image

By George Ochoa

The Oncotype DX Colon Cancer Assay (Genomic Health) alters treatment recommendations and may reduce medical costs and improve patient well-being, according to posters presented at the 2013 American Society for Clinical Oncology Gastrointestinal Cancers Symposium, held in San Francisco.

“This test is a useful tool for medical oncologists for risk assessment for their stage II patients beyond [how] the clinicopathologic factors alone can help us,” said Saima Sharif, MD, MS, assistant director of medical affairs for the National Surgical Adjuvant Breast and Bowel Project, and assistant professor of medicine at Temple University School of Medicine in Philadelphia. Dr. Sharif was not involved in the studies presented at the meeting.

One of the studies (abstract 453) involved 141 stage II, T3 mismatch repair (MMR)–proficient colon cancer patients from 17 centers in the Mayo Clinic Cancer Research Consortium. In this prospective study, researchers analyzed treatment decisions for these patients and found that the use of the Oncotype DX Colon Cancer Assay changed treatment decisions 45% of the time, with treatment intensity decreasing for 33% of patients and increasing for 11%. Recommendations for chemotherapy fell from 52% pre-assay to 30% post-assay.

In a second study (abstract 391), researchers used the same data to evaluate cost and quality of life. Given the decrease in actual adjuvant chemotherapy recommendations (a 22% decline, from 52% pre-assay to 30% post-assay), average total direct medical costs were calculated to decrease by $4,203. The net effect on average patient well-being was a gain of 0.083 quality-adjusted life-years.

In a third study (abstract 349), 30 community-based and 20 university-based oncologists were surveyed to assess the agreement among physicians regarding their recurrence risk assessments of patients with stage II colon cancer. Each physician made an assessment in 10 cases using only clinicopathologic factors, and in 10 separate cases using clinicopathologic factors plus the Oncotype DX Colon Cancer Assay recurrence score and MMR tests. Addition of the Oncotype DX Colon Cancer Assay significantly increased agreement among physicians in their recurrence risk assessments, in both university and community settings.

“I have used [the Oncotype DX Colon Cancer Assay] for selected cases, particularly those with pT3N0 pathologic stage or when there are conflicting traditional clinicopathologic features that, in some cases, are not supported by a consistently high level of evidence,” said Robin Katie Kelley, MD, assistant professor of medicine at the Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, and lead author of the study.

Dr. Kelley noted that the assay could be helpful “in cases with average-risk, stage II colon cancer, without distinct high- or low-risk features.”

“[The test] has been analytically validated for its accuracy, and … has clinical validity from two large randomized data sets,” she said.

Dr. Sharif said the Oncotype DX Colon Cancer Assay is a reliable assay based on retrospective data available for clinical use; however, it is yet to be evaluated prospectively in a randomized clinical trial to make treatment decisions and to look at outcomes of disease recurrence and death in patients.

“It is a useful tool for risk assessment of patients with stage II colon cancer but does not predict benefit from chemotherapy. … Based on each patient’s risk for recurrence, chemotherapy can be offered with the ‘hope,’ but no definitive evidence, that it will improve outcome of disease recurrence or death from cancer,” she said.

According to Genomic Health, the Journal of Clinical Oncology has accepted results from the second large clinical validation study of the Oncotype DX Colon Cancer Assay for publication.

Dr. Kelley reported receiving research funding from Genomic Health for research on the clinical utility of the Oncotype DX Colon Cancer Assay. Dr. Sharif reported involvement with clinical trials from which samples of tumor tissue were used to develop the assay, but he was not directly involved with its development.