Chromosome 18q Allelic Loss, Frozen Tissue
| Chromosome 18q Allelic Loss, Frozen Tissue | | | |
| Number | | 480459 |
| CPT | | 83891 (x2); 83900 (x2); 83901 (x8); 83909 (x2); 83912 |
| Related Information | | Microsatellite Instability |
| Synonyms | | 18q Allelic Loss for Colorectal Cancer Prognosis ; 18q Loss of Heterozygosity |
| Special Instructions | | Please direct any questions regarding this test to Oncology Customer Service at 800-533-0567. |
| Specimen | | One tumor specimen (fresh or frozen) and normal tissue (either fresh or frozen) or whole blood |
| Volume | | One tumor specimen (fresh or frozen) and normal tissue (either fresh or frozen) or 7 mL whole blood |
| Minimum Volume | | One tumor specimen (fresh or frozen) and normal tissue (either fresh or frozen) or 3 mL whole blood |
| Container | | Solid tumor and normal colonic mucosa in a 60 mL solid tumor biopsy bottle (fluorescent pink) and whole blood in lavender-top (EDTA) tube or yellow-top (ACD-A) tube |
| Collection | | Submit fresh tissue and blood at room temperature and frozen tissue on dry ice. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested. |
| Storage Instructions | | Fresh tissue in a solid tumor biopsy bottle in media should be stored at 4°C. Frozen tissue should be stored at -20°C. Maintain whole blood at room temperature. |
| Causes for Rejection | | Normal or tumor tissue missing; hemolyzed blood; insufficient quantity for analysis |
| Use | | Identify tumors with chromosome 18q allelic loss (loss of heterozygosity) which is a prognostic marker in colorectal cancer. The prognosis in patients with stage II cancer and chromosome 18q allelic loss is reported to be similar to that in patients with stage III cancer, who are thought to benefit from adjuvant therapy. This assay can also detect microsatellite instability (MSI). MSI is observed in >85% of cases of hereditary nonpolyposis colorectal cancer (HNPCC) and also in approximately 15% of sporadic colorectal cancers. Tumors exhibiting MSI are reported to have a lower tendency to metastasize and these have a better survival compared to patients with microsatellite stable tumors. |
| Limitations | | The provided tumor tissue should be composed of ≥40% tumor cells for accurate test interpretation. Allelic loss of chromosome 18q and microsatellite instability in colon tumors are prognostic markers. The role of these as predictive markers of response to adjuvant therapy has yet to be defined. The markers utilized in the 18q allelic loss assay, while able to detect microsatellite instability, are not the recommended panel of markers designed for the detection of MSI. Microsatellite instability can be assessed using the NCI recommended panel of markers (see Microsatellite Instability [511311] ). |
| Methodology | | Multiplex polymerase chain reaction (PCR); capillary electrophoresis |
| References | | Baddi L and Benson A 3rd, “Adjuvant Therapy in Stage II Colon Cancer: Current Approaches,” The Oncologist, 2005, 10:325-31. Jen J, Kim H, and Piantadosi S, “Allelic Loss of Chromosome 18q and Prognosis in Colorectal Cancer,” N Engl J Med, 1994, 331(4):213-21. Ogunbiyi OA, Goodfellow PJ, Herfarth K, et al, “Confirmation That Chromosome 18q and Prognosis in Colorectal Cancer Is a Prognostic Indicator,” J Clin Oncol, 1998, 16(2):427-33. |
|