Permanent breast seed implant for partial breast radiotherapy after partial mastectomy for favorable breast cancer: Technique, results, and applications to various seroma presentations.

Adjuvant partial breast radiotherapy is the standard of care for early-stage favorable breast cancer. We report dosimetry, acute and late tolerance for 67 permanent breast seed implants. From July 2012 to October 2018, 67 postmenopausal women with unifocal pT1pN0 invasive ductal or ductal carcinoma in situ received partial breast radiotherapy using stranded Pd-103 seeds after breast-conserving surgery, delivering 90 Gy to the seroma + margin (1.25-1.5 cm), planned with computed tomography simulation and performed as an ultrasound-guided outpatient procedure. The planning and postimplant computed tomography images were fused for seroma delineation for postimplant dosimetry. Evaluations were performed at 1, 2, 6, and 12 months and then annually. Although patient acceptance is high, only 40% met technical requirements of seroma volume, location, and visibility. For 67 patients, the median seroma volume was 6.6 cc, PTV 61 cc, and number of needles 18. In day 0 dosimetry, median seroma D90 dose was 132 Gy; seroma + 5 mm, 106 Gy; and seroma + 10 mm, 80 Gy. Peak reaction at 6 weeks is limited to the implant site: 51% grade 1 erythema and 12% focal desquamation. Late reactions (>2 years) are generally minimal: 35% no sequelae, 43% localized fibrosis, 20% mild telangiectasia (6% moderate but asymptomatic), 22% contour change. At minimum 6-month follow-up, 94% were "very or totally satisfied." Recurrences (median follow-up: 3.3 years) were one in breast (different quadrant) and 2 contralateral. Three patients have had biopsies of fibrosis, all negative for malignancy. Our experience with permanent breast seed implant is favorable with a high patient acceptance and satisfaction, excellent early efficacy, and very satisfactory cosmesis.

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