Abstract P4-08-04: The clinical utility of oncotype Dx for patients with recurrence scores of 10 or less: A value based pathology study of tumor histopathology and outcomes analysis in an integrated delivery and finance health system

Introduction The majority of publications regarding breast cancer GEPTs rarely supply detailed breast tumor histopathology in their outcome studies. As a result, the cost effective role of clinical risk assessment with histopathology of breast carcinomas tends to be minimized. The aims of this study are to characterize the details of breast tumor histopathology of patients with Oncotype Dx Recurrence Scores (RS) of 10 or less, and determine if Oncotype Dx offers value and clinical utility for patients with these low grade tumors Methods A total of 459 patients (18%) with Oncotype Dx RS of 10 or less were retrieved from a registry of 2558 patients with Oncotype Dx results. Patients had five years of follow-up with tumor registry and were treated with endocrine therapy alone. Tissue slides were available to review on 441/459 patients. Recorded details included (1) histopathologic type of carcinoma (2) mitotic score (MS), tubule formation, nuclear pleomorphism and Notttingham histologc (NG) grade. (3) Estrogen (ER) and progesterone (PgR) semiquantitated by Allred Score and Histologic Score (H Score: strong 200-300, moderate 100-199, weak Results Patient ages were 33-92, with mean/median age of 60, and all had endocrine therapy alone. 148 of 441(34%) patients had carcinomas of “special types”, notable for low grade/good prognosis including tubular 22(15%), cribriform 15 (10.1%), papillary 17 (11.5%), and mucinous 28 (21%), along with 63 (42.5%) low grade classic lobular carcinomas and 3 (2%) low grade mixed ductal and lobular carcinomas. All 148 tumors had a MS of 1, were NG1 and had high ER HScores (280 median/263 mean) (Allred Scores 7-8) and high PR HScores (210 median/201 mean) (Allred Scores 6-8). The remaining 293 tumors were ductal carcinomas of no special type (NST), and 261/293 (89%) of these had a MS of 1/NG2. Of the remaining cases, 10 (3%) had a MS of 2/NG2, 18 (6%) had MS of 2/NG3 and four (1%) were MS3/NG3. Estrogen receptor H Score/Allred Score was strong (Allred Score 7-8) in 395/441 (89.6%), moderate in 45 (10.2%) and weak in 1 patient (0.2%). Progesterone HScores were strong in (Allred Score 6-8) 269/441 (76%) and moderate in the remainder. Strong and moderate ER comprised 99.8% of tumors. Thus, tumors with MS1, and NG1, all with ER HScore >200 (Allred Score of 7-8) were enriched in the RS At 5 years, 433 patients (98%) were alive, 8 were dead, 1 from breast cancer due to distant recurrence. The 5-year breast cancer specific survival for this group was 99.7%. [95%CI 98.5-99.9.] 87 cases were accrued in the ongoing prospective study to date. There were 15/87 (17%) cases, 95% of which were correctly identified by pathologists as having an RS 22. Conclusions Pathologists can identify these low risk tumors with high accuracy. Oncotype Dx lacks clinical value and utility in this setting. Citation Format: Dabbs DJ, Serdy K, Onisko A, Clark BZ, Bhargava R, Smalley S, Perkins S, Brufsky AM. The clinical utility of oncotype Dx for patients with recurrence scores of 10 or less: A value based pathology study of tumor histopathology and outcomes analysis in an integrated delivery and finance health system [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P4-08-04.