2721 - Early Outcomes of Accelerated Partial Breast Irradiation with Interstitial Brachytherapy vs. Extreme Hypo-Fractionated EBRT in Indian Females with Early Breast Cancer - A Randomized Controlled Trial

P. Rana¹, S. Sushant¹, S. K. Saini¹, D. N. Sharma¹, S. A. R. Swarna¹, S. Sanyal¹, S. Bhasker¹, S. Gupta¹, K. P. Haresh¹, S. Mallick², and S. V. S. Deo¹; ¹All India Institute of Medical Sciences, New Delhi, India, ²National Cancer Institute, All India Institute of Medical Sciences, New Delhi, India

Purpose/Objective(s): The study aimed to compare acute toxicity, cosmesis, and local control of APBI with Interstitial Brachytherapy (IBT) versus Extreme Hypo-Fractionated External Beam Radiation (EHy-EBRT) in early breast cancer. Materials/

Methods: The study enrolled patients with early breast cancer who underwent upfront breast conservative surgery (BCS) with negative margin, T1/T2, size up to 3.5 cm, 0-1 lymph nodes at axillary dissection or sentinel node biopsy, regardless of receptor status. A total of 22 patients after BCS were randomized into 2 arms with 11 patients each. In Arm-A, APBI was done with multi-catheter IBT (35 Gy /10 fr / 5 days) with minimal gap of 6 hours and in Arm-B, EHy-EBRT (28 Gy /5 fr /5 days) with IMRT. Adjuvant hormone therapy and chemotherapy were administered as needed. Acute toxicity was assessed using RTOG grading and cosmesis was assessed using Harvard breast cosmesis score, at 15 days, after 1, 3, and 6 months of RT. Local control was assessed clinically at 6 months. Results were compared between arms using Mann-Whitney U test.
Results: All 22 patients were treated as per protocol. The age of patients in Arm-A ranged from 40 to 68 years (M 53.4, SD 10.5) and in Arm-B ranged from 40 to 75 years (M 59.7, SD 8.9). The laterality was evenly distributed in both arms, and all patients underwent BCS + SLNB/ALND. Of the 22 patients, 20 were HR-positive, of which 9 were in Arm-A and 11 in Arm-B. 2 patients with TNBC were in Arm-A. The mean CTV volumes in Arm-A and Arm-B were 45.9±16 and 75.9±32, respectively. All patients followed-up till 6 months after RT. There was no significant difference in breast cosmesis scores at any time point. No statistically significant difference was noted between the 2 groups in acute toxicities at 15 days (p = 0.38) and 1 month of RT (p = 0.67). Acute toxicities at 3 and 6 months were also comparable with p-values, 0.9 and 1.0 respectively. 15 days post-RT, in IBT group, 45.4% had grade 1, 45.4% had grade 2 and 9% had grade 3 skin toxicity, whereas in EHy-EBRT arm 27.2%, 72.7% had grade 1, 2 toxicity respectively with no grade 3 toxicity. After 1 month, in IBT group, 45.4%, and 54.5% of patients had grade 1 and grade 2 skin toxicities respectively with no grade 3 toxicity. In the EHy-EBRT group, at 1 month, 54.5%, 36.3% and 9% of patients had grade 1, 2, and 3 skin toxicities respectively. At 3 months, all patients in the IBT group had grade 1 skin toxicity, whereas 90.9% and 9.0% of patients in the EHy-EBRT group had grade 1 and 2 skin toxicities, respectively. Similarly, at 6 months, all patients in both arms had only grade 1 skin toxicities with none reporting grade 2 or 3 reactions. None of the patients had any clinical signs of local or distant failure at 6 months in either arm.
Conclusion: Extreme hypofraction as partial breast irradiation is safe and has comparable toxicities, cosmesis, and short-term local control to interstitial brachytherapy. This will significantly reduce the burden of treating patients twice a day with IBT, as well as overcome the apprehension for anesthesia and operative procedures in IBT.