Abstract P3-08-56: The impact of the 21 gene recurrence score (RS) on chemotherapy prescribing in estrogen receptor positive (ER+), lymph node positive (LN+) breast cancer (BC) in Ireland: A national, multi-centre, prospective study
Authors: Mullally William J , Bracken-Clarke Dara , Padmore Andrew , O'Reilly Seamus , O’Mahony Deirdre , Walshe Janice , Kennedy John , Gupta Rajnish , Kelly Cathy , O'Connor Miriam , Duffy Karen , Keane Maccon , Hennessy Bryan T , Morris Patrick G 
Published: March 2020

Background: The 21 gene recurrence score (OncotypeDx ®) is reimbursed in Ireland to guide adjuvant treatment decisions for ER+, LN-negative, human epidermal growth factor receptor 2 (HER2)-negative BC. There is emerging evidence supporting the clinical utility of this test in patients with LN+ disease. Although the exact cut-off for chemotherapy has not been defined in this population, SEER data support the omission of chemotherapy for patients with RS &lt;18 and the WSG Plan B randomised prospective study suggested excellent 5- year outcomes in patients with RS ≤11 treated with hormone therapy alone. However, the RS has not yet been reimbursed for patients with LN+ disease in Ireland. Methods: The Oncotype DX Breast Recurrence Score test N+ Access Programme (PONDx) aimed to collect real-life data on the use of the 21 gene RS in patients with LN+ ER+, HER2- early stage breast cancer. The PONDx study was conducted between March 2018 and May 2019 across the national oncology centres to determine the extent to which use of the RS could alter chemotherapy recommendations. Eligible patients had 1-3 LN+, HR+ and HER2- BC and were deemed possible candidates for chemotherapy. Anonymous questionnaires were completed by a Consultant Oncologist after the RS test was available. Data on patient demographics, tumour characteristics and treatment recommendations were collected.

Results: In total, 294 patients were enrolled across the - nine centres. Complete data is available on 123 patients (range 38 to 75, median 54 years), which included two male patients. Of the remaining 121 (98%) patients, 49 (40%) were premenopausal, 26 (21%) perimenopausal and 46 (37%) postmenopausal. The median tumour size was 38 mm (Range 7 to 58 mm). There were 101 (82%) patients with invasive ductal carcinoma, 17 (14%) with lobular carcinoma and 5 (4%) classified as other breast histology. Seventeen patients (14%) had grade 1, 74 (60%) grade 2 and 32 (26%) grade 3 disease. There were 79 (64%) patients with 1 LN+, 35 (29%) with 2 LN+ and 9 (7%) with 3 LN+ status. Overall access to the 21 gene RS test led to a 32% reduction in chemotherapy, 112 (91%) to 72 (59%) patients. This was most notable in patients with ductal histology (91 vs 61) and grade 2 breast cancer (66 vs 41) representing a 24.4% and 20.3% reduction, respectively. Similarly patients with 1 LN+ (71 vs 46) and 2 LN+ (34 vs 21) represented a 20.3% and 9.7% reduction, respectively. This study also identified four patients aged less than 40, for whom chemotherapy was not recommended. The biggest reduction in chemotherapy occurred in women aged over 50 (62 vs 36) at 21.1%. Overall, in 65% of cases, medical oncologists deemed the RS test result significantly changed treatment recommendations. Conclusion: These findings are consistent with results from similar studies in other countries. Broader access to the 21-gene RS could result in a reduction in the use of chemotherapy in Ireland.

Citation Format: William J Mullally, Dara Bracken-Clarke, Andrew Padmore, Seamus O'Reilly, Deirdre O’Mahony, Janice Walshe, John Kennedy, Rajnish Gupta, Cathy Kelly, Miriam O'Connor, Karen Duffy, Maccon Keane, Bryan T Hennessy, Patrick G Morris. The impact of the 21 gene recurrence score (RS) on chemotherapy prescribing in estrogen receptor positive (ER+), lymph node positive (LN+) breast cancer (BC) in Ireland: A national, multi-centre, prospective study [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-08-56.