Preliminary outcomes of accelerated partial breast irradiation by interstitial multicatheter brachytherapy with intraoperative free-hand catheter implantation in early breast cancer.

BACKGROUND: To evaluate the clinical feasibility of interstitial brachytherapy by intraoperative free-hand catheter implantation in the treatment of early breast cancer after breast-conserving surgery.

METHODS: Between January 2018 and December 2019, 44 patients with early breast cancer after breast-conserving surgery (BCS) who met the inclusion criteria ≥ 45 years old, invasive carcinoma ≤ 3cm or ductal carcinoma in situ (DCIS) <2.5cm, estrogen receptor (ER) positive, lymph node negative, surgical margin negative, no distant metastasis, and an ECOG performance score ≤ 1 were enrolled in this phase II single arm study. The postoperative irradiation field includes the tumor bed plus 2 cm margin in all directions, except in the anterior-posterior direction. The total prescribed tumor dose was 3400cGy delivered in 10 fractions twice daily at 6-hour intervals. The primary endpoints were acute side effects, late treatment-related toxicity, and cosmetic outcome. The secondary endpoints were local recurrence-free survival (LRFS), regional recurrence-free survival (RRFS), distant metastasis-free survival (DMFS), and overall survival (OS).

RESULTS: The median follow-up time was 33.5 months (mean, 32.9 months; range 20-43 months). The cosmetic results were good to very good in 92.3% of the questionnaire respondents. The acute toxicities were mild, and no acute grade 3-4 toxicity was noted. Wound infection was noted in 2 patients (4.5%). There was only one event of regional lymph node recurrence in one patient. The 3-year LRFS, DMFS, and OS were 100%, and RRFS was 94.7%. For two patients who had a positive lymph node based on their final pathology reports, postoperative irradiation, including whole breast and regional lymph nodes, was added.

CONCLUSION: APBI using interstitial brachytherapy with the intraoperative free-hand catheter implantation technique provides an alternative method of postoperative radiotherapy for selected patients with early breast cancer after BCS with acceptable toxicities.