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Recurrence score assay driving chemo decisions in unexpected ways

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Crucial information missing

The study by Dinan et al. adds a valuable population-based lens to our knowledge of RS adoption and chemotherapy use because prior utilization studies have been more limited in scope. However, many crucial details are missing from this bird’s-eye view.

Most critical are: (1) the exclusion of women younger than 65 years, who make up the majority of breast cancer patients; (2) the lack of RS assay results, which markedly limits evaluation of its impact on chemotherapy decision making; and (3) the absence of patient and physician perspectives, without which we cannot fully understand how use of the RS assay informs treatment choices. Only 14% of patients in this study received chemotherapy, compared with 40%-50% in studies with wider age ranges; this substantial difference in systemic therapy use suggests that the RS assay use patterns observed here may not generalize to younger women.

Getting “under the hood” of such complex medical decision making requires supplementing registry data not only with genomic test results but also with measures of the patient and physician experience. We still do not know why and under what circumstances physicians choose to order an RS assay; to what extent physicians’ treatment recommendations follow RS assay results; and what role, if any, patients play in the choice to order an RS assay and in subsequent chemotherapy decisions. Ultimately, we cannot assess the effects of RS assay use on breast cancer treatment without a deeper understanding of patients’ and physicians’ perspectives.

These comments were excerpted from an editorial accompanying the report by Dr. Dinan and her associates (JAMA Oncol. 2015. doi: 10.1001/jamaoncol.2015.2719).

Dr. Allison Kurian is an assistant professor of medicine (oncology) and of health research and policy at Stanford (Calif.) University Medical Center. Christopher Friese, Ph.D., R.N., is an assistant professor at the School of Nursing, University of Michigan, Ann Arbor.


 

FROM JAMA ONCOLOGY

References

Adoption of the 21-gene recurrence score (RS) assay does not appear to have decreased chemotherapy use overall among Medicare beneficiaries diagnosed with breast cancer, investigators reported online in JAMA Oncology. However, use of the assay was associated with decreased chemotherapy use in high-risk patients and increased chemotherapy use in low-risk patients in the retrospective study.

“Contrary to our hypothesis, we did not observe a change in chemotherapy use in the overall study population after the adoption of the RS assay between 2005 and 2009 or a general association between receipt of chemotherapy and use of the assay in multivariable analyses or HRR [hospital referral region]–level analyses,” Dr. Michaela Dinan of the Duke Clinical Research Institute and her associates wrote (JAMA Oncol. doi: 10.1001/jamaoncol.2015.2722).

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There was, however, an interaction between use of the Oncotype DX recurrence score (RS) assay and National Comprehensive Cancer Network (NCCN) risk category.

RS use was associated with lower chemotherapy use in women with high-risk disease (odds ratio, 0.34; 99% confidence interval, 0.20-0.57) and higher chemotherapy use in those with low-risk disease (OR, 4.46; 99% CI, 3.15-6.31).

NCCN guidelines recommend considering chemotherapy in estrogen receptor (ER)-positive, node-negative breast cancer for all but the smallest tumors.

The 21-gene Oncotype DX assay was one of the first gene expression profile tests to reach the market, and studies have suggested its use could save money by guiding allocation of chemotherapy to patients most likely to benefit.

An earlier multicenter NCCN database analysis reported an association between the progressive rise in RS testing and an overall decline in adjuvant chemotherapy in hormone-receptive breast cancers diagnosed between 2006 and 2008.

The current study took a wider look at use of the RS assay and chemotherapy using a nationally representative sample of 44,044 women, aged 65 years and older, diagnosed with early-stage, ER-positive breast cancer between 2005 and 2009 in the SEER (Surveillance, Epidemiology, and End Results) database linked with Medicare claims. Of these, 24% had low-risk, 51.3% intermediate-risk, and 24.6% high-risk disease based on NCCN criteria. Roughly a quarter were node positive.

Use of the RS assay was higher among patients 70 years or younger, patients with fewer comorbid conditions, and patients with T1c tumors, node-negative disease, and intermediate-risk disease, Dr. Dinan and associates reported.

In all, 14.3% of patients overall and 26.5% of patients 70 years or younger received chemotherapy within 12 months of diagnosis, “which supports a significant influence of age on chemotherapy use,” they said.

“Our data suggest that use of the RS assay may have decreased chemotherapy use in general practice among younger patients with high-risk disease in whom receipt of chemotherapy would have otherwise been likely but that it was associated with greater chemotherapy use in patients with low-risk disease. The impact of the RS assay on chemotherapy use is likely population dependent and is influenced by the population’s pretest likelihood of undergoing chemotherapy,” they concluded.

The authors acknowledge that the study had limitations as only RS assays paid for by Medicare were analyzed, HER2 status was unavailable, and patients in the SEER registry are more likely to be nonwhite and live in high-poverty and urban areas, which may affect generalizability.

The study was sponsored by a grant from the Agency for Healthcare Research and Quality. The authors reported having no conflicts of interests. Dr. Kurian and Dr. Friese reported receiving funding from a National Cancer Institute grant to the University of Michigan.

pwendling@frontlinemedcom.com

On Twitter @pwendl

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