Understanding Cancer Genomic Profiling

What is Cancer Genomic Profiling?

Cancer genomic profiling tests look for genetic mutations in the tumor of cancer patients. This helps physicians to identify suitable treatments based on the features of the cancer cells at a molecular level. This approach is sometimes called tumor profiling, precision medicine, or personalized medicine.

Cancer genomic profiling can provide information to help answer questions such as "Which targeted therapies are likely to work for me?" or "Would Immunotherapy be effective for me?" Our tests can also help predict prognosis, evaluate whether chemotherapy is necessary, monitor cancer recurrence, and much more.

Different Therapies for Different Tumors

Which targeted therapies are suitable for me?

Targeted therapy works by focusing on specific targets that are found in cancer cells, thus is an effective way to selectively affect cancer cells while sparing most normal cells. Different targeted therapies aim at different drug targets, and different patients may have different targets in their tumors. Therefore, testing to confirm whether your tumor possesses drug targets will help your physician determine which targeted therapy would be most effective for you.

Would immunotherapy be right for me?

Immunotherapy has shown impressive outcomes for some patients, but it is certainly no miracle cure just yet. The biggest problem faced with immunotherapy is its low response rate, with only approximately 20% of patients responding to treatment on average. Genomic tests are available to help predict whether a patient might benefit from immunotherapy.

When a tumor harbors many genetic mutations, the cancer cells will look vastly different from normal cells. This allows our immune system to recognize and attack the cancer cells more easily. Therefore, tumors with high numbers of genetic mutations tend to have a better response to immunotherapy. Comprehensive genomic profiling can evaluate immunotherapy by calculating the total number of genetic mutations (known as the Tumor Mutational Burden, TMB) carried by the cancer cells.

*There are many types of immunotherapy. The type of immunotherapy discussed here is immune checkpoint therapy.

Different Types of Tests

Of the 20,000 genes in human cells, approximately 400 genes are strongly associated with the formation of cancer. As a result, most tumor profiling tests used in clinical settings usually focus on these 400 cancer-related genes or those that are more frequently mutated among these 400 genes.

Single Gene Tests

Screen one gene at a time. Single-gene tests are affordable but provide limited information for physicians. A common example of a single-gene test is the EGFR test for non-small cell lung cancer.

Multi-gene Tests

Screen many genes at a time. Some tests cover the dozens of genes that are most frequently mutated and have corresponding targeted therapy. There are also Comprehensive Genomic Profiling tests that screen the 300-400 cancer-related genes, providing more comprehensive information for physicians to find a suitable targeted therapy and evaluate immunotherapy as a viable treatment option.

In addition to the number of genes, physicians also look at which genes are tested (different genes are more frequently mutated in different cancer types), whether the test covers "hotspots" only or entire genes, and so on. It is important to discuss with your physicians first to see what might be suitable for you.

When to Consider Multi-gene Tests

Although single-gene tests may cost less, sometimes physicians will suggest testing for hundreds of genes simultaneously using comprehensive genomic profiling, especially for the following conditions:

• Current Treatment is Not Effective

Doctors are more likely to suggest testing for many genes if the patient's current treatment is ineffective, or if the patient develops drug resistance, or experiences multiple relapses. This will help doctors understand why the previous treatments were not effective and identify new treatment options.

• To Consider Immunotherapy

Physicians may suggest comprehensive genomic profiling to evaluate if the patient is likely to benefit from immunotherapy (immune checkpoint therapy). To evaluate immunotherapy, the test needs to cover at least 300-400 cancer-related genes to be able to calculate what is called the tumor mutational burden (TMB), that is, the total number of genetic mutations carried by the cancer cells.

• To Save Time / Only Have a Limited Tissue Sample

As new targeted therapies continue to be developed, more drug targets must be tested. Because each test takes at least two days and requires a portion of the tissue sample (obtained during biopsy or surgery), using single-gene tests to look for drug targets one at a time will be time-consuming, and the tissue sample may run out. Physicians may suggest testing many genes simultaneously to save time and when the amount of the patient’s tissue sample is limited.

Overall, testing hundreds of genes increases the likelihood of detecting genetic mutations and provides more comprehensive information for doctors to identify a suitable treatment. However, sometimes mutations may be detected, but a matching targeted therapy (A) has not been developed yet, (B) may still be under clinical trial, or (C) may be approved for another cancer type. Under scenarios (B) and (C), not as much information is available about the treatment effects and side effects of the drug, so it is important to discuss with your physician to weigh up the risks and benefits.

Consult Your Doctor First

Cancer management is highly complex. Different genomic tests are available for different types of cancer. In addition to genomic profiles, the physician must consider many factors, including the patient's physical condition and treatment history. Therefore, it is essential to seek advice from your doctor and have them comprehensively evaluate whether genomic testing might suit you.

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