While immunotherapy has its roots in China’s Qin dynasty period, it is only recently used to treat cancer, where drugs are used to enhance the immune system to recognize and destroy cancer cells. Indeed, our immune system has a built-in anti-tumour activity through specific immune cells (e.g., natural killer cells, macrophages, and T-cells), which recognize cancer cells as foreign entities and initiate killing. For this reason, cancers have evolved mechanisms to turn off such immune system activities as they are growing into a tumour. So, certain immunomodulators have been developed to stimulate the antitumor immune system.
For example, Sipuleucel-T cancer vaccine has been approved to treat metastatic prostate cancers resistant to hormonal therapy. This immunotherapy stimulates T-cells (i.e., a type of white blood cell) to attack cancer, acting similarly as vaccines that train the immune system against infectious diseases. Pembrolizumab, a so-called check-point inhibitor, is another approved immunomodulator used for advanced prostate and breast cancers with certain mutations. Several antibody-based drugs have also been approved for breast cancers, although each has their suitability designed for specific cancers subtypes.
The advent of immunotherapy offers hope for hard-to-treat cancers that are resistant to other forms of therapy. As everyone has an immune system, immunotherapy can be designed to fight all sorts of cancers. Indeed, the list of cancers treatable with immunotherapy is vast. Furthermore, this therapy can train the antitumor immune system for the long-term; hence, providing sustained clinical benefit and lowering cancer recurrence risks. Immunotherapy can also complement other therapies to augment overall efficacy. Unfortunately, no treatment is perfect, and immunotherapy also has its limitations:
#1. Most immunotherapy only suits certain types of cancers or patients. This is because immune responses can vary in every cancer and person, so immunotherapy must be more personalized; thus, its utility may be limited.
#2. Immune reactions induced by immunotherapy can bring side effects, such as chills, fever, headache, fatigue, joint pain, diarrhea, heart palpitations, swelling and fluid retention.
#3. Immunotherapy regimens may take longer than other cancer therapies to work, so multiple clinical visits are required over a long duration.
#4. Immunotherapy outcomes can be unpredictable as immunotherapy may be incompatible with the immune system of certain individuals. In rare cases, including prostate and breast cancers, life-threatening autoimmune reactions can happen, where the immune system starts attacking the patient’s own organs.
#5. Sometimes, immunotherapy can be ineffective for many reasons. For one, the tumour can strengthen its immunosuppressive activities to resist immunotherapy. Plus, cancer cells from an individual may not be recognized as foreign by the immune system. Some people may already have a weaker immune system due to old age, underlying medical conditions or prior toxic chemotherapy, which invariably destroys many of the patient’s immune cells, so immunotherapy cannot recruit and stimulate enough immune cells to mount anti-cancer effects.
Therefore, the following should be considered before recommending immunotherapy: Although this treatment modality has certainly brought benefits to some cancer patients, it requires a highly personalized approach supervised by an experienced medical specialist at all times. Interestingly, immunotherapy also introduces the potential of immune-boosting natural products. For example, IMUSAN, a mixture of 13 medicinal herb extracts that has been shown to exert anti-metastatic efficacy associated with NK and T-cell stimulation, or Aeskulap-MCP, a modified citrus pectin, as well as BioBran, an arabinoxylan extracted from rice bran, all of which provide benefits to cancer patients as immune modulators.
