New Data Presented at ASCO Gastrointestinal Cancers Symposium Reinforce Clinical Benefits of Oncotype DX^® Colon Cancer Test

Two new studies presented at the recent American Society of Clinical Oncology’s Gastrointestinal Cancers Symposium provided further support for the use of the Oncotype DX colon cancer test as an independent predictor of recurrence risk in stage II colon cancer patients. The new results also suggest a potential role for the test in patients with stage III disease pending further study.

The first study, presented in a poster session at the conference, showed that the Oncotype DX colon cancer Recurrence Score^® result and number of nodes examined are independent predictors of recurrence in stage II colon cancer and both should be considered when assessing individual recurrence risk in this patient population. The second study, presented in an oral discussion, analyzed various biological similarities and differences between stage II and III colon cancer. Results suggest the Oncotype DX Recurrence Score result is stage independent, and that it may also predict recurrence risk in stage III colon cancer.

"Some tumor characteristics, such as grade, and a small number of individual genes were identified that may distinguish stage II and III colon cancers. However, there is a striking similarity between the two stages for the vast majority of the 375 genes studied and for the 12-gene Oncotype DX colon cancer Recurrence Score," said Michael J. O'Connell, M.D., associate chairman of the NSABP. "As physicians begin to incorporate Oncotype DX into clinical practice for stage II colon cancer patients, it is worth conducting additional studies to evaluate this test for treatment planning in stage III disease, based on the similarities observed in this study."

Both studies used Genomic Health's quantitative RT-PCR technology to analyze RNA expression from 30 micrometers of manually microdissected fixed paraffin-embedded primary colon cancer tissue.

• The first study (Abstract 331) utilized data from the landmark QUASAR trial to assess the prognostic value of nodal assessment in combination with other variables including the Oncotype DX Recurrence Score result. Number of nodes examined was available for 657 of 711 patients randomized to surgery alone, and was significantly associated with recurrence risk as a continuous variable, after controlling for age, T-stage, grade, lymphovascular invasion, mismatch repair and year of randomization. Both Recurrence Score and number of nodes examined were independent predictors of recurrence risk (p=0.01 and 0.05, respectively). Additionally, the study results proved consistent with the National Comprehensive Cancer Network's recommendation of 12 or more nodes examined as a target for nodal assessment.
• The second study (Abstract 280) compared pathologic markers and gene expression by stage in four studies conducted to develop the Oncotype DX colon cancer test. Pathologic markers and expression of 375 genes were compared between 634 stage II and 844 stage III patients. Results demonstrated that the vast majority of the 375 genes and the Recurrence Score showed no significant interaction with stage, and there were similar patterns of gene expression by stage. However, there were differences identified between stage II and stage III colon cancer for some tumor characteristics and a small number of the individual genes. Stage II patients were more likely to be mismatch repair deficient (p=0.04) and have mucinous histology (p=0.007). Additionally, interaction of grade and stage was significant (p=0.005), and interactions of stage with T-stage, mismatch repair and mucinous histology were borderline (p=0.07 - 0.11), indicating prognostic value in stage II, but not stage III disease.