Abstract CT271: PRECISION (Profiling early breast cancer for radiotherapy omission): A phase II study of breast-conserving surgery without adjuvant radiotherapy for favorable-risk breast cancer
Authors: Patel Mira A. , Dillon Deborah A. , Digiovanni Giulia , Chen Yu-Hui , Catalano Paul , Perez Carmen , Wazer David , Wright Jean , Jimenez Rachel , Winer Eric , Wong Julia , Bellon Jennifer , Braunstein Lior Z. 
Published: September 2020

Background: Radiation therapy (RT) following breast conserving surgery (BCS) is known to improve locoregional and distant control in women with invasive breast cancer; however, RT does pose significant cost and potential risk, including concern for cardiopulmonary toxicity and secondary malignancy. Randomized trials show that the omission of RT among older women with otherwise favorable-risk breast cancer does not affect overall survival (OS) at 10 years, and modestly increases the risk of local recurrence (LR). Nevertheless, there is little prospective support for RT omission in younger women. Moreover, risk stratification in the randomized prospective studies to date relies on limited methods with potentially low fidelity at distinguishing luminal subtypes. Enhanced molecular profiling techniques could better discern tumor biology and, in turn, more precisely assess risk. PAM-50 is an expression profile of 50 genes used to classify breast cancer intrinsic subtype with consequent prognostic implications. The goal of this study is to identify low-risk breast cancer patients with luminal A subtype who may feasibly omit RT from their therapeutic regimen. Methods: This is a phase II prospective cohort study (NCT02653755) designed to assess the safety of treatment de-escalation (omission of RT) in women with favorable-risk invasive breast cancer following BCS. Eligibility criteria include female patients with invasive breast cancer, age 50-75, with tumors less than or equal to 2cm, negative surgical margins, ER+ or PR+ and HER2- disease, grade 1 or 2, no lymph node involvement, and no plans for chemotherapy or biologic therapy, who are eligible for and willing to receive endocrine therapy. Tumor samples from eligible patients will undergo PAM-50 transcriptional profiling using the Nanostring Prosigna assay. A low Risk of Recurrence (ROR) score, corresponding to the luminal A subtype, will permit patients to forego radiotherapy should they so choose. The primary endpoint is 5-year risk of local or regional recurrence of invasive or in situ breast carcinoma within the ipsilateral breast or regional lymph nodes. Study enrollment began in May 2016.

Citation Format: Mira A. Patel, Deborah A. Dillon, Giulia Digiovanni, Yu-Hui Chen, Paul Catalano, Carmen Perez, David Wazer, Jean Wright, Rachel Jimenez, Eric Winer, Julia Wong, Jennifer Bellon, Lior Z. Braunstein. PRECISION (Profiling early breast cancer for radiotherapy omission): A phase II study of breast-conserving surgery without adjuvant radiotherapy for favorable-risk breast cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr CT271.