Understanding personalised treatment and its impact on cancer care
By Dr Allan Njau and Dr Jonathan Wawire
If you have a symptom, or a screening test result that suggests you have cancer, your doctor will order lab and/or imaging tests to confirm that it is indeed cancer and should that be the case, the type of cancer and the stage of the disease will be confirmed. And, beyond confirming the type of cancer, laboratory medicine has grown so much that doctors are able to offer personalised treatment marking critical turning point as far as the traditional, or convectional forms of cancer treatment is concerned.
Surgery is an important element in cancer treatment, this may involve total or partial removal of the cancer. However, not all cancer types are treated using surgery. In addition, in cases where the cancer has spread widely, it may not be safe or possible to operate. Chemotherapy on the other hand, typically involves a combination of drugs which kill the cancer cells given before and/or after surgery or even without surgery. Radiotherapy uses high energy radiation to kill the cancer cells. Surgery, chemotherapy and radiotherapy are often combined. The use of chemotherapy and radiotherapy may be limited by the fact that normal, non-cancerous cells are normally affected or even killed in the process. What is important, though, is personalised medicine in the context of cancer.
Personalized medicine, or in other words, precision medicine, involves formulating disease treatment or prevention plans while considering the differences in individuals which may be determined by their genes, lifestyles and the abnormal genes that initiate, or drive cancer growth in a particular person. The aim is to find the best available treatment at the right time, for the right individual.
Put simply; individuals are not the same, cancers are not the same, hence treatment should not be the same for each patient even with the same type of cancer. Some of the benefits of personalised medicine include, fewer side effects, greater efficacy, meaning better treatment outcome and better quality of life. In many cases, there is no clarity between personalised medicine and targeted therapy.
Targeted therapy falls under personalized medicine. In targeted cancer therapy, uniquely designed drugs, hormones or antibodies are used to block the genes or proteins “molecular targets” that drive cancer growth and spread.
Eligibility for targeted therapy
Depending on the type of cancer, stage, recurrence status of cancer or failed standard “chemo” or “radio” – therapy, your oncologist may recommend molecular test(s) on the cancer tissue or blood to analyses the status of the “molecular targets” for which targeted therapy, hormones or drugs may be applied. We generally call these molecules or molecular targets, biomarkers. The biomarkers can be used for diagnosis of a particular type of cancer, they can be prognostic, meaning that they are used to predict the biologic behavior and aggressiveness of the cancer, or they can be predictive, which has to do with predicting or identifying the therapy that would be best for that type of cancer.
Patients who cannot tolerate “chemo” or “radio” due to underlying conditions, side effects, or age, can benefit from personalized therapy. The molecular tests are conducted by pathologists who have specialised in this area, supported by requisite equipment. This testing is available in Kenya including at Aga Khan University Hospital, Nairobi. Some of the advanced tests however are outsourced to other laboratories outside the country.
Examples that are already in clinical use
Take an example of a patient with colon cancer which advances with metastasis (meaning that the cancer has spread to a different body part from where it started), despite several regimens of chemotherapy. We know that colon cancer is driven by an abnormal growth pathway called Epidermal Growth Factor Receptor pathway (EGFR). Therefore, blocking this pathway with a specific drug in combination with chemotherapy, results in better anti-cancer effect. Prior to administration of these drugs molecular testing for presence or absence of mutations of key genes which drive cancer growth is performed to predict which patients would have maximum benefit or response. Multiple other cancer including breast cancer, lung, melanoma, pancreatic and renal cancer are amenable to targeted therapy.
What about immunotherapy?
The body’s immune system is a powerful weapon to fight cancer. However, some cancer cells produce molecules which suppress the immune system. Testing for these immune suppressive molecules allows doctors to harness your own immune system to fight cancer by giving drugs that frustrate cancer cells. Again this testing is done by pathology specialists with access to the right equipment.
An example is the treatment of advanced esophageal, gastric cancer and cancer of the cervix, which have a high prevalence in Kenya. Testing to identify whether cancer cells are producing immune suppressing molecules such as programmed death-ligand 1 (PD-L1) is performed. Cancer cells that produce such molecules can be targeted by blocking these molecules, and thus enabling your immune system to attack the cancer cells. But what benefits of molecular testing?
Some of the molecular tests are useful for screening relatives of cancer patients in families with strong history of cancer. This facilitates early screening, diagnosis and treatment increasing the chances for cure. An example is BRCA 1 and 2 gene testing for hereditary breast and ovarian cancer syndromes.
At the moment, targeted therapies are not widely accessible, and although the cost is dropping with the passage of time, they are expensive. Patients on targeted therapy may also suffer from various side effects, although they are usually less severe that chemotherapy. Targeted therapies are therefore not a magic bullet for cancer, since complete cures are difficult in advanced cancer. Therefore, even with emerging therapies for cancer, we cannot over emphasize the importance of screening, early diagnosis and treatment. – Dr Njau and Wawire are Molecular Pathologist and Anatomical Pathologist, respectively, at Aga Khan University Hospital, Nairobi.