Should an Oncotype DX (Genomic Health test) be done in a postmenopausal patient with T1cN0, ER (Estrogen Receptor) positive, PR (Progesterone Receptor) positive, and HER2 (Human Epidermal growth factor Receptor 2) negative breast cancer who underwent bilateral simple mastectomy?

Oncotype DX Testing in Post-Mastectomy ER/PR Positive, HER2 Negative Breast Cancer

Oncotype DX testing is not recommended for this 63-year-old postmenopausal patient with T1cN0, ER/PR positive, HER2 negative breast cancer who has already undergone bilateral simple mastectomy. 1

Rationale for Not Performing Oncotype DX Testing

• The primary purpose of Oncotype DX testing is to guide decisions about adjuvant chemotherapy in addition to endocrine therapy in patients with early-stage, hormone receptor-positive, HER2-negative breast cancer 1
• In patients who have undergone mastectomy for small (T1c) node-negative tumors, the absolute benefit of adding chemotherapy is already known to be small, making the test less clinically useful in this setting 1
• The NCCN guidelines specifically recommend considering the 21-gene assay (Oncotype DX) for patients who are candidates for chemotherapy, which may not apply to this post-mastectomy patient with favorable tumor characteristics 1

Understanding the Role of Oncotype DX

Oncotype DX provides a Recurrence Score (RS) that stratifies patients into risk categories:

• Low risk (RS 0-10): Very low risk of distant recurrence with endocrine therapy alone 1
• Intermediate risk (RS 11-25): Limited additional benefit from chemotherapy in postmenopausal women 1
• High risk (RS ≥31): Clear benefit from adjuvant chemotherapy 1

Factors That Already Suggest Low Risk in This Patient

• T1c (>0.5-2.0 cm), node-negative tumor status suggests relatively favorable prognosis 1
• ER and PR positivity indicates likely good response to endocrine therapy alone 1
• HER2 negative status eliminates need for anti-HER2 targeted therapy 1
• Postmenopausal status (age 63) is associated with less aggressive disease biology in hormone-positive tumors 1
• Bilateral mastectomy has already significantly reduced the risk of local recurrence 1

When Oncotype DX Would Be Appropriate

Oncotype DX testing would be more valuable in the following scenarios:

• When the patient has not yet undergone definitive surgery and treatment decisions are still pending 1
• In cases with conflicting clinicopathological features where the benefit of chemotherapy is uncertain 1
• For patients with 1-3 positive lymph nodes where the benefit of chemotherapy is questionable 1

Alternative Approaches to Risk Assessment

• Standard clinicopathological features can provide substantial prognostic information without the need for genomic testing 2, 3
• Studies have shown that histopathological variables like nuclear grade, mitotic count, and PR status can predict Oncotype DX recurrence scores with reasonable accuracy 2, 4
• Low-grade invasive carcinomas with favorable histology rarely have high-risk recurrence scores 5

Conclusion for Clinical Practice

For this postmenopausal patient with T1cN0, ER/PR positive, HER2 negative breast cancer who has already undergone bilateral mastectomy, standard endocrine therapy is likely sufficient without the need for Oncotype DX testing to determine chemotherapy benefit 1. The clinical utility of the test in this post-surgical setting is limited, as treatment decisions regarding local therapy have already been made, and the tumor characteristics already suggest a favorable prognosis with endocrine therapy alone 1.