Abstract PS4-26: Impact of TAILORx data on chemotherapy prescribing in British Columbia
Authors: Tesch Megan , Speers Caroline , Diocee Rekha Manhas , Nichol Alan , Lohrisch Caroline 
Published: February 2021

Background: Developed with retrospective data, the 21-gene recurrence score assay (RS) reduces adjuvant chemotherapy (CTx) use in hormone-positive (HR+), HER2-negative, node-negative breast cancer, justifying the assay’s cost. The TAILORx trial prospectively confirmed the predictive value of RS and established thresholds for CTx benefit in younger and older patients. We examined CTx use in British Columbia (BC) following TAILORx publication, as a prelude to exploring age-adjusted cost effectiveness of the assay.

Methods: We assembled 3 cohorts of patients with HR+, HER2-negative, node-negative breast cancer: diagnosed before RS funding (cohort 1: January 1, 2013-December 31, 2013), after introduction of public funding (cohort 2: July 1, 2015-June 30, 2016), and after TAILORx results (cohort 3: July 1, 2018-June 30, 2019). Patients aged 18-80 years with tumors that were grade 3, grade 2 T1b or larger, or any T size and grade if ≤ 40 years of age were included, matching BC funding criteria. Previous in situ or invasive breast cancer cases were excluded. CTx use by age and RS was compared between cohorts using univariate analyses.

Results: 2,066 patients met inclusion criteria (Table 1). CTx use in cohorts 1, 2, and 3 was 21%, 17%, and 13%, respectively. In cohorts 2 plus 3, CTx use was 30% for patients up to 50 years of age and 11% for patients over 50 years of age. Baseline characteristics were balanced, except grade 3 histology (24%, 25%, 17% in cohorts 1, 2, 3, respectively; p=0.01). RS was ≥ 26 in 33% of grade 3 and 34% of PR negative tumors. CTx use declined by 19% after RS funding was introduced and by another 23% after TAILORx publication (p=0.001). Reduction in CTx use was significant for RS 11-20 tumors (cohort 3 vs. 2, p=0.004). A 7.5% nonsignificant increase in CTx was seen for RS 26-30 tumors (cohort 2 vs. 3, p=0.55). There was no significant change in CTx use in patients aged &gt; 50 years (12% in cohort 2 vs. 10% in cohort 3, p=0.22). Among patients aged 70-80 years in cohort 3 with RS, 5% had RS ≥ 26, and of these, 40% had CTx (9% of patients in this age group), compared with 92% CTx use for patients aged ≤ 50 years with RS ≥ 26 (15% of patients in this age group).

Conclusions: CTx use decreased after TAILORx publication, particularly for RS 11-20 tumors. CTx use changed less in patients over 50 years old, suggesting that trial results confirmed pre-existing prescribing practices. CTx use increased in patients with RS 26-30 tumors, reflecting acceptance of the new threshold for CTx benefit established by TAILORx. CTx use was low overall in patients aged &gt; 50 years, especially in those aged 70-80 years, in part due to the very low frequency of high RS tumors. Given these findings, we conclude that cost effectiveness modelling for publicly funded RS should take age into consideration.

Table 1: Receipt of adjuvant chemotherapy (CTx) by 21-gene recurrence score (RS) result before assay availability (cohort 1), after assay availability (cohort 2), and after TAILORx publication (cohort 3) in patients (pts) aged ≤ 50 (a) and 51-80 years (b).a)Age≤ 50, n = 423Cohort123No. of pts who received CTx / No. of pts in group (%)RS not done51/105 (48.6)28/56 (50)1/6 (16.7)RS ≤ 101/5 (20.0)0/17 (0)1/25 (4.0)RS 11-201/8 (12.5)4/52 (7.7)2/67 (3.0)RS 21-251/3 (33.3)8/17 (47.1)10/20 (50.0)RS 26-300/0 (0)5/5 (100)5/5 (100)RS ≥ 312/2 (100)10/11 (90.9)17/19 (89.5)Entire cohort56/123 (45.5)55/158 (34.8)36/142 (25.4)b)Age51-80, n = 1643Cohort123No. of pts who received CTx / No. of pts in group (%)RS not done72/494 (14.6)25/279 (9.0)2/86 (2.3)RS ≤ 100/6 (0)0/60 (0)0/110 (0)RS 11-202/11 (18.2)5/126 (4.0)0/198 (0)RS 21-252/5 (40.0)6/56 (10.7)2/64 (3.1)RS 26-302/3 (66.7)5/20 (25.0)14/35 (40.0)RS ≥ 312/2 (100)31/40 (77.5)37/48 (77.1)Entire cohort80/521 (15.4)72/581 (12.4)55/541 (10.2)

Citation Format: Megan Tesch, Caroline Speers, Rekha Manhas Diocee, Alan Nichol, Caroline Lohrisch. Impact of TAILORx data on chemotherapy prescribing in British Columbia [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS4-26.