Clinical Services

Colorectal BioStrat® Assay

Colorectal Cancer - Background

Colorectal cancer (CRC) is the third most common cancer and the third leading cause of cancer death in men and women in the United States.In 2014, it is estimated that there will be 136,830 new cases of colon and rectum cancer and an estimated 50,310 people will die of this disease.1 Most colorectal cancers arise from adenomatous polyps (adenomas), in a process described as the adenoma-carcinoma sequence.2 Like other cancers, initiation and progression of CRC are associated with an accumulation of alterations in the function of key regulatory genes and genetic instability.

The appropriate management of individuals with precursor polyps is of utmost importance; since some of these individuals will develop adenomas again, even after endoscopic removal, and a small percentage will go on to have colorectal cancer. Using current histological techniques, differentiating between adenoma and carcinoma can be challenging in certain cases, and identifying those adenomas with a high risk for progression to cancer is not possible. An appropriately selected panel of genetic markers associated with adenoma recurrence or progression to carcinoma holds the promise of paving the way for individualized management of colorectal cancer patients based on the cytogenetic elements in tumor development.

The recent introduction of molecular cytogenetic techniques, especially the application of FISH probes in interphase cells of histological sections, may serve as a genetic diagnostic enhancement to assess the malignant potential of excised colorectal lesions, by detecting chromosomal alterations that are linked to the initiation and progression of colorectal cancer.

Introduction to Colorectal BioStrat® Assay

The Colorectal BioStrat® Assay is designed to detect copy number of chromosomes 7, 15, 18 and 20 via fluorescence in situ hybridization (FISH) in formalin-fixed, paraffin-embedded colorectal polyp/tissue specimens.

When hybridized and visualized, these probes provide quantitative information on chromosome copy number alterations relating to the detection of active and/or potential colorectal neoplasia and the differentiation of adenoma from adenocarcinoma. With the assay result and taking into account other standard diagnostic procedures, the physician and patient can make more informed decisions regarding the surveillance and management of colorectal polyps.

Criteria for Colorectal BioStrat® Abnormality

A specimen is considered 'positive' for FISH-associated evidence of colorectal dysplasia or adenocarcinoma if at least one of the following criteria is met:

  1. ≥10% cells are detected with a gain of chromosomes 7 and/or 15 and/or 18 and/or 20; or
  2. ≥35% cells have any deletion of chromosomes 7 and/or 15 and/or 18 and/or 20.

In addition, FISH results can be classified into 'low-risk' and 'high-risk' groups for prognostic analysis.

  1. Low-risk FISH
    1. Negative-FISH result; or
    2. Positive-FISH result
      1. < 25% cells showing gains for one or more chromosomes 7, 15, 18 and 20; or
      2. Losses for one or more chromosomes 7, 15, 18 and 20
  2. High-risk FISH
    1. Positive-FISH result
      1. ≥25% cells showing gains for one or more chromosomes 7, 15, 18 and 20

Analysis of ongoing data shows that patients with multiple chromosome gains detected in a colorectal specimen progress to adenoma/adenocarcinoma significantly earlier than patients with other FISH abnormalities. The finding of chromosome loss or gain of a single chromosome appears to be associated with a risk for progression that is less than patients with a result showing multiple chromosome gains but significantly greater than those with a negative FISH result.

Colorectal BioStrat® Images

The following examples of patient specimens demonstrate both the clinical utility of the Colorectal BioStrat® Assay as well as its simplicity of interpretation.

Colorectal Figure 1 Figure 1: Normal result observed in a colorectal cell after hybridization with the chromosomes 7, 15, 18 and 20 FISH probe showing two chromosome 7 (green), two chromosome 15 (aqua), two chromosome 18 (red) and two chromosome 20 (gold) signals.
Colorectal Figure 2 Figure 2: Abnormal result observed in a colorectal cell after hybridization with the chromosomes 7, 15, 18 and 20 FISH probe showing three chromosome 7 (green), seven chromosome 15 (aqua), eight chromosome 18 (red) and seven chromosome 20 (gold) signals.

The Colorectal BioStrat® Advantage

Colorectal BioStrat® Assay may be used not only in the differential diagnosis of colonic adenoma from adenocarcinoma but also to help identify adenomas with high risk for progression to carcinoma. This distinction is critical from a patient care perspective and may permit more effective targeting of repeated colonoscopy for patients at particularly high risk of progression thus providing a greater potential for prevention through polypectomy.

Combined with other standard surveillance methods, the Colorectal BioStrat® Assay provides valuable information regarding the molecular events surrounding the development of dysplastic change and progression to adenocarcinoma further assisting physicians and patients make more informed decisions regarding the surveillance and management of patients with colorectal polyps.

Ordering

Please contact BioVantra Client Support Center at (866) 301-0960 to arrange for Colorectal BioStrat® Assay testing. Our experienced Client Support Team can assist with:

  • Colorectal BioStrat® Assay Requisition
  • Sample requirements
  • Logistics and specimen transportation
  • Testing methodology
  • Report delivery, status or interpretation
  • Expert oncology and pathology consultations
  • Requests for BioVantra literature and scientific references

References

  1. Siegel R, DeSantis C and Jemal A: Colorectal Cancer Statistics, 2014. CA Cancer J Clin. 64: 104-117, 2014.
  2. Fearon E. and Vogelstein B: A genetic model for colorectal tumorigenesis. Cell. 61(5): 759-67, 1990.