Stereotactic Body Radiation Therapy For Early-Stage Breast Cancer Using A Robotic Linear Accelerator

Standard radiation therapy for patients with breast cancer desiring breast conservation typically consists of lumpectomy followed by radiation. Radiation can either be delivered to the whole-breast or to part of the breast. Whole-breast radiation is typically given daily for 3–6 weeks depending on the dose/fractionation scheme. When partial-breast irradiation is given, often an implanted catheter is used to deliver a conformal dose of radiation to the lumpectomy cavity in an accelerated manner over one week. In properly selected patients, the results for partial-breast irradiation appear comparable to results for conventional whole-breast radiation. We examined the safety and efficacy of using an accelerated dose/fractionation schedule with a robotic linear accelerator for selected patients with early-stage breast cancer after lumpectomy. We reported on our technique and early results. Twenty-six consecutive patients with early-stage breast cancer were enrolled on an IRB approved breast protocol. Eligibility included Stage 0/I/II (<3 cm) Age >45, margins negative. One patient had fiducial markers placed by the surgeon. The other 25 patients had fiducial markers placed by the treating radiation oncologist using image guidance on a CT simulator with coordinate placement determined by the physics/dosimetry staff for optimal location. Patients were immobilized either using a thermoplastic cast with a hole removed around the areola to allow for reproducibility daily or with an alpha cradle to allow the breast to remain in its natural position. All patients received a dose of 3,000 cGy in 5 fractions of 600 cGy each given on five consecutive days. The median number of beams was 86. The median prescription isodose line was 71%. This isodose was chosen to allow for a more rapid fall of dose beyond the target volume to more accurately emulate HDR treatment. With a median follow-up of 27 months, (range, 3–48 months) all 26 patients (100%) remain locally controlled with no evidence of disease following treatment. RTOG Grade 1 dry skin desquamation occurred in 1 of 26 patients. The cosmesis was good-excellent in all 26 patients using the Harvard cosmesis scale. Stereotactic body radiosurgery for early-stage breast cancer using a robotic linear accelerator is very well tolerated and efficacious for selected patients desiring breast conservation after lumpectomy. More accrual and further follow-up will be required to see if these results remain durable.