Breast Cancer

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TU_6_3380 - OncotypeDX Risk Stratification in Early Stage Breast Cancer: When is Accelerated Partial Breast Irradiation (APBI) Safe?

Tuesday, October 23
2:45 PM - 4:15 PM
Location: Innovation Hub, Exhibit Hall 3

OncotypeDX Risk Stratification in Early Stage Breast Cancer: When is Accelerated Partial Breast Irradiation (APBI) Safe?
A. M. Newman1, L. Z. Braunstein2, A. J. Khan3, G. Turashvili1, Y. H. Wen2, E. Zabor1, M. Stempel1, M. Morrow2, and L. Kirstein1; 1Memorial Sloan Kettering Cancer Institute, New York, NY, 2Memorial Sloan Kettering Cancer Center, New York, NY, 3Rutgers Cancer Institute of New Jersey, New Brunswick, NJ

Purpose/Objective(s): Radiation therapy after breast conservation surgery significantly reduces the risk of local recurrence. It is unclear if there is a difference in local recurrence risk in patients who undergo whole breast irradiation vs. APBI. The OncotypeDX Recurrence Score(RS) (TM Genomic Health, Redwood CA) has been shown to be prognostic and predictive for both local and distant recurrence in women with ER+, HER2- breast cancers. The purpose of this study was to determine the relationship between the OncotypeDX RS and short term outcomes in patients undergoing APBI in conjunction with breast conservation therapy (BCT).

Materials/Methods: After IRB approval, patients at a single institution who underwent APBI between 2010-2015 were retrospectively identified. Patients were typically considered for APBI based on the 2009 ASTRO guidelines, and the final decision for radiation approach was based on patient and physician preference. Patients who had OncotypeDX RS were included in our study. During the study period OncotypeDX RS was routinely obtained on ER+, HER2-, node negative patients with tumors between 0.5cm-5cm in size. Data was collected on patient and tumor characteristics, including tumor size, nodal status, hormone receptor status, and Recurrence Score. The OncotypeDX RS categories used were low risk: <18, intermediate risk: 18-30, and high risk: >30. Categorical variables were compared using Fisher’s exact test.

Results: 107 patients were identified, with a mean age of 62 years. All were T1N0, except one patient who was T2N0. Median follow-up time was 3.9 years (range: 0.1 - 7.1). Four patients (3.7%) had high risk, 36 (33.6%) had intermediate risk and 67(62.6%) low risk RS. There were only two ipsilateral in breast recurrences within our cohort, one in the intermediate (at 3 years) and one in the high risk group (at 5 years). Because of the low event rate, a statistical evaluation of the difference in recurrence risk groups could not be performed. Hormone receptor status was the only difference amongst patients of different recurrence scores, with progesterone receptor positivity being more common amongst patients with low and intermediate scores (P<.001).

Conclusion: Our experience reveals a low in-breast recurrence rate among patients with early stage, node negative breast cancer who undergo breast conservation and APBI with a low or intermediate OncotypeDX risk score. These results are reassuring for those patients interested in APBI, who exhibit low or intermediate-risk OncotypeDX RS. More data are needed to characterize the implications of APBI among patients with a high OncotypeDX RS.

Author Disclosure: A.M. Newman: None. L.Z. Braunstein: None. A.J. Khan: Research Grant; Elekta, Cianna Medical. Consultant; Elekta. G. Turashvili: None. Y.H. Wen: None. M. Stempel: None. M. Morrow: board member; Society of Surgical Oncolgy.

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