[gdpawel]

Cary Presant, M.D.
Wilshire Oncology Medical Group

The decision of chemotherapy plus hormonal therapy versus hormonal therapy alone in patients with breast cancer, stage 1 or 2A is an important decision which we commonly make in our oncology practices. The advent of the Oncotype DX test, along with other similar tests such as MammaPrint and Mammostrat, have given us tools whose application is selectively very important. Recently, the adoption of gene expression profile testing has been reviewed by M. Hassett and coworkers (Journal of Clinical Oncology 30:2218-2226, 2012).

In over 7,000 women, 20% received gene expression profile testing. Of those who had the test, 50% received chemotherapy. The use of gene expression profiling became more common between 2006 and 2008 (increasing from 14.7% to 27.5%). Unfortunately, they did not have more up to date data in the past 4 years.

Needless to say, if an oncologist sees a clinical indication to use chemotherapy, addition of a gene expression profile test would be unnecessary. Similarly, if a patient were unwilling to consider chemotherapy, such a test would again be unnecessary. However, for women wanting the most appropriate, personalized, individualized therapy, the use of a gene expression profile test would be very important.

Surprisingly, in the Hassett analysis, small, node negative cancers were associated with a higher odds of chemotherapy use. Surprisingly, node positive and large node negative cancers were associated with a lower chance of chemotherapy use following testing.

Today, the use of this testing is extremely widespread in my community. At each tumor board, patients with stage 1 or 2 breast cancer are nearly universally recommended for such testing. The NCCN clinical practice guidelines suggests using this test to help make the clinical decision regarding the addition of chemotherapy.

However, the intermediate risk group identified in the Oncotype DX testing is still the subject of an ongoing randomized phase III clinical trial. So the application of the test may not be associated with a clear cut answer as to whether or not chemotherapy is useful. Indeed, the frequency of intermediate test results seems to be increasing (Abstracts ASCO 2012). It is important to realize that until such a trial to determine the predictive utility of an intermediate result is completed, the study may be inconclusive. Furthermore, none of the gene expression profile tests have been subjected to a phase III prospective randomized trial (so far only retrospective data has been used).

In my practice, discussing the uncertainty of this testing and applying one of the tests selectively is an important component of breast cancer adjuvant care. Therefore, such patients require several comprehensive visits to both evaluate the appropriateness of possible chemotherapy, and to evaluate the results of testing.

The advance that these tests provide in care of cancer patients must be associated with continued awareness of the results of ongoing randomized prospective trials. The application of similar tests to colorectal cancer, lung cancer and other tumors remains a challenge for clinical trials as well as for the adoption into clinical practice.