Assessment of skin dose and its relation to cosmesis in the conservative treatment of early breast cancer.

A conservation technique has been developed for the treatment of early breast cancer which involved removal of the tumor, axillary clearance, tumor site implantation with Iridium-192 wires for a boost dose and subsequent treatment of the breast with radical megavoltage external beam therapy. Although the cosmetic results were satisfactory in the majority of the patients, for some it was rated as fair or poor. One variable factor which could have carried some morbidity was the dose of radiation received by the skin. In 51 patients, doses were measured at several points over the treated breast using Thermoluminescent Dosimetry (TLD) at the time of the iridium implant and during the subsequent external beam therapy. Development of skin pigmentation, oedema, and fibrosis were unrelated to the dose received by the skin but the findings suggested that doses greater than 50 Gy to the skin increased the possibility of late (greater than 24 months) telangiectasia over the boosted area. Treatment of tumors in the lower half of the breast, or in large breasts, was associated with a higher incidence of poor cosmesis. This may have been the result of varying posture on the interstitial dose distribution from the Iridium-192 wires and comparison of dose distribution in both supine and erect positions was carried out.