Hypofractioned Radiation Therapy in the Treatment of Partial Breast: 30 Gy in Five Consecutive Fractions

Abstract

Background and Purpose: Recent prospective studies have explored the partial breast irradiation (PBI) for patients with early-stage breast cancer using different technical approaches. The purpose of this study is to explore feasibility, tumor control and acute and late toxicity of a specific hypo-fractionated 3D-CRT when treating postmenopausal patients with early breast cancer with partial breast irradiation, using five fractions in five consecutive days. Materials and Methods: Ten patients, aged ≥ 70 underwent breast conservative surgery for invasive breast carcinoma with a complete microscopic resection; no lymphovascular invasion was found and negative axillary node status was assessed. Metal clips were positioned in the surgical bed at the time of surgery. All of the patients provided an informed consent for breast irradiation. Seven patients received Tamoxifen. Of the ten patients, five were treated for left breast disease, and five for right breast disease. The dose fractionation schedule was 3000 cGy delivered to the isocenter in 5 fractions (600 cGy/fr) using 6 MV photons. According to the linear quadratic model and an α/β ratio of 4 Gy this prescription is equivalent to 50 Gy in a standard 2-Gy fractionation schedule. Patients were treated in the supine position. A comercial breast board was used as immobilization device in order to keep the arms of the patient raised. The clinical target volume (CTV) was drawn with a uniform 1-cm three-dimensional margin around the surgical clips. The CTV was limited to 3 mm from the skin surface and 3 mm from the lung-chest wall interface. A three-dimensional margin was added to the CTV to obtain the planning target volume (PTV). The ipsilateral and controlateral breast, the ipsilateral and controlateral lung, heart and spinal cord were contoured as organs at risk (OAR). The treatment was developed using Precise Plan Treatment Planning System and four no-coplanar fields. The constraints used have been: uninvolved breast (ipsilateral breast-PTV): V15 ≤ 50%; heart: V3 ≤ 10%; ipsilateral lung: V10 ≤ 20%; controlateral lung: V5 ≤ 10% and controlateral breast: maximum dose ≤ 1 Gy. We required PTV coverage of ≥ 90%. Patient set-up was verified every day before treatment using portal images. No tumour bed boost was delivered. Clinical assessments of early normal tissue reaction were carried out every day during radiotherapy and 10 days after the end of the treatment. After radiotherapy, we visited all patients every 3 months during the first 2 years and every six month thereafter. Frontal and lateral pictures of the breast were taken on the first day of treatment (baseline), at the end of treatment, 10 days after the end of treatment and at the first follow-up. Any change in breast appearance compared with the baseline picture was scored on a four-point RTOG for acute and late radiation morbidity scoring scale. Results: No local or distant recurrences was observed and then confirmed by mammograms performed every year and breast ultrasound performed every six months. For acute and late toxicity, only 2 patients developed acute effects at the end of the treatment. Conclusion: The clinical outcomes observed in ten patients demonstrate a good feasibility of the schedule adopted both in terms of tumour control and acute and late toxicity, with good cosmetics results. Long term follow-up and a large number of patients will be needed for full evaluation.