tumourectomy and axillary clearance. Using a rigid implant afterloading with iridium192 wires, 55 Gy was delivered on a continuous basis over 5 days. After 6 years median follow-up, relapse of cancer within the treated breast has occurred in 10 of the 27 patients (37%). Compared with historical controls treated by similar surgery and iridium192 implant (20 Gy) with external radiotherapy (46 Gy), there was a significantly increased breast relapse rate in those treated by iridium implant alone. However, the incidence of distant metastases and overall survival was similar. Thus, a continuous iridium192 implant delivering 55 Gy in 5 days is not an effective means of achieving local control in patients with operable breast cancer.