ESTRO 2023

Session Item

Breast

Session Code: 6006

Session Type: Poster (Digital)

Track: Clinical

Stereotactic APBI for early-stage breast cancer: 3-year outcomes of a prospective registry

Jonathan Cantalino, USA

Presentation Number: PO-1249

Abstract

Abstract Title:

Stereotactic APBI for early-stage breast cancer: 3-year outcomes of a prospective registry

Authors:

Jonathan Cantalino¹, Monica Pernia Marin², David D'Ambrosio³, Arica Hirsch⁴, Malika Danner¹, Sonali Rudra¹, Simeng Suy¹, Sean Collins¹, Dawn Matsanka⁵, Michael Good⁵, Jing Feng⁵, John Lamond⁵, Deborah Markiewicz⁵, Rachelle Lanciano⁵, Olusola Obayomi-Davies⁶, Brian Collins⁷

¹Medstar Georgetown University Hospital, Department of Radiation Medicine, Washington, DC, USA; ²The George Washington University Hospital, Geriatric and Palliative Care Division, Washington, DC, USA; ³Community Medical Center, New Jersey Cyberknife, Toms River, NJ, USA; ⁴Advocate Lutheran General Hospital, Illinois Cyberknife, Park Ridge, IL, USA; ⁵Crozer Keystone Health Care Center, Philadelphia Cyberknife, Philadelphia, PA, USA; ⁶Wellstar Medical Group, Department of Radiation Oncology, Marietta, GA, USA; ⁷Tampa General Hospital, Department of Radiation Oncology, Tampa, FL, USA

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Purpose or Objective

Outcomes following adjuvant accelerated partial breast irradiation (APBI) in select women with early-stage breast cancer are comparable to whole breast irradiation. Robotic stereotactic accelerated partial breast irradiation (RSAPBI) with fiducial tracking is an attractive adjuvant treatment option, but limited outcomes data are available for this approach. We report 3-year outcomes for a prospective multi-institutional registry treating select women with RSAPBI.

Material and Methods

Post-menopausal women with DCIS and Stage IA breast cancer were treated over a five-year period extending from November 2015 to November 2020 and were followed for a minimum of 24 months. Treatments were delivered with a robotic radiosurgery system. Four gold fiducials were implanted around the lumpectomy cavity prior to the start of treatment for tumor bed delineation and target tracking. The CTV was defined as the lumpectomy cavity with a uniform 5-15 mm expansion confined to the breast tissue and the PTV was defined as the CTV with a 0-5 mm uniform expansion. The PTV was prescribed 30 Gy in 5 fractions. Disease status, toxicity, and cosmetic assessments were completed at 4 weeks, 3 months, 6 months, 12 months, 18 months, 24 months and yearly intervals thereafter for five years. Cosmesis was scored per the Harvard Breast Cosmesis Scale and toxicity was graded per RTOG toxicity criteria.

Results

Eighty-one patients (median age 68 years) with hormone receptor-positive tumors were treated over a median 9 days (range, 5-15). Sixty-eight women had invasive ductal carcinoma (84%) and thirteen had DCIS (16%). The median treated PTV was 108 cm3 (IQR 66-156) and the median prescription isodose line was 81% (IQR 79-83). The median CTV expansion was 10 mm (range 5-10) and the median PTV expansion was 3 mm (range 0-5). At a median follow up of 3 years there was one new ipsilateral breast tumor occurrence with no local, regional, or distant treatment failures. Overall survival was 95%, with no deaths due to breast cancer. Grade 1 skin toxicity was seen in two women at 3 years. No grade 2 through 4 toxicity of any kind was observed. Cosmesis at last follow-up was rated excellent for 84% and good for 15% of patients.

Conclusion

The 3-year outcomes of this prospective multi-institutional registry suggest that RSAPBI with fiducial tracking is a practical, effective and well-tolerated technique for the adjuvant treatment of early-stage breast cancer. Our current prospective multi-institutional registry is now enrolling elderly patients (>70 y/o) with early-stage breast cancer who decline surgery and wish to complete RSAPBI treatment alone.