S318
Clinical - Breast
ESTRO 2026
significant. In-field failure rates overall are lower than predicted despite recruiting the predicted risk profile. In the initial 3 month sequencing study period there were 5 SAEs in each group. Conclusion: The recruited risk profile matched that predicted but local failure rate was lower. There was no signal of inhibition of local control for anastrozole commenced first and the non-statistically significant hazard ratio point estimate is close to that modelled. TROG STARS 08.06 recruited 2023 patients, is in follow-up and likely to report in 2027. References: 1 Graham PH, Fang ZM, Clarke RA. Pre-treatment with anastrozole maybe the optimal treatment sequence with radiotherapy for breast cancer. Asia Pacific J Clin Oncol 2008; 4:27-332 Bourgier C, Kernes S Gourgou S et al. Concurrent or sequential letrozole with adjuvant breast radiotherapy: final results of the CO-HO-RT phase II randomised trial. Annals of Oncology 2016; 27: 747-4803 McGee SE, Clemons M, Pond G et al A randomized trial comparing concurrent versus sequential radiation and endocrine therapy in early- stage hormone responsive breast cancer Current Oncology 2024; 31: 4531-4545. Keywords: Aromatase inhibition sequencing Eliminating surgery for breast cancers with an exceptional response to ablative radiotherapy: phase 2 trial primary endpoints Simona F Shaitelman 1 , Savitri Krishnamurthy 2 , Yan H Lin 3 , Yu Shen 3 , Gaiane M Rauch 4 , Vicente Valero 5 , Manickam Muruganandham 6 , Benjamin D Smith 1 , Melissa P Mitchell 1 , Karen E Hoffman 1 , Chelain R Goodman 1 , Wendy A Woodward 1 , Henry M Kuerer 7 1 Breast Radiation Oncology, UT MD Anderson Cancer Center, Houston, USA. 2 Anatomical Pathology, UT MD Anderson Cancer Center, Houston, USA. 3 Biostatistics, UT MD Anderson Cancer Center, Houston, USA. 4 Abdominal Imaging, UT MD Anderson Cancer Center, Houston, USA. 5 Breast Medical Oncology, UT MD Anderson Cancer Center, Houston, USA. 6 Radiation Physics, UT MD Anderson Cancer Center, Houston, USA. 7 Breast Surgical Oncology, UT MD Anderson Cancer Center, Houston, USA Purpose/Objective: To report co-primary endpoints of pathologic complete response (pCR) and 3-year progression free survival (PFS) in a prospective, phase II trial (NCT02945579) of definitive, ablative radiotherapy (ART) with endocrine therapy (ET) and omission of surgery. Proffered Paper 4177
Proffered Paper 4160
STARS Pilot Randomised Study of Anastrozole and radiotherapy sequencing for adjuvant treatment of breast cancer NCT00126360 10 year results Peter Henry Graham 1,2 , George Papadatos 3 , Jodi Lynch 1,2 , Helen Cox 1 , Lois Browne 1 1 Cancer Care Centre, St George Public Hospital, Kogarah, Australia. 2 Medicine, University of New South Wales, Randwick, Australia. 3 Cancer Centre, Campbelltown Hospital, Campbelltown, Australia Purpose/Objective: Optimum endocrine therapy sequencing with radiotherapy is controversial. In vitro aromatase inhibition sensitizes breast cancer cells1. There is randomised sequencing clinical data only for tolerance with letrozole (N=150) and/or tamoxifen (N=260) and none powered to test efficacy2,3.This pilot prefaced Trans Tasman Radiation Oncology Group 08.06 STARS trial to demonstrate multicentre recruitment feasibility and cohort risk profile to validate the larger trial design whose primary endpoint is in-field local control with a predicted estimated 10 year in-field failure rate of 6% in the control arm and a hazard ratio for failure of 0.5 for the test arm of anastrozole first. Material/Methods: Eligible patients were ATAC criteria post-menopausal, had clear margins after mastectomy or breast conservation, oestrogen receptor positive, ECOG performance status <3 and prescribed adjuvant radiotherapy dose BED Gy4 ≥ 65. Patients were randomised to commence an initial 3 month anastrozole course within a week of randomisation and at least 3 weeks prior to radiotherapy continued concurrently and subsequently or to commence anastrozole following completion of radiotherapy. Patients were stratified by chemotherapy, mastectomy versus conservation, use of boost if conservation and planned long term endocrine therapy anastrozole or tamoxifen/nil. Results: From August 2005 to September 2011 4 centres recruited 386 patients (193 in each arm). Mean age was 60 (40 to 85) years. Chemotherapy was given to
46%, long term anastrozole to 92%, breast conservation in 82% of whom 41% received a
radiotherapy boost, approximating the anticipated profile. Planned dose (pre-boost) was 50 Gy in 25 fractions for 75% and 42.4 Gy in 16 fractions for 32%. The supraclavicular fossa was treated in 21%, the axilla and internal mammary chain in 5%. Infield failure after 10 years was anastrozole first 2.3% (0.9 to 5.9%) versus radiotherapy first 3.5% (1.6 – 7.7%) HR 0.55 p=0.34. Overall survival at 10 years was 92.9% (88.1 – 95.8%) versus 86.2 (80.3 – 90.5%) HR 0.63 p=0.14. As anticipated in this pilot neither are statistically
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