Abstract P4-08-10: MammaPrint identifies 46% of patients, age ≤50 years with oncotype RS 18-30, as low risk and safe to forgo chemotherapy

Abstract

Abstract Background: The PROMIS trial (NCT01617954) previously showed that an OncotypeDx (ODx) Intermediate Recurrence Score (RS 18-30) led to uncertainty in prescribing chemotherapy (CT), especially in the middle of the intermediate range from RS 21-26 where an equal number of patients were recommended to receive and forego CT (Tsai, JAMA Oncology 2018). Forty-seven percent (3183/6711) of randomized TAILORx patients were classified as RS 18-25 and are well represented in PROMIS. These patients with RS 18-25 may still lack definitive CT recommendation following TAILORx, reflexing to age and menopausal status to make a decision. Here, we re-evaluate PROMIS using the subgroup analyses adopted by TAILORx. Methods: MammaPrint (MP) risk of recurrence was determined for ODx intermediate patients by standard diagnostic testing (Agendia, Irvine, CA). Clinical risk was assessed using the MINDACT, modified Adjuvant Online! algorithm (Cardoso, NEJM 2016). The MP high and low risk classification, and patient and tumor characteristics were re-evaluated and subdivided by RS 18-25 vs. RS 26-30. Results: The 840 eligible patients in PROMIS were classified as 61.3% (515/840) clinically low risk and 37.0% (311/840) clinically high risk (including 84 lymph node positive patients). Half (342/684) of all patients with an RS 18-25 and 20.5% (32/156) patients with RS 26-30 were MP low risk. There was no significant difference in the distribution of MP risk in women age ≤50 yrs vs. >50 years (Yates chi-square P=0.62); MP classified 46.4% (84/181) patients age ≤50 yrs and 44.0% (290/659) patients age >50 yrs as low risk. In the clinically-low risk subset of 515 patients, there was also no significant difference in the distribution of MP risk by age (Yates chi-square P=0.89); MP classified 48.3% (56/116) patients age ≤50 yrs and 49.6% (198/399) patients age >50 yrs as low risk. Conclusions: In light of TAILORx and uncertain CT benefit in women ≤50 yrs, MammaPrint provides a definitive high or low risk answer and identifies 46% of these women who may safely forego CT based on MINDACT data. An analysis of young patients in the MINDACT trial showed that MP low risk patients age <45 yrs and 45-55 yrs had very good 5-yr DMFS of 95-98%, in both clinically low and high risk groups (Alders, SABCS 2017). MammaPrint Risk by RS and AgeMammaPrint RiskRS 18-25 RS 26-30 GrandClassification≤50 yrs>50 yrsAll Ages≤50 yrs>50 yrsAll AgesTotalHigh Risk7426834223101124466Low Risk8026234242832374All15453068427129156840 Citation Format: Soliman H, Lo S, Qamar R, Budway R, Levine E, Whitworth P, Mavromatis B, Zon R, Untch S, Treece T, Blumencranz L, Audeh W, Tsai M, PROMIS Investigators Group. MammaPrint identifies 46% of patients, age ≤50 years with oncotype RS 18-30, as low risk and safe to forgo chemotherapy [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P4-08-10.