RATIONALE: Determination of genetic markers for colorectal cancer may improve the identification of patients who are at highest risk for relapse.

PURPOSE: This clinical trial is studying the importance of genetic markers for detecting relapse in patients with colorectal cancer.

OBJECTIVES:

• Determine the clinical and pathologic significance of unstable DNA elements in colorectal cancer (tumor microsatellite instability).
• Determine the clinical and pathologic significance of loss of heterozygosity for chromosomes 5, 8, 17, and 18 (as the primary targets) and of chromosomes 1, 14, and 22 (as the secondary targets) in colorectal cancer.

OUTLINE: DNA is examined for unstable elements (microsatellite instability and loss of heterozygosity) by analyzing at least 10 separate (CA)n-repeats localized to 5 separate chromosomes (5q, 8p, 15, 17p, and 18q). Loss of heterozygosity is analyzed for at least four chromosomal arms (5q, 8p, 17p, and 18q) and later other chromosomes (e.g., 1, 14, and 22). Immunohistochemistry is used to test for the presence or absence of the genes involved in DNA mismatch repair (hMLH1 and hMSH2).

Patients do not receive the results of the genetic testing and the results do not influence the type or duration of treatment.

PROJECTED ACCRUAL: This study will accrue up to 708 specimens.

DISEASE CHARACTERISTICS:

• Must have had a resectable adenocarcinoma of the colon or rectum and must have participated in one of the following NCCTG randomized clinical trials:

  • 784852: No Treatment Control Versus Levamisole Versus Levamisole Plus Fluorouracil (5-FU)
  • 794604: No Treatment Control Versus 5-FU by Portal Vein Infusion
  • 794751: Postoperative Radiation Versus Postoperative Radiation Plus Sequential Chemotherapy with Methyl CCNU and 5-FU
  • 844652: An Intergroup Study - An Evaluation of Levamisole Plus 5-FU as Surgical Adjuvant Treatment for Resectable Adenocarcinoma of the Colon
  • 864751: Phase III Protocol for Surgical Adjuvant Therapy of Rectal Carcinoma: A Controller Evaluation of (A) Protracted-Infusion 5-FU as a Radiation Enhancer and (B) 5-FU Plus Methyl-CCNU Chemotherapy
  • 874651: M/N - A Controller Evaluation of Recombinant Interferon-gamma (IFL GM) and 5-FU and Folinic Acid With or Without Levamisole as Adjuvant Treatment for Resectable Adenocarcinoma of the Colon
  • 894651: A Controller Phase III Evaluation of 5-FU Combined With Levamisole and Leucovorin as Adjuvant Treatment for Resectable Colon Cancer

• Tissue blocks from the primary colorectal cancer must have been received by the NCCTG operations office

Patients have resectable adenocarcinoma of the colon or rectum and has been previously enrolled on N784852, N794604, N844652, N864751, N874651, and N894651.