Sustained Acceptable Cosmetic Outcomes And Local Control Following Accelerated Partial Breast Irradiation Using Ct-Guided Imrt In The Prone Position: Results From A Phase I/Ii Feasibility Study

Objective/Purpose External beam accelerated partial breast irradiation (EB-aPBI) can have potential challenges in daily reproducibility, although it has broader potential use than aPBI using brachytherapy. Image-guide radiotherapy (IGRT) can improve daily reproducibility and allow smaller treatment margins. Our institution utilized IG-IMRT to administer EB-aPBI in the prone position in a Phase I/II study to increase dose homogeneity, conformality, normal tissue avoidance, and reliable targeting. Our preliminary results and toxicity were promising. Here we report final physician- and patient-reported cosmetic outcomes from this prospective trial. Materials and Methods Women with node-negative invasive breast cancer or DCIS, tumors less than 3.0 cm, a negative sentinel lymph node biopsy, and surgical clips demarcating the lumpectomy cavity underwent prone EB-aPBI using IG-IMRT on an IRB-approved phase I/II study. The lumpectomy PTV represented a 2.0 cm lumpectomy cavity expansion. 38.5 Gy was delivered in 10 fractions over 5 days, such that 95% of the prescribed dose covered greater than 99% of the PTV. Dose constraints for the whole breast, lungs and heart were met. Results Twenty patients were enrolled, with a median patient age of 61.5 and a mean tumor size of 1.0 cm. 35% of patients had DCIS. At a median follow-up of 18.9 months, 40% and 10% of patients had G1 and G2 fibrosis, respectively, and 95% of patients had good to excellent physician-assessed cosmesis. At a median follow-up of 60.0 months (range 54-79 months), physician-assessed cosmetic outcome was good to excellent in 80%, with 30% and 20% of patients experiencing G1 and G2 fibrosis. Patient-reported outcomes at one year yielded 90% of patients with good to excellent cosmetic outcomes. At 3 years, 75% of patients reported good to excellent cosmesis. Eighty-eight percent of patients were completely satisfied with the treatment and results, and 94% of patients would choose aPBI again. With one local recurrence, the actuarial five year rate of local control was 95%. Conclusions These data demonstrate that EB-aPBI in the prone position using IG-IMRT continues to yield acceptable cosmetic outcomes at longer term follow-up, and a very high percentage of patients would choose this treatment again. (Supported by Komen Grant: BCTR0504070). Citation Format: Carmen Bergom, Phillip Prior, Kristofer Kainz, Natalya V Morrow, Ergun E Ahunbay, Alonzo Walker, X Allen Li, Tracy Kelly, Adam D Currey, Julia White. Sustained acceptable cosmetic outcomes and local control following accelerated partial breast irradiation using CT-guided IMRT in the prone position: Results from a phase I/II feasibility study [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P1-15-17.