STARS Breast Trial (Study of Anastrozole and Radiotherapy Sequencing Pilot)

Adjuvant radiotherapy is well established as the primary modality to enhance local control in breast cancer. The use of adjuvant hormone therapy such as tamoxifen has shown to improve local control to a relatively minor amount on its own and does enhance local control of adjuvant radiotherapy. There is however, conflicting in vitro and clinical data regarding the effects of different sequences on tamoxifen and radiotherapy in terms of both local control and enhancement of radiotherapy toxicities. Aromatase inhibitors such as anastrazole are establishing themselves as a class of drug superior to tamoxifen for the control of estrogen dependent breast cancers and overall are better tolerated with the exception of greater bone loss. As the key question is whether the sequencing of the aromatase inhibitor anastrozole alters local control by acting as an enhancer of the radiation breast cancer cell kill, it is therefore the aim of this study to compare 3 months of anastrozole prior to radiotherapy versus 3 months of anastrozole after radiotherapy with a specific objective of reducing the baseline ratio of in- field radiotherapy failure from 6% to 3%.This pilot study is preliminary to a planned long term study to investigate local failure. For the pilot a period of 6 months with all contributing centres open will provide a good test of recruitment matching estimates. 100 patients will provide a good sample to compare to the 270 tamoxifen treated women in the breast boost study for quality of life. It will also provide a 95% CI on the proportion of complying women in the order of ± 5% if 85 to 90 % of women comply.