Five-year results of the very accelerated partial breast irradiation VAPBI phase I-II GEC-ESTRO trial

Background and purpose

The standard partial breast postoperative treatment for early breast carcinomas with multi-catheter interstitial brachytherapy (MIBT) requires 7–8 fractions in 4–5 days as used in the APBI GEC-ESTRO phase III trial. In 2017 the GEC-ESTRO Breast Cancer Working Group started a Phase I-II trial to study if very accelerated partial breast irradiation (VAPBI) using 3–4 fractions could be equivalent.

Material

81 patients with low-risk invasive carcinomas underwent high dose rate MIBT. Mean age was 68 (51–90); 33 women received 4 fractions of 6.25 Gy in 2–3 days, and 48 subsequent patients 3 fractions of 7.45 Gy in 2 days, 36 perioperatively and 45 postoperatively.

Results

Median follow-up was 62 months, with 5-year actuarial breast recurrence of 3.4 % (two cases). One patient died due to metastasis. Pigmentation changes in the entrance of tubes remained visible only in 12.3 % in long term (skin G1 toxicity). Fibrosis or slight induration (G1) in 22.2 % and G2 in 9.9 %. No case of telangiectasia has been described. Cosmetic outcome is good or excellent in 95 % and fair in 5 %. Four tumors located in the retroareolar area showed nipple retraction.

Conclusion

VAPBI with MIBT using four fractions of 6.25 Gy or three fractions of 7.45 Gy in two or three days offers good local control, with a 5-year rate of fibrosis G2 similar to the GEC ESTRO phase III trial. VAPBI in two days is a good choice to decrease the total time of treatment, which is beneficial for the patient and reduces the workload.