Updates on the APBI-IMRT-Florence Trial (NCT02104895) Technique: From the Intensity Modulated Radiation Therapy Trial to the Volumetric Modulated Arc Therapy Clinical Practice

Abstract

Several phase 3 trials have demonstrated partial breast irradiation noninferiority compared with whole breast irradiation in terms of local control and similar or reduced toxicity. During recent years, especially owing to the COVID-19 pandemic, a growing interest in 5-fraction regimens emerged. The APBI-IMRT-Florence trial (NCT02104895) schedule (30 Gy in 5 fractions) might represent an appealing treatment option, being both a safe and effective partial breast irradiation schedule, with long-term reported results. The aim of this report is to support planners interested in implementing this technique and to warrant equal access to postoperative radiation treatment for most early breast cancer patient candidates. We report the current delivery technique optimized from the original protocol and the updated dose constraints for plan optimization. We also report a statistical analysis of dosimetric parameters on 50 patients treated in consecutive fractions. Treatment-related toxic effects were assessed using the acute radiation morbidity scoring criteria and late radiation morbidity scoring scheme from the Radiation Therapy Oncology Group and the European Organisation for Research and Treatment of Cancer. The mean volume of ipsilateral breast was 731 cm³ (standard deviation ± 450; range, 151-2205) and the mean planning target volume (PTV) was 139 cm³ (standard deviation ± 48; range, 55-259). There was good correlation between ipsilateral breast V_15Gy and the ratio between the PTV and ipsilateral breast volume (R² = .911). At a median follow-up of 4.5 years, 32% of patients (n = 16) developed any grade 1 acute toxic effect. No grade >1 toxic effect was observed. Sixteen percent of patients (n = 8) developed any grade 1 late toxic effect. No grade >1 toxic effect was observed. Physician-assessed cosmesis was reported as excellent (84%), good (14%), and fair (2%). The schedule of 30 Gy in 5 consecutive fractions might represent a safe, easy-to-deliver, and cost-effective option for appropriately selected patients affected by early breast cancer.