Advances in genomic profiling are helping doctors understand cancer patients’ gene mutations which will lead to better treatment choices and outcome.
FOUR decades ago, cancer was a mystery. There were a lot of unknown details about cancer cells and their mutations which affected how patients respond to treatment. That was the time when the approach to treatment was “one-size-fits-all”, regardless of the types and stages of cancer.
In recent years, however, there has been tremendous progress in everything cancer-related — from prevention and diagnosis to treatment.
While it may take many more decades before a cure for cancer is found, the current perception of the disease has changed.
It is no longer an immediate death sentence, but a treatable and manageable disease — depending on the type and staging, of course.
One of the progressive changes is advances in genomic profiling, used to detect distinct DNA (deoxyribonucleic acid) mutations of a patient’s tumour.
With the understanding of the patient unique gene mutation, oncologists are now able to match the disease to a targeted treatment.
In addition, genomic profiling is effective in helping patients with hard-to-treat cancers such as lung, rare cancers and those with unknown primary location.
Consultant Clinical Oncologist Dr John Low says cancer is a genetic disease which means there are damages to the DNA cells that cause the tumour growth.
Genomic profiling allows critical insights into each patient’s gene alterations or mutations. It can detect more than 300 genes in one test compared to the single gene marker.
He says it has always been difficult to obtain more biopsy tissues for the cancer gene that is located in hard-to-access areas. Unfortunately, with a single gene marker, there is a possibility of using up all the tissues, making it impossible to do another test to look for more mutations.
“But with comprehensive genomic profiling, we are looking for the whole section of the genes that may be responsible for the mutations. This way, we can give a more precise and effective treatment. It has also changed the way we treat cancer.
“Previously, we treat cancer of different origins in different ways. Now the test helps us to understand these cancers may share similar mutations. So the treatment plan has changed into treating all the mutations, rather than the location of the cancer in the body.”
BETTER CHOICES AND OUTCOME
Consultant clinical oncologist Dr Tho Lye Mun says genomic profiling has changed the landscape of cancer diagnosis and treatment.
Where patients may only have had limited treatment options previously, they now potentially have better choices and outcome.
Cancer cells form due to the acquisition of harmful genetic mutations. These mutation could be the result of multiple factors including environment and lifestyle. In a minority of cancers, it is due to a mutated gene that is inherited from one’s parents.
“Each cell in our body has specific code that defines its role and function. Each code is very lengthy, just like the words in a book. Even if one word is changed, the meaning of the whole book can be transformed.
“Similarly, when there is a mutation, the growth of the cell goes unchecked and become cancerous. For example, when you smoke, the chemicals inhaled can cause a change in the code of the cells in your lungs or throat which may lead to lung or throat cancer.
“If we know the code that is responsible for the mutation, we can then use the right medication to kill the cells bearing that mutation. But the problem is we don’t know which code is affected, unless we do genomic profiling.”
Dr Tho, who holds a doctorate in cancer cell and molecular biology, says there are a huge number of known genetic mutations, at least over 1,000, that can cause cancer.
Usually the number of mutations increases as the cancer progresses from stage one to four leading to the cancer becoming more and more aggressive.
It is not easy to distinguish a mutation that doesn’t have much overall consequence versus one that is primarily responsible for the tumour going out of control.
“We need to target the latter not the former. So interpretation of the results is just as, if not more important, than performing the test. It requires experience and knowledge to interpret a genetic test result,” says Dr Tho, who had performed more than 100 cases genomic profiling.
BETTER SURVIVAL RATE
Dr Tho says decades ago, there was a lot of trial and error with treatment. Doctors would try one treatment and if it didn’t work they would continue to find one that would. Genomic profiling has allowed doctors to select the right treatment from the start and this saves time.
The test is usually done for later stage cancers because conventional therapies such as surgery, radiotherapy and chemotherapy may have limited effect.
As time is crucial for these patients, there is greater need for novel or targeted therapies. In recent years, cancer survival rates have improved multiple folds, due to targeted therapies.
There may also be a need to do another profiling if the remaining tumour cells acquire a new mutation which can become resistant to the previous treatment. Only through another profiling can the identity of the new mutation detected.
This situation frequently happens in lung cancer bearing an epidermal growth factor receptor mutation (EGFR) such as exon 19 deletion. Patients benefit from first and second generation EGFR inhibitors but then may develop a new mutation (EGFR T790M). Once detected, patients can be switched over to third generation EGFR inhibitors successfully.
Some newer mutation are recognised such as MET amplification and mutation, RET, HER2, NTRK, all of which have drugs to target them. These new mutations are found only through genomic profiling and it has helped the outcome for lung cancer patients.
“In this day and age, stage four lung cancer patients may survive five years or more with targeted therapy. About 15 to 30 per cent can survive five years or more with immunotherapy. This is so different from 20 years ago. Back then, doctors did not even talk about a two- or three-year survival rate for such patients.”
Although genomic profiling has helped tremendously in the detection of cancer gene mutation, the barrier is lack of available drugs to target them.
“Unfortunately, science is lagging behind in terms of drug discovery. In cases where we don’t have the drugs, we have to use conventional therapy.
“That is why research is important and I am hopeful that in the next 20 to 30 years, there will be many more drugs to keep up with diagnostic technology. New drugs are constantly being introduced. The future looks bright for cancer therapy,” says Dr Tho.