Lung cancer is one of the most common types of cancer affecting people in Thailand and across the world. Lung cancer also poses the highest risk of death of any cancer, causing 1.69 million deaths annually, which is more than breast cancer, colon cancer, and prostate cancer combined.
Targeted Therapy as Treatment for Lung Cancer
Generally, cancer is treated in one of the following ways: by surgery (when possible), by radiation treatment, by chemotherapy medicine, or by a combination of multiple methods of treatment to prevent the spread and growth of the cancer cells.
Cancer treatment through chemotherapy medicine can result in adverse side affects in some people. This is because the medicine may sometimes start to attack healthy cells as well as the cancer cells.
To prevent this, a new type of treatment which specifically targets only cancer cells has been developed, known as targeted therapy. This form of treatment restricts the specific cell-signaling process which causes the growth of cancer cells, while also separating the cancer cells and having as little effect on regular cells as possible. This means that there are significantly fewer side-effects resulting from targeted therapy when compared with chemotherapy medicine.
Aside from lung cancer, targeted therapy is used to treat a variety of different cancer types, such as liver cancer, kidney cancer, colon cancer, breast cancer, ovarian cancer, head and neck cancer, and lymphoma.
Gene Mutation with Anti-Cancer Medication
When we talk about targeted therapy for lung cancer, we are usually talking about non-small cell lung cancer, as this type of lung cancer is the most common. Non-small cell cancer accounts for around 85-90% of lung cancer cases, and is considered less severe due to the more developed treatment methods available, while small cell lung cancer accounts for only 10-15% of lung cancer conditions. Currently, there are research and development programs aimed at medicine to treat non-small cell cancer conditions, while small cell lung cancer is still in the early stages of medication development as it has only been discovered within the last two years.
Lung cancer has many causes, such as smoking, exposure to toxins, age, and family history. Targeted therapy is specifically for those whose cancer is caused by particular genetic alterations, for example:
- Epidermal Growth Factor Receptor (EGFR) Gene: This is the most common mutating gene found in cancer patients, with 10% of people with general lung cancer having this gene. It is also found in 50% of non-smokers with lung cancer in Asia. This gene stimulates the signal that causes cancer cells to spread and grow. Targeted therapy medicine for the EGFR gene (anti-EGFR drugs) include erlotinib, afatinib, gefitinib, and osimertinib, which are all in tablet form to be taken orally.
- Anaplastic Lymphoma Kinase (ALK) Gene: This gene is less common and accounts for only 5% of the gene mutations found most commonly in non-smokers. This gene’s mutation causes cancer cells to grow and spread. Drugs that target and block the ALK gene are crizotinib, ceritinib, brigatinib, and alectinib, all of which are most commonly found in tablet form to be taken orally.
There are some other types of mutating genes which are known to be related to causing lung cancer. However, these are very rare. They include, for example, the BRAF gene and ROS1 gene. There are many other types of cancer-causing genes that are yet to be discovered, which is all part of the continuous research process of finding causes and developing new medicines and treatments.
Therefore, whenever a patient has a mutating gene discovered, the doctor will choose to prescribe the appropriate medicine for that gene in order to suppress the spread of the cancer, and to provide the most effective treatment possible, while reducing the side-effects to an absolute minimum.
Type and Function of Medicine
There are two types of drugs used for targeted therapy, each with different effects. These are:
- 1Monoclonal antibodies: This type of medicine acts by attaching to the targeted area on the outside of the cancer cell and subsequently preventing any growth or development of the cancer. This medicine is commonly administered intravenously and used together with chemotherapy.
- Small molecules: The medicine in this category is able to enter the cancer cell membrane to prevent any growth or spread of cancer. Usually in tablet form, to be taken orally, this type of medicine includes erlotinib and gefitinib for the EGFR gene and crizotinib for the ALK gene.
Side Effects of Targeted Therapy
Although the medicines for targeted therapy have significantly reduced side-effects in comparison to chemotherapy medicines, there are still some side-effects which may be experienced, such rashes, dry skin, diarrhea, nausea, vomiting and exhaustion. The patient’s doctors should be notified immediately if any of these side-effects arise.
The results of a patient survey on anti-EGFR and anti-ALK medication showed that 60%-70% of patients experienced no unusual symptoms, while their life-expectancy was increased and their quality of life improved.