The Oncotype DX test is a genomic assay that examines the activity of specific genes within a breast cancer tumor sample. This test helps personalize breast cancer treatment by providing information about the tumor’s biology and predicting its likely behavior. It analyzes tissue from surgery or biopsy to understand how genes influence cancer growth and spread, assisting healthcare providers in making informed decisions about therapies after surgery.
The test offers a precise understanding beyond standard pathology reports. It helps identify the potential for cancer recurrence and whether chemotherapy would offer a meaningful benefit, aiming to optimize treatment outcomes and potentially avoid unnecessary treatments and their associated side effects.
Who is a Candidate for the Oncotype DX Test?
The Oncotype DX test is not suitable for all breast cancer diagnoses; specific criteria determine eligibility. It is primarily recommended for individuals with early-stage invasive breast cancer. This means the cancer has grown beyond the milk ducts or lobules and has the potential to spread.
The cancer must also be estrogen receptor-positive (ER-positive), indicating that the cancer cells grow in response to the hormone estrogen. Furthermore, the cancer needs to be human epidermal growth factor receptor 2-negative (HER2-negative), meaning it does not have high levels of the HER2 protein, which would otherwise suggest different treatment pathways.
Patient lymph node status is also a determining factor. The test is commonly used for those with node-negative breast cancer, where cancer cells have not spread to the lymph nodes. It may also be considered for individuals with a limited number of positive lymph nodes, typically one to three.
Understanding the Recurrence Score
The Oncotype DX test provides a numerical Recurrence Score, ranging from 0 to 100. This score is derived from analyzing the expression levels of 21 specific genes within the tumor tissue. It serves as a prognostic indicator, estimating the likelihood of breast cancer returning in a distant part of the body.
A lower score suggests a reduced chance of distant recurrence, while a higher score indicates an increased risk. For example, a score of 0-17 typically signifies a low risk of recurrence, with the chance of cancer returning within nine years with hormone therapy alone often in the single digits. An intermediate score, generally between 18 and 30, suggests a moderate risk. Scores of 31 or higher are associated with a higher risk of distant recurrence.
These recurrence percentages assume the patient receives hormone therapy as their only systemic treatment after surgery. The score helps patients and their doctors understand the tumor’s biological aggressiveness and assess the long-term outlook.
Assessing the Benefit of Chemotherapy
Beyond predicting recurrence risk, the Oncotype DX test also indicates how much a patient might benefit from adding chemotherapy to their treatment plan. This distinct function guides decisions about the intensity of adjuvant therapy after surgery, helping determine if chemotherapy will significantly reduce the risk of cancer recurrence or death.
Patients with a low Recurrence Score, typically 0-25 for postmenopausal women with or without lymph node involvement, generally show minimal to no benefit from chemotherapy. In these cases, the risks and side effects often outweigh any potential advantage. For premenopausal women with node-negative cancer, a score of 0-15 also indicates chemotherapy is unlikely to add much benefit.
For those with higher Recurrence Scores, such as 26-100, the test indicates a greater potential benefit from chemotherapy. For premenopausal women aged 50 or younger with node-negative cancer, a score between 16 and 20 may suggest a small benefit, while scores of 21-25 indicate a greater likelihood of benefit.
Evidence Supporting Test Accuracy
The accuracy of the Oncotype DX test is supported by findings from extensive clinical trials. The TAILORx trial, a large study involving over 10,000 women with hormone receptor-positive, HER2-negative, node-negative breast cancer, played a significant role in validating the test. This trial aimed to determine the role of chemotherapy for women with intermediate Recurrence Scores.
The TAILORx results, published in 2018, showed that most women with intermediate scores (11-25) did not benefit from adding chemotherapy to hormone therapy. Their outcomes, including distant recurrence-free survival and overall survival, were similar whether they received hormone therapy alone or with chemotherapy. This finding confirmed that many women could safely forgo chemotherapy, avoiding its side effects without compromising their survival.
Earlier studies, such as NSABP B-14 and NSABP B-20, also contributed to the test’s validation. NSABP B-14 demonstrated the Recurrence Score’s ability to predict distant recurrence in node-negative, ER-positive patients treated with tamoxifen. NSABP B-20 further showed that the test could predict the benefit of chemotherapy in similar patient populations, identifying a subset who would gain significant advantage from its addition.