Contralateral Breast Dose in Breast Cancer Patients Undergoing Radiotherapy: A Case Study in a Radiotherapy Centre, South-west Nigeria

Abstract

The breast which is a highly radiosensitive organ has an increased risk of secondary malignancy in the contralateral breast (CB). As a result, the CB is regarded as an organ at risk during treatment. In this study, the contralateral breast dose for patients undergoing radiotherapy treatment of breast cancer was measured and analyzed. Thirty women aged over 18 years with invasive ductal carcinoma (T1-T2, N0) for 10 lumpectomy patients and (T3, N2) for 20 mastectomy was treated with radiotherapy for five days on a Cobalt-60 teletherapy unit within a period of three months. Medial tangential and lateral tangential fields was planned for lumpectomy patients while medial tangential, lateral tangential and supraclavicular was planned for mastectomy patients. Three TLD chips were placed on the surface of the contralateral breast for each patient, using the nipple as a reference point. The dosimeters were measured and compared with reference to surgery type, field size, depth and overall exposure time. The percentage mean dose evaluated at the medial and lateral side was 235.47% and 16.61% respectively for mastectomy patients; 135.27% and 12.21% respectively for patients with lumpectomy. 208.90% and 15.32% at the medial and lateral sides for a large field size, 186.13% and 14.73% respectively for a small field size. At short exposure time, the percentage mean dose measured was 207.70% and 14.19% at the medial and lateral sides and for long exposure time, 173.90% and 19.90% respectively. The findings in this study indicated that the contralateral breast is at risk of secondary malignancy, with the medial side experiencing a significant dose contribution in comparison with the lateral side of the breast.