Intraoperative avidination for radionuclide treatment as a radiotherapy boost in breast cancer: results of a phase II study with (90)Y-labeled biotin

Purpose External beam radiotherapy (EBRT) after conservative surgery for early breast cancer requires 5–7 weeks. For elderly patients and those distant from an RT center, attending for EBRT may be difficult or impossible. We investigated local toxicity, cosmetic outcomes, and quality of life in a new breast irradiation technique—intraoperative avidination for radionuclide therapy (IART)—in which avidin is administered to the tumor bed and 90Y-labelled biotin later administered intravenously to bind the avidin and provide irradiation. Reduced duration EBRT (40 Gy) is given subsequently. Methods After surgery, 50 (ten patients), 100 (15 patients) or 150 mg (ten patients) of avidin was injected into the tumor bed. After 12-24 h, 3.7 GBq 90Y-biotin (beta source for therapeutic effect) plus 185 MBq 111In-biotin (gamma source for imaging and dosimetry) was infused slowly. Whole-body scintigraphy and SPECT/CT images were taken for up to 30 h. Shortened EBRT started 4 weeks later. Local toxicity was assessed by RTOG scale; quality of life was assessed by EORTC QOL-30. Results Of 35 patients recruited (mean age 63 years; range 42–74) 32 received IART plus EBRT. 100 mg avidin provided 19.5±4.0 Gy to the tumor bed and was considered the optimum dose. No side-effects of avidin or 90Y-biotin occurred, with no hematological or local toxicity. Local G3 toxicity occurred in 3/32 patients during EBRT. IART plus EBRT was well accepted, with good cosmetic outcomes and maintained quality of life. Conclusions IART plus reduced EBRT can accelerate irradiation after conservative breast surgery.