Intratumoral molecular or genetic markers as predictors of clinical outcome with chemotherapy in colorectal cancer

Identification of molecular markers at either the intragenic, chromosomal, mRNA, or protein level that might predict whether colorectal cancer patients are likely to benefit from adjuvant or palliative therapy is a high priority. The majority of clinical studies addressing this issue, particularly those done in the adjuvant setting, analyzed tumor samples from patients treated in the era when 5-fluorouracil (5-FU) alone or combined with leucovorin or levamisole were the mainstay of therapy. This review highlights some of the intratumoral molecular markers that may have importance as predictors of benefit with 5-FU-based therapy. Although the goal of these investigations is to one day permit selection of therapy for an individual patient based on the tumor phenotype, prospective studies have yet to be conducted that test whether selection of therapy based on molecular markers results in an improved outcome.