Online

ESTRO 2020

Session Item

Poster highlights 19 CL : Breast
8270
Poster Highlights
Clinical
10:46 - 10:54
Radiation and/or endocrine therapy? Recurrence outcomes in low-risk breast cancer patients over 70
Hannah Dahn, Canada
PH-0597

Abstract

Radiation and/or endocrine therapy? Recurrence outcomes in low-risk breast cancer patients over 70
Authors: Hannah DAHN.(Dalhousie University, Department of Radiation Oncology, Halifax, Canada), Jean-Philippe Pignol.(Dalhousie University, Department of Radiation Oncology, Halifax, Canada), Gordon Walsh.(Dalhousie University, Department of Epidemiology, Halifax, Canada), Derek Wilke.(Dalhousie University, Department of Radiation Oncology, Halifax, Canada)
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Purpose or Objective

Women over 70 with early breast cancer treated with breast-conserving surgery are typically offered adjuvant endocrine therapy and radiation therapy. Prior studies have supported the omission of adjuvant radiation in this low-risk population. We sought to compare the effect of adjuvant treatment with endocrine therapy alone, radiation therapy alone or both versus no adjuvant treatment on local control and survival in a population of low-risk breast cancer patients over 70 years of age.

Material and Methods

Following local research ethics board approval, data was extracted on 1,363 low-risk breast cancer patients over the age of 70 treated with a breast-conserving surgery in Nova Scotia from 2003 until 2018. 460 patients met inclusion criteria of T1N0 invasive disease with negative margins and not treated with chemotherapy. The primary outcome was local recurrence-free survival at 5 and 10 years. Secondary outcomes included loco-regional recurrence-free survival, distant metastasis-free survival, disease-free survival and overall survival.

Results

Patients receiving no adjuvant therapy had worse local recurrence-free, loco-regional recurrence-free and disease-free survival than patients receiving at least one form of adjuvant therapy (p < 0.05). 5 year local-recurrence rates were 0.8% in patients receiving both endocrine and radiation therapy, 1.5% in those receiving radiation alone, 4.2% in those receiving endocrine therapy alone and 12% in those receiving no adjuvant therapy. There was no statistically significant difference for patients receiving at least one adjuvant therapy. On multivariate cox proportional hazard analysis, adjuvant endocrine therapy and adjuvant radiation therapy were statistically associated with local recurrence-free survival, while the tumor size, grade, LVI status and margin status were not. No significant difference in distant metastasis-free survival was seen between treatment groups.

Conclusion

This study supports the equivalence of radiation therapy alone, adjuvant endocrine therapy alone and the combination of both in low-risk breast cancer patients over 70 treated with breast-conserving surgery. Receiving no adjuvant therapy is associated with poorer outcomes. As many of these patients are candidates for Accelerated Partial Breast Irradiation, the treatment decision could be between 5 years of endocrine therapy and 5 days of radiotherapy. When deciding about adjuvant therapy in this patient population, patients and clinicians should weigh toxicity and convenience of adjuvant endocrine therapy alone versus adjuvant radiation therapy alone, on a case-by-case basis, to guide treatment decisions.