Prospective Cohort Study to Evaluate Toxicity and Cosmesis between Interstitial APBI and Ultra-Hypo-Fractionated Whole Breast Irradiation in Patients with Early Breast Cancer

Abstract

Both interstitial multi-catheter brachytherapy based accelerated partial breast irradiation (APBI) and ultra-hypo-fractionated whole breast irradiation (WBI) with 5 fractions can complete treatment in a short time and result in lower treatment-related costs. Although data are available on their toxicity compared with conventional and hypo-fractionated regimens, there are few data directly comparing these two techniques. This prospective cohort study enrolled early breast cancer patients with negative ink margin, T1 or T2 stage, and tumor size of 3 cm or less, with 0 to 3 positive lymph nodes after adequate axillary dissection or negative sentinel lymph node biopsy (N0-1), regardless of receptor status (ER, PR, HER2neu). Of the total 31 patients, 15 received APBI with multi-catheter interstitial brachytherapy (35 Gy in10 fractions over 5 days with a minimum interval of 6 hours between fractions) and 16 patients received WBI (27 Gy in 5 fractions over 5 days) with either 3DCRT or VMAT technique. Acute toxicity was assessed using the RTOG toxicity grading and breast cosmesis was assessed using the Harvard breast cosmesis score. Toxicity and cosmesis were assessed immediately after treatment, after one month, and after three months of treatment. Results were compared between groups using the Mann Whitney U test. All patients completed a 3-month follow-up after completion of treatment. There was no statistically significant difference between the 2 groups in terms of highest grade toxicity (p = 0.97) and acute toxicity immediately after RT (p = 1.0) and after 1 month of RT (p = 0.91). However, at 3 months, more patients in the WBI group had a residual skin reaction than in the APBI group (p = 0.03). There was no statistically significant difference in breast cosmesis scores at any time point. 53.3%, 6.6% had grade 1 and 2 skin toxicities respectively immediately after RT in the APBI group and 62.5% of patients had grade 1 skin toxicity in WBI group. After 1 month 26.6%, 26.6% & 13.3% patients had grade 2, grade 1 and grade 3 toxicities respectively. In the WBI group, at 1 month, 50%, 18.7% and 12.5% patients had grade 1, 3 and 2 skin toxicities respectively. At 3 months, 42.8% and 7.1% of patients in the APBI group had grade 1 and grade 2 toxicities, respectively. In the WBI group, 78.5% and 7.1% of patients had grade 1 and 2 skin toxicities respectively. In this study, no difference in acute toxicity or breast cosmesis was demonstrated between APBI-based interstitial brachytherapy and ultra-hypo-fractionated WBI. Since both regimens can be administered within 5 days, the decision between them is challenging for both physicians and patients. This study can be considered hypothesis-generating and used for further planning of equivalence or noninferiority studies.