21-Gene Recurrence Score Assay Use Appropriate, Equitable in Older Breast Cancer Patients

Adoption of the 21-gene recurrence score test to guide breast cancer treatment in older women is consistent with guidelines and ‘relatively homogeneous’

medwireNews: US researchers find that use of the Oncotype DX 21-Gene recurrence score (RS) assay, which can help to guide adjuvant chemotherapy decisions in women with breast cancer, is in accordance with guidelines and equitable across geographical regions and racial groups.

The US Centers for Medicare & Medicaid Services approved coverage of the test in women with stage I or II, Oestrogen receptor (ER)-positive, lymph node (LN)-negative breast cancer in 2006, since when it has been “adopted quickly” in clinical practice, say the researchers in JAMA Oncology.

Overall, in the 70,802 breast cancer patients aged 66 years or older who were identified from the Surveillance, Epidemiology, and End Results–Medicare linked dataset, the use of the RS assay increased from 1.1% in 2005 to 10.1% in 2009.

The majority of tests (60.9%) were performed in women with intermediate-risk disease (ie, invasive, ER-positive, LN-negative tumours >1 cm), which, the team explains, is the population for whom the test is recommended as per previous studies and the American Society of Clinical Oncology guidelines.

Of the 1442 tests in patients without intermediate-risk disease, 47.5% had T1b and 26.8% had N1 disease, and as such had “borderline indications for testing”, which suggests that “testing was largely consistent with guidelines and clinical practice recommendations”.

Multivariable analysis of data from the 18,128 intermediate-risk patients showed that women aged over 70 years had a significantly lower likelihood of receiving the RS assay than those in the 66 to 70 years age bracket.

Patients with multiple comorbidities were also significantly less likely to be tested compared with women lacking comorbid conditions, at an odds ratio (OR) of 0.64, as were those with progesterone receptor-positive tumours compared with receptor-negative tumours, at an OR of 0.82.

But being married, having tumours larger than 2 cm and living in the Northeast of the USA compared with the West significantly increased the odds of receiving the test, with ORs of 1.19, 1.29 and 1.83, respectively. This was also the case for women with tumours of histological grade G2 or G3 compared with G1 disease, with ORs of 1.39 and 1.28, respectively.

Researcher Michaela Dinan, from Duke University School of Medicine, Durham, North Carolina, and co-workers, did not find a correlation between test use and race. Nor was there a significant association with education level, socioeconomic status, urban location or tumour histology.

Interestingly, rates of chemotherapy use were comparable between 2005 and 2009, both in the overall study population and in the subgroup of women with intermediate-risk disease.

Writing in an accompanying commentary, Lisa Flaum and William Gradishar, from Northwestern University in Chicago, Illinois, USA, observe: “If the use of the RS assay is not altering treatment recommendations in the older patient population, it would be interesting to document whether this is related to tumor characteristics, physician bias, or patient preference.”

They conclude: “A prospective study of physician and patient decision-making in this patient age group would also be useful in answering some of these questions.”

References

Dinan MA, Mi X, Reed SD, et al. Initial Trends in the Use of the 21-Gene Recurrence Score Assay for Patients With Breast Cancer in the Medicare Population, 2005-2009. JAMA Oncol 2015; Advance online publication 5 March. doi:10.1001/jamaoncol.2015.43

Flaum L, Gradishar WJ. Refining Treatment Decisions in Older Patients With Breast Cancer. JAMA Oncol 2015; Advance online publication 5 March. doi:10.1001/jamaoncol.2015.32

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