1p/19q Co-deletion

1p/19q Co-deletion Test at Jaipur Molecular Lab

The 1p/19q co-deletion test is a genetic test used primarily in the diagnosis of oligodendrogliomas, a type of brain tumor. This genetic test looks for the loss of genetic material on chromosomes 1 and 19, which is commonly found in this type of tumor. The presence of a 1p/19q co-deletion is crucial in guiding the prognosis and treatment decisions for patients with oligodendrogliomas and related conditions. Here’s a detailed look at the test:

1. What is 1p/19q Co-deletion?

• Definition: The 1p/19q co-deletion refers to the simultaneous loss of genetic material from chromosome 1 (p-arm) and chromosome 19 (q-arm). This genetic alteration is found in a subset of oligodendrogliomas, a type of glioma that originates in the brain’s glial cells.
• Significance: The co-deletion is strongly associated with a better prognosis and a more favorable response to chemotherapy and radiation therapy in patients with oligodendrogliomas.

2. Clinical Significance

Diagnosis: The presence of the 1p/19q co-deletion differentiates oligodendrogliomas from other types of brain tumors, such as astrocytomas, which typically do not show this genetic alteration.

Prognosis: Tumors with this genetic alteration tend to grow more slowly, leading to a better overall prognosis and longer survival rates.

Treatment Response: 1p/19q co-deletion predicts a better response to chemotherapy and radiotherapy. Tumors with this alteration respond well to treatments, including drugs like PCV chemotherapy (procarbazine, lomustine, and vincristine).

Subtype Identification: The co-deletion identifies the oligodendroglioma subtype of gliomas, which is crucial for treatment and management decisions.

3. Testing Methods of The 1p/19q co-deletion at Jaipur Molecular Lab

The 1p/19q co-deletion at Jaipur Molecular Lab is detected using several molecular diagnostic techniques:

Fluorescence in situ Hybridization (FISH):

• Procedure: Fluorescent probes bind to specific regions of chromosomes 1 and 19. A loss of signals on these chromosomes indicates a co-deletion.
• Accuracy: FISH provides high specificity and is widely used to confirm 1p/19q co-deletion.

Polymerase Chain Reaction (PCR):

• Procedure: PCR amplifies specific DNA sequences from chromosomes 1 and 19, followed by comparison to a normal reference to detect deletions.

Next-Generation Sequencing (NGS):

• Procedure: NGS sequences the entire genome or specific regions of interest to identify deletions in chromosomes 1 and 19. Its use is increasing in research settings, providing more detailed information about other genetic alterations in gliomas.

Array Comparative Genomic Hybridization (aCGH):

• Procedure: This method compares the tumor’s genetic material to normal reference DNA, highlighting any missing or extra genetic material (e.g., 1p/19q deletions).

Single Nucleotide Polymorphism (SNP) Array:

• Procedure: SNP arrays detect chromosome abnormalities, including deletions in 1p and 19q.

4. Test Interpretation

• Positive Test: A positive result confirms the deletion of both chromosome 1 (p-arm) and chromosome 19 (q-arm) in the tumor cells, indicating the presence of 1p/19q co-deletion. This result suggests a better prognosis and a favorable response to chemotherapy and radiation therapy.
• Negative Test: The absence of a 1p/19q deletion suggests that the tumor may belong to a different subtype (e.g., astrocytomas) and may not respond as well to therapies for oligodendrogliomas.
• Partial Deletion: Partial deletion of 1p or 19q may impact treatment decisions, requiring further genetic tests to understand the full scope of genetic alterations in the tumor.

5. Who Should Be Tested?

• Patients with suspected oligodendroglioma: The test determines whether the tumor is an oligodendroglioma, especially when histological features alone are insufficient.
• Tumor recurrence: Testing provides valuable insights into the tumor’s genetic changes over time.
• Glioma patients: Any patient undergoing treatment planning or clinical trial enrollment benefits from this test.

6. Impact on Treatment

• Chemotherapy: Patients with 1p/19q co-deletion experience better outcomes with chemotherapy. PCV chemotherapy is often preferred for these patients.
• Radiation Therapy: These tumors also respond better to radiation therapy.
• Targeted Therapies: While no specific targeted therapy for 1p/19q co-deletion exists, this genetic information informs treatment strategies and clinical trial eligibility.

7. Prognosis and Survival

• Favorable Outcome: Oligodendrogliomas with 1p/19q co-deletion exhibit better prognosis, with longer overall survival (OS) and progression-free survival (PFS) compared to tumors without the co-deletion.
• Survival Rates: Patients with 1p/19q co-deletion may live significantly longer (up to 10 years or more), while those without the deletion face poorer survival rates and more aggressive tumor behavior.

8. Conclusion

The 1p/19q co-deletion test plays a pivotal role in diagnosing and managing gliomas, particularly oligodendrogliomas. This test confirms the tumor’s genetic profile, informs treatment decisions, and predicts response to chemotherapy and radiation. It also provides prognostic insight, enabling clinicians to design personalized treatment plans for better outcomes.

References and Sources

• Molecular Diagnostics for Gliomas: “1p/19q Co-deletion Testing,” American Association of Neuropathologists, 2020.
• Journal of Clinical Oncology: “The Prognostic and Therapeutic Implications of 1p/19q Co-deletion in Gliomas,” 2019.
• European Society for Medical Oncology (ESMO): Guidelines on Genetic Testing in Gliomas, 2020.