A recent systematic review and meta-analysis was performed to compare responses to neoadjuvant endocrine therapy (NET) in patients with estrogen receptor-positive, human epidermal growth factor receptor-negative (ER+/HER2-) breast cancer (BC) following stratification by recurrence score (RS) testing. The investigators hypothesized that the RS might determine patients who are more likely to respond to and undergo breast-conservation surgery (BCS) following NET.

The systematic review and meta-analysis was performed using the PubMed Medline, EMBASE, and Scopus databases utilizing the according to PRISMA and MOOSE guidelines. The population, intervention, comparison and outcomes (PICO) framework was followed. Women aged >18 years with newly diagnosed ER + BC without distant metastatic disease who received NET following preoperative RS testing were included in the study. RS scores were categorized as low, intermediate-to-high, low-to-intermediate, or high.

Primary outcomes included pathological complete response (pCR), which was defined as the absence of residual tumor cells in resected specimens following NET; partial response (PR), which referred to a reduction in degree of residual tumor cells in resected specimens following NET; or successful conversion of BCS following completion of NET. Secondary outcomes included disease progression (DP), which was described as increased tumor size on clinical or radiological examination following NET; stable disease (SD), which was defined as no change in tumor size on clinical examination following completion of NET; or 5-year disease-free survival, which was considered freedom from disease recurrence or death at 60-month follow-up following cancer resection.

Based on data in the quantitative analysis, the mean age of the study population was 62.6 years; 78.4% of patients were postmenopausal at diagnosis. NET consisted of fulvestrant, anastrozole, exemestane, letrozole, goserelin, and tamoxifen. NET was prescribed for a mean duration of 20.0 months. The mean RS score was 14.5, with four studies breaking down risk as RS <18 being low, RS 18-30 being intermediate, and RS >30 being high risk. Four other studies considered low risk to be an RS <11, intermediate risk as RS 11-25, and high risk as RS >25.

A total of 691 patients were included in the analysis. Of these patients, 37.2% had a low RS, 36.5% had an intermediate RS, and 16.6% had a high RS.

For patients with an RS <25 and <30, the odds ratios were 4.60 and 3.40, respectively (P <.0001), for achieving PR to NET. RS failed to predict both SD and DP following NET. For patients undergoing BCS, an RS <18 was associated with BCS following NET, but was not associated with BCS conversion rates. For those with an RS >30, NET was not associated with either BCS or increased BCS conversion rates. Lower risk scores (RS <18) were associated with significantly less disease recurrence than higher scores (RS >18). Unfortunately, RS >30 was associated with a 4.07-fold increase in disease recurrence compared with RS <30.

The investigators concluded that patients with low or intermediate RS were four times more likely to achieve a response to NET than those with high-risk scores. In patients with low-intermediate RS, there were comparable rates of pCR following either NET or neoadjuvant chemotherapy (NAC), suggesting that these patients should either receive NET or proceed directly to surgery and may be able to forego NAC. During the COVID-19 pandemic, surgical interventions have not always been readily available. In this case, NET has been used as a "bridging" strategy to surgery for patients with early ER+ disease.

Pharmacists managing patients with BC should be cognizant of the role that Oncotype DX RS can have in determining BC treatment and avoiding unnecessary chemotherapy.

The content contained in this article is for informational purposes only. The content is not intended to be a substitute for professional advice. Reliance on any information provided in this article is solely at your own risk.

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