Sole brachytherapy of the tumor bed after breast conserving surgery: A newradiotherapeutic strategy for patients at low risk of local relapse

The aim of the study was to test the hypothesis, if there were subgroups of early breast cancer patients in which sole brachytherapy (BT) of the tumor bed was a feasible and safe treatment option after breast conserving surge ry (BCS). Forty four prospectively selected patients with Stage I-TI breast cancer were entered into a protocol of postoperative tumor bed irradiation using interstitial high dose rate OTDR) implants. The HDR fractionation sc hedules were calculated according to the linear quadratic model. In 8 patie nts 7 x 4.33 Gy, in the other 36 patients 7 x 5.2 Gy were delivered to the tumor bed with 2 cm margin. The treatment planning was based on the 3 dimen sional (3D) reconstruction of the clipped excision cavity, catheters and sk in points. A conformal semi-3D dose planning was used. The side effects wer e assessed by mammograms, MRI- and clinical examinations. At a median follo w up of 20 (7-36) months 1 (2.3%) local and I (2.3%) regional failure was o bserved. Distant metastasis did not occure. The cosmetic results were judge d to be excellent in each case. G2 radiation side effects were observed in 2 (4.5%) cases. Postoperative sole BT of the tumor bed with careful patient selection and adequate quality assurance seems to be a feasible alternativ e to whole breast radiotherapy after BCS. Sole BT shortens the time of radi otherapy from 5-6 weeks to 5 days, and reduces the costs of treatment. The skin and volume sparing effect of interstitial irradiation may decrease the side effects of radiotherapy. A randomized study is in progress to define which subgroups of patients should be candidates for BT alone after BCS.