Breast cancer multigene testing trends and impact on chemotherapy use.
A 21-gene test that predicts recurrence risk among women with hormone receptor positive (HR+), localized breast cancer was nationally recommended in 2007, but we know little about its subsequent impact. We evaluated: a) patient characteristics associated with test use, b) correlations between Recurrence Score (RS) and chemotherapy, and c) whether test introduction was associated with a reduction in chemotherapy use.



Retrospective cohort study.



The Kaiser Permanente Northern California tumor registry and electronic health records from 2005 to 2012 were used to identify HR+, human epidermal growth factor receptor 2 negative, node-negative cancers. Analyses used logistic regression with propensity score matching and 2-level logistic regression.



Of the 7004 patients who met guidelines for testing, 22% were tested and 26% had chemotherapy. Test use was more likely in younger women (for ages 40-49 years vs 50-64 years: odds ratio [OR], 1.22; 95% CI, 1.04-1.44), in women with tumors sized 1.0 to 2.0 cm versus > 2 cm (OR, 1.20; 95% CI, 1.03-1.40), and in women from higher-income neighborhoods (for each $10,000 increase in area median income: OR, 1.05; 95% CI, 1.03-1.07). Among patients with low RS, 8% had chemotherapy versus 72% among patients with high RS (P < .01). In propensity score-matched analyses, testing was associated with an absolute reduction of 6.2% in the proportion of women receiving chemotherapy (95% CI, 2.9%-9.5%); the 2-level model showed a similar but nonsignificant (P = .14) association.



The 21-gene test is used in a minority of eligible patients in this integrated plan. Its use appears to be associated with a modest decrease in overall chemotherapy use.
Division of Research, Kaiser Permanente, 2000 Broadway, Oakland, CA 94612. E-mail: tom.ray@kp.org.
G Thomas
GT
Ray
Jeanne
J
Mandelblatt
Laurel A
LA
Habel
Scott
S
Ramsey
Lawrence H
LH
Kushi
Yan
Y
Li
Tracy A
TA
Lieu
D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D014408:Biomarkers, Tumor / Q000235:genetics*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000235:genetics*; D002140:California; D015331:Cohort Studies; D005260:Female; D020869:Gene Expression Profiling; D005820:Genetic Testing; D006801:Humans; D008875:Middle Aged; D005810:Multigene Family; D009364:Neoplasm Recurrence, Local / Q000188:drug therapy* / Q000235:genetics*; D016017:Odds Ratio; D011960:Receptors, Estrogen / Q000235:genetics*; D012189:Retrospective Studies
D014408:Biomarkers, Tumor; D011960:Receptors, Estrogen