When genomic testing indicates that chemotherapy is unnecessary and women choose to forgo it, a recent prospective study found that nearly all remained disease-free 5 years later. Among patients whose breast cancer was classified as low-risk, 85% chose to forgo chemotherapy, and 97% were disease-free 5 years later.1 These powerful results suggest the growing importance of genomic testing in everyday clinical practice.

Information on prognosis, whether the patient would benefit from chemotherapy or hormone therapy, and support for decisions regarding potential treatment are derived from genomic testing. “Indirectly, genomic testing gives us an idea of what the risk of the cancer recurring is,” said Alison Laidley, MD, FACS, of Texas Breast Specialists in Dallas, Texas.

Genomic testing uses a sample from a patient’s tumor to query a set of genes. The genomic tests available for use in the clinic for breast cancer include MammaPrint, a lead test in the Symphony suite of breast cancer tests (Agendia; Irvine, California); OncotypeDX (Genomic Health Inc; Redwood City, California); and Target Now (Caris Life Sciences; Irving, Texas). Information from these tests can inform decisions on the patient’s prognosis and predict which therapies may be needed. Although guidelines suggest that a majority of women with node-negative, estrogen receptor-positive (ER+) breast cancer should be offered chemotherapy, only a minority of patients will experience recurrent disease so its benefits for some patients may be very little.2,3

“The last thing a woman wants to do is chemotherapy,” explained Laidley. Many women would rather have their breast removed than undergo chemotherapy. If information from a test can help some women avoid chemotherapy, then that’s a bonus. However, if the test indicates that chemotherapy is very necessary, we can offer them extra information and support for their choice, Laidley added.

The recently reported RASTER trial provides prospective evidence to support the use of genomic testing in making decisions about chemotherapy.1 The TAILORx and RxPONDER trials are addressing the question of whether adding adjuvant chemotherapy to endocrine therapy provides additional benefit for patients who are assessed as intermediate-risk by gene-based assays.4

HOW MEDICAL ONCOLOGISTS USE GENOMIC TESTS

Early-stage breast cancer patients who fall into a gray zone regarding if chemotherapy would be beneficial are the most likely ones to have the tests done, explained Lillie D. Shockney, RN, BS, MAS, associate professor at the Johns Hopkins Schools of Medicine and Nursing. The proportion of patients who sent tissue samples for testing varies. Some clinics test samples from all patients, some from about half, and some from about a quarter.

Shockney explained that testing procedures vary. Sometimes the oncologist orders the test for any patient who meets the criteria for the test. In other cases, the surgeon may order the test so the results are ready when the patient meets with her oncologist. This approach is supported by a study in which difficulty in coordinating diagnostics relative to treatment decisions was identified as the most frequent concern by clinicians in regard to using gene expression profile testing.5 Ordering a test, obtaining insurance authorization, sending the specimen to an outside laboratory, receiving the results, and discussing the results with patients can be a lengthy and complex process. If the tests are not ordered with enough lead time, the results may not be available for making relevant decisions such as the use of adjuvant chemotherapy.

Shockney also stated that some clinicians only test stage I tumors with favorable prognostic factors that are truly in a gray area for benefit from chemotherapy. Yet other cancer centers will wait for the patient to inquire.

“I personally feel it is important for the oncologist to ask the patient early on about her feelings about [chemotherapy]. It is also really important for patients to understand that the risk of recurrence scores are based on the assumption that the patient will be diligent in taking her hormonal therapy as prescribed,” stated Shockney.

Choosing which test to use is up to the physician, explained Amy Fuller, RN, BSN, of Bon Secours St. Francis Health System in Greenville, South Carolina. Regarding guidelines and FDA approval, she said, “There are several genomic testing options available. However, OncotypeDX is the only test listed in the NCCN guidelines, and MammaPrint is the only test with FDA approval. They are probably the two most commonly used options.”

SIGNIFICANCE OF RESULTS ARE A WORK IN PROGRESS

Do clinicians act on the results of the test? “It’s a learning curve,” Laidley explained. Clinicians act on test results more frequently now than when the test first came out, as they’ve gained more understanding of the rationale and the data behind the test. “More clinical results have come out that look at and again solidify the validity of the tests. It’s not the only factor that is taken into consideration in terms of deciding about treatment for a patient,” said Laidley.

Laidley explained that medical oncologists consider the clinical and pathological features of the tumor, and then factor in the test results. The challenging part is when clinical and pathologic features suggest one thing, and the genomic test results indicate a treatment course that is either more or less aggressive. Then all of the evidence should be weighed to come up with a recommendation. When a situation does have discord, more and more weight is being put into the results of the genomic test.

“We now know that the biological behavior of the tumor dictates its behavior and no matter how good I am as a surgeon, I cannot beat biology with my scalpel. I need to listen to the technology that can tell me how the tumor behaves, and tailor my care accordingly,” said Beth Dupree, MD, FACS, medical director of the Breast Health Program at Holy Redeemer Health System in Philadelphia, Pennsylvania.