Comparing 5 and 15 Fractions for Whole Breast Irradiation After Breast Conserving Surgery

Adjuvant radiotherapy after breast-conserving surgery for breast cancer reduces the risk of locoregional relapse and ensures better overall survival. In recent years it has been found that hypofractionation in which the number of radiation sessions is reduced with a higher dose per session offers advantages for breast irradiation. Randomized studies showed that moderate hypofraction regimens in 15 or 16 fractions have the same effect in tumor control and toxicity, although the total dose is lower than the traditional 50 Gy in 25 fractions. In a randomized study from the United Kingdom (START-B trial) even a better disease-free survival was seen with 15 sessions than with 25 sessions and the long-term side effects were also less with the short schedule. This project proposes a clinical trial with an accelerated radiotherapy schedule in 5 sessions. It is expected that the accelerated schedule of 5 sessions over 10-12 days will have a number of radiobiological benefits: since a higher dose per session is given over a shorter period of time, it is expected that tumor control and survival will be higher. By reducing the total treatment time, the total dose is reduced, which may result in fewer radiation-related side effects and thus improve the quality of life. Apart from these radiobiological benefits, the shorter radiotherapy program reduces the number of treatment days from 15 to 5. This is not only more comfortable for the patients, but also increases the treatment capacity of the radiotherapy department. This opens up a possibility for the use of more complex techniques with fewer side effects such as radiation in the prone position. This project includes a randomized study comparing the accelerated schedule in 5 sessions with a hypofraction schedule of 15 sessions in patients who are irradiated on the entire breast after breast-conserving surgery. The primary endpoint is breast retraction (loss of volume) 2 years after radiotherapy.

Inclusion Criteria: * female patients with non-metastatic breast cancer, * age ≥ 18 years, * breast conserving surgery, * multidisciplinary decision of adjuvant breast irradiation, * informed consent obtained, signed and dated before specific protocol procedures Exclusion Criteria: * distant metastases, * bilateral breast irradiation, * history of previous radiation treatment to the same region * life expectancy of less than 2 years, * planned reconstructive surgery, * conditions making toxicity evaluation difficult (e.g. skin disorders), * patients unlikely to comply with the protocol (e.g. inability to return for follow-up visits or unlikely to complete the study).