At the recent American Society of Clinical Oncology Gastrointestinal Cancers Symposium (ASCO GI), Genomic Health presented the results of two studies from its colon cancer development program.  These studies have identified genes that could help predict the likelihood of disease recurrence as well as potential chemotherapy benefit for early-stage (stage II and III) patients with colon cancer.

Both study reports used RT-PCR technology to analyze RNA expression from 375 cancer-related and reference genes from the colon tumors of patients who were treated with surgery alone or with surgery plus adjuvant 5-fluorouracil/leucovorin (5-FU/LV) chemotherapy.

The first report evaluated colon cancers from patients treated with surgery alone, including 270 patients from the National Surgical Adjuvant Breast & Bowel Project (NSABP) C-01/C-02 study and 765 patients who were treated at the Cleveland Clinic. Researchers identified 65 genes significantly associated with colon cancer recurrence across both patient populations. The range of individual gene expression was associated with an up to 11-fold difference in risk of disease recurrence.

The second report analyzed colon cancers from an additional 508 patients who were treated with surgery plus 5-FU/LV chemotherapy in NSABP study C-06. Of the 375 genes, the researchers identified 56 that were significantly associated with disease prognosis for stage II and III colon cancer in this study as well as in patients treated with surgery alone in NSABP C-01/C-02 and at the Cleveland Clinic. Furthermore, the study collaborators used 15 of the 56 genes in a preliminary model to stratify patients into recurrence risk categories.

Genomic Health has completed four independent studies involving 1,851 colon cancer patients to evaluate a total of 761 genes. These data will support the selection of the final gene set, which is the next step in developing a colon cancer test that is intended to quantify both the risk of recurrence and likelihood of chemotherapy benefit from giving patients 5-FU/LV in the adjuvant setting.  This final gene set will then be evaluated in an independent validation study, which we expect to get underway later in 2008.