Genetic Signatures in Women Without Clear Indication of Chemotherapy

Context for Test Request

The American Society of Clinical Oncology recommends that genetic signatures like OncotypeDX and MammaPrint be requested specifically in women without a clear indication of chemotherapy, as these tests demonstrate greater clinical utility in scenarios of clinical uncertainty 1, 2, 3
The National Comprehensive Cancer Network suggests that OncotypeDX should be requested in patients with ER-positive, HER2-negative, lymph node-negative breast cancer, with intermediate risk by clinicopathological criteria, where the decision on chemotherapy is uncertain 4
The European Society for Medical Oncology recommends that MammaPrint should be requested in patients with ER/PgR-positive, HER2-negative, lymph node-negative breast cancer, with high clinical risk by MINDACT categorization 1, 2, 3

The American College of Physicians found that the evidence for OncotypeDX comes from retrospective analyses of prospective trials, showing that the benefit of chemotherapy in ER-positive, lymph node-negative patients was more convincing in the high-risk category (reduction of 27% in 10-year recurrence rate) 5, 6
The European Society for Medical Oncology states that MammaPrint can identify patients with high clinical risk but low genomic risk who had a relatively favorable prognosis in the absence of adjuvant chemotherapy, based on the prospective randomized MINDACT study 1, 2, 3

The American Society of Clinical Oncology notes that three-quarters of OncotypeDX results fall into the intermediate and low-risk categories, where the confidence intervals of recurrence risk estimates are wide and overlapping, and the evidence for chemotherapy benefit is inadequate 5, 6
The National Comprehensive Cancer Network advises that MammaPrint should be used with caution in patients with 2-3 positive lymph nodes due to the relatively limited number of these patients in the MINDACT study 1, 7

The European Society for Medical Oncology recommends not requesting multiple tests, as there are no data suggesting that this is useful for guiding treatment decisions 3
The American College of Physicians states that the IMPAKT 2012 working group concluded that it was unclear from current evidence whether modifying treatment decisions based on genomic test results would result in improved clinical outcomes, and did not endorse omitting chemotherapy in patients with ER-positive breast cancer solely based on low risk by genomic testing 8, 4

The American Society of Clinical Oncology recommends MammaPrint and OncotypeDX for prognostic value and clinical utility in ER-positive, HER2-negative, lymph node-negative breast cancer, with Level I, Grade A evidence, but MammaPrint has the advantage of being validated across all ER subtypes 9, 10, 11
MammaPrint is applicable to both ER-positive AND ER-negative breast cancer, making it the only validated test for triple-negative disease among major genomic assays, intended for women ≤61 years with Stage I-II, lymph node-negative breast cancer with tumors ≤5 cm 9, 10
OncotypeDX is exclusively designed for ER-positive, HER2-negative breast cancer, and works on formalin-fixed, paraffin-embedded tissue, providing a continuous Recurrence Score (0-100) 11, 12, 13

MammaPrint achieved [I, A] level evidence through the prospective randomized MINDACT trial, demonstrating that women with clinically high-risk but genomically low-risk disease could safely avoid chemotherapy, with validation in both node-negative and node-positive cancers within the MINDACT study 9, 14
OncotypeDX achieved [I, A] level evidence through the prospective TAILORx and Plan B trials for node-negative disease, and the RxPONDER trial (SWOG 1007) evaluated utility in node-positive disease 9, 12, 13
The EGAPP Working Group confirmed adequate clinical validity for OncotypeDX but noted insufficient direct evidence that testing improves clinical outcomes 12, 13

Both MammaPrint and OncotypeDX reliably prognosticate distant recurrence risk in ER-positive, node-negative disease, with MammaPrint identifying ultra-low risk patients with excellent 10-20 year survival 9
OncotypeDX has stronger evidence for predicting chemotherapy benefit, particularly with CMF regimens, based on prospective-retrospective analyses 15, 12
The American College of Surgeons recommends considering both tests for reducing decisional uncertainty and anxiety in patients with breast cancer 14

Both tests have 86-100% probability of being cost-effective at willingness-to-pay thresholds of $50,000 per QALY, with OncotypeDX likely being cost-effective compared to MammaPrint in head-to-head comparisons 9
The OPTIMA Prelim Trial showed 86% probability of molecular testing being cost-effective 9