Changes in radiotherapy fractionation-breast cancer

Area of Science:

• Radiation Oncology
• Medical Physics
• Oncology

Background:

• Conventional radiotherapy fractionation (2.0 Gy/fraction) has long been standard for sparing normal tissues.
• Breast cancer exhibits a greater sensitivity to radiation fraction size compared to many other cancers.
• Decades of research and Level I evidence now confirm this differential response.

Purpose of the Study:

• To evaluate the efficacy and safety of hypofractionated radiotherapy in breast cancer treatment.
• To determine the optimal radiation fraction size for breast cancer based on radiobiological principles.
• To address concerns regarding hypofractionation in specific patient subgroups.

Main Methods:

• Analysis of four randomized trials with 10-year follow-up involving nearly 8000 patients.
• Testing of fraction sizes in the range of 2.7-3.3 Gy.
• Estimation of the alpha/beta (α/β) ratio for breast cancer.

Main Results:

• Robust estimates indicate an α/β ratio of approximately 3 Gy for breast cancer.
• This suggests no significant advantage in safety or effectiveness for conventional 2.0 Gy fractions.
• 15- or 16-fraction schedules are increasingly adopted as standard adjuvant therapy.

Conclusions:

• Hypofractionated radiotherapy (e.g., 15-16 fractions) is a safe and effective alternative to conventional fractionation for breast cancer.
• The radiobiological characteristics of breast cancer support the use of larger fraction sizes.
• Further research is exploring even shorter schedules (e.g., 5 fractions) and dose modulation strategies.