Oral Presentation Joint 2016 COSA and ANZBCTG Annual Scientific Meeting

Critical decision making in Radiation Therapy for breast cancer (#3)

Boon Chua 1
  1. Peter MacCallum Cancer Centre (UNSW and Prince of Wales Hospital from November 2016), Melbourne

The EBCTCG meta-analysis in 2005 demonstrated for the first time that radiation therapy (RT) after breast-conserving surgery or mastectomy not only reduced local-regional recurrence but also improved long-term survival. For every 4 local recurrences avoided at 5 years, one breast cancer death was avoided at 15 years. In the updated analysis in 2011, the EBCTCG adopted 'any first recurrence' as the primary endpoint for the effect of RT primarily due to its established systemic effect in reducing both local and distant recurrence. One breast cancer death was avoided by year 15 for every four recurrences avoided by year 10. Early detection enabled by population-based mammographic screening and advances in multidisciplinary breast cancer management underpin the falling local recurrence rates over the last few decades and hence, the significance of tailoring RT utilisation according to the local recurrence risks of individual patients to reduce over-treatment of low-risk patients. The recent development of breast cancer classification based on gene expression profiles has shown that each intrinsic subtype is associated with distinct clinical outcomes, and luminal-A subtype is shown in early studies to be associated with the lowest local recurrence rate compared to the other subtypes. Clinical trials are in progress to improve the prognostic precision for local recurrence to identify patients with low risk of local recurrence who may safely omit RT.

The other advances in RT after conservative surgery include (1) hypofractionated whole breast RT after conservative surgery is at least equal to conventional fractionation in safety and efficacy; and (2) partial breast RT achieves acceptably low local recurrence rate in selected patients.

Thus, the current key research direction for RT in breast conserving therapy lies in optimising personalised RT in terms of its utilisation, dose fractionation and radiation target volume. The paradigm shift from axillary dissection to sentinel node biopsy and results of multiple recently reported randomised trials have brought focus to the role of regional nodal RT in patients with node-positive early breast cancer. This is an area of significant controversies and active research to identify patients who would benefit from regional RT, including internal mammary nodal irradiation.