Thanks to new therapies developed over the last 15 years, patients with lung cancer are now able to live longer than before, said Dr Lim Hong Liang, a senior consultant in medical oncology at Parkway Cancer Centre (PCC).
“Relying on chemotherapy alone to treat cancer is not a very good option,” said Dr Lim, who was speaking at PCC’s inaugural annual cancer update seminar held last year at the Pan Pacific Singapore hotel in July last year.
In his talk, “Improving Lung Cancer Treatment with Targeted Therapy and Immunotherapy”, Dr Lim said that in the last 15 years, new treatments such as targeted therapy and now, immunotherapy, have improved cancer survival rates.
Patients who are treated with chemotherapy and targeted therapy have median survival rates of 21/2 to three years, compared to just 12 months from only undergoing chemotherapy treatment.
What is targeted therapy?
A treatment that targets the cancer cells, targeted therapy, is based on the type of mutation that the cancer cells might have.
Back in 2004 in the United States, the first mutation was discovered in the epidermal growth factor receptor (EGFR) gene. A drug called Iressa that was able to target cancer cells with this mutation was developed.
Since 2004, more mutations have been discovered and more drugs have been developed to target these mutations.
Chemotherapy affects all cells while targeted therapy is more focused. As a result, side effects from targeted agents are likely to be mild.
In addition, the response is often rapid and usually associated with a significant reduction in tumour volume.
This translates to a rapid improvement of tumour-related symptoms such as pain and a cough. The tumour can also often be under control for a longer time with targeted treatment.
“It is common to have a good response to targeted therapy,” said Dr Lim.
He mentioned a patient of his who did not want to undergo chemotherapy and was on Iressa alone. That patient survived 31 months. As most targeted agents are in oral form, it saves patients from frequent cannulations and visits to clinics for infusions.
Targeted therapy is also useful for patients whose cancer has metastasized, or spread, to the brain.
Unlike chemotherapy, targeted agents penetrate the body more effectively due to receptors – an “antenna” on the cell surface – to receive and interpret messages sent via the bloodstream from other organs. This results in higher drug levels in the brain, which could bring about better tumour control.
That said, targeted therapy is not an option for all cancer patients. For instance, not all lung cancer patients have a cancer whose mutation can be targeted.
Fortunately, there are now other options, including a new treatment known as immunotherapy.
Immunotherapy uses drugs to stimulate or make changes to the body’s immune system to help it identify and fight cancer cells.
“We have been researching on how the immune system can be used for this purpose for many years, but we have had no success until a few years ago,” said Dr Lim.
One of the ways tumour cells evade the detection and destruction by the immune system is through overexpression of the PD-L1 protein on their surfaces.
Lung cancer: High occurrence, low survival rates
In Singapore, lung cancer is the second most common cancer in men and the third most common cancer in women.
Men are three times more at risk of contracting lung cancer compared to women. Among the three major ethnic groups, the Chinese have the highest risk, followed by the Malays and Indians.
There are two main types are lung cancer: small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC).
More than 80 per cent of all lung cancers are NSCLC, which tends to grow and spread more slowly. If discovered early, it can be cured with surgery or radiotherapy. SCLC, on the other hand, grows and spreads rapidly.
However, lung cancer tends to be discovered late, which is why lung cancer survival rates are still relatively low for now.
Antibodies that target either PD-1 or PD-L1 can allow the body’s immune cells to recognise and kill the cancer cells.
Drugs such as Keytruda and Opdivo have been developed to target PD-1, while drugs such as Tecentriq lock in on PD-L1.
Dr Lim said he was excited about immunotherapy because its drugs can keep the cancer under control for a relatively long period. It is also usually well tolerated by patients.
Immunotherapy increases long-term survival rates. For patients who try immunotherapy, the five-year survival rate is 16 per cent, compared to 5 per cent for those who did not try immunotherapy.