I will start off this blog with a brief note on a new direction for cancer treatment: cancer immunotherapy. Briefly, common treatments for cancer use a combination of surgery, radiation therapy and chemotherapy to remove or shrink a tumor. But, a key problem for cancer treatment is the recurrence of tumor formation months or years after the primary tumor has been removed. Why does this happen?
Due primarily to the inability to remove all cancer cells after the initial round of treatments. Specifically, if the tumor is found in an accessible area such as the liver or lung, the affected part would be completely removed by surgery followed by chemotherapy to kill remaining cancerous cells. However, cancer cells are living cells capable of adapting to their surrounding conditions (i.e., high doses of chemotherapy drugs) and evolving new strategies to defeat the main mechanism that cancer drugs used to kill them, for example, causing the cell to enter a cell death program (or apoptosis). This process of evolution of counter strategies aimed to prolong the survival of individual cancer cell is known as resistance, and is the main reason why cancer recurs. Together with the phenomenon of metastasis, where cancer cells from a primary tumor migrate, through the bloodstream, to a new site and establish a new tumor growth area, the second round of cancer occurrence can be more devastating than the prior one, and commonly kill the patient.
Thus, what is cancer immunotherapy and what does it brings to cancer treatment? The main reason for large amount of efforts dedicated at cancer immunotherapy research arises from the significant side effects of cancer chemotherapy such as fatigue, weight loss, and most visibly, loss of hair. Cancer immunotherapy, in principle, harnesses the ability of the immune system to identify and kill cancer cells; thus, they are more targeted compared to chemotherapy drugs in killing cancer cells. With good cells spared, the body is better able to ward off the effect of cancerous growth on the body. The immune system, however, is understandably weaker after cancer occurrence, and thus, requires a boost to fight cancer cells.
In general, there are two main approaches of cancer immunotherapy: inhibitors that release the break on the growth of immune cells that kill cancer cells, as well as infusion of genetically engineered immune cells originally derived from the patient to destroy cancerous cells in the body, in what is known as cell-based therapy. Both approaches are relatively new, and although drugs that use immunotherapy methodology to treat cancer exist, they are still in clinical trials.
In the case of inhibitors, the release of growth brakes on immune cells capable of killing cancer cells may have untoward side effects such as an uncontrolled expansion of immune cells (without growth brake) that result in another cancer, for example, leukemia. On the other hand, public acceptance for direct infusion of patient derived but genetically engineered immune cells for cancer treatment is also a big question mark, and is an area where significant public education is needed.
Finally, cancer immunotherapy is certainly one area to help cancer patients defeat the disease in a more thorough way given the specificity in which immune cells is able to recognize cancer cells compared to chemotherapy drugs that cause significant side effects due to off-target effects, where they also kill normal healthy cells (the visible symptoms of which is the loss of hair common in patients undergoing chemotherapy). However, given its experimental nature and the fact that many of the immunotherapy drugs are still in clinical trials or in the research labs, the mainstay of cancer treatment remains surgery, radiation therapy and chemotherapy.