What are the conventional Cancer therapies?
When Cancer is diagnosed, one of the three conventional therapies is usually administered: Chemotherapy, Surgery, or Radiotherapy. [1] In some cases, other treatments are used, such as immunotherapy or targeted therapies, but these are used less often than conventional therapies.
Chemotherapy was historically the mainstay of Cancer treatment [2]. There are different types of chemotherapy drugs, but they all generally work by targeting the rapidly dividing cells [3] (Cancer cells divide more rapidly compared to normal tissues) and disrupting various mechanisms responsible for cell division. These include DNA damage, disrupting DNA replication and synthesis and interfering with cell parts that take part in cell division. This kills some cells and prevents others from replication. [2] However, chemotherapy is a double-edged sword, as it is also associated with toxicities that range in severity. One of the most visible ones is the hair loss. This is because the cells in the hair roots are rapidly dividing, so they get targeted by chemotherapy [3]. Other toxicities include kidney, liver, nerve system and heart toxicities. [4] Additionally, a decrease in immune cells and platelets can occur, as well as gastro-internal tract toxicities, which include nausea and diarrhoea. [5] Additionally, Cancer can develop resistance to chemotherapy, which adversely impacts the treatment in the long term. [6] After hearing the side effects, the chemotherapy might look scary. However, it is important not to forget about the survival benefits in many Cancers that chemotherapy brings and that if it is prescribed, then its benefits outweigh its risks.
Radiotherapy is administered for more than 50% of patients [7]. Radiotherapy aims to locally cure the tumour (at the site of its origin) without severe side effects. X and Gamma rays are usually used during radiotherapy because they are high-energy waves (carry much energy). In simple terms, when these rays go through a medium, they can collide with electrons, transferring part of their energy to them and knocking them from the atoms. This is called ionisation and ultimately leads to DNA damage (ionisation usually makes affected atoms more reactive, which in turn damages DNA), leading to the Cancer cell losing its ability to replicate and eventually dying. However, it is important to remember that these rays penetrate healthy tissue. The radiotherapy can be administered in fractions to minimise damage to healthy tissues. This is called fractionated radiotherapy, and it works by delivering small doses of radiation over multiple sessions, allowing the healthy cells to heal and making Cancer cells more susceptible to the therapy. The radiation can be delivered externally (a machine shoots beams at the tumour) or internally (a radioactive element is placed inside the body near the tumour). [8] Just as chemotherapy, radiotherapy can damage healthy cells, leading to various side effects that differ based on the organ treated. The most common side effects are fatigue, diarrhoea, hair loss and skin damage. Additionally, the organ treated can experience problems with functioning (such as problems with memory if brain Cancer is treated). [9]
Surgery has been a mainstay for the treatment of solid Cancers. [10] It involves surgical removal of the tumour and some of the healthy tissue around it to ensure that no Cancer cells are left. However, not all tumours are fully resectable (can be removed through surgery), as the tumour might be at a place where it is very hard to remove (or is near delicate tissue), and surgery might be performed to remove the bulk of the tumour. [11] There are different types of surgeries that can be performed, some including surgery using robotic machines and keyhole surgery (removal of Cancer through a series of tiny cuts). One of the disadvantages of the surgery as a treatment is that it does not work for liquid tumours, such as leukaemia (blood Cancer), as those are usually spread around the body. [12] Additionally, surgery can lead to pain in the area of surgical intervention, infections and blood clots. Some other side effects vary depending on the organ on which the operation was performed. [13]
These are the three mainstays of Cancer treatment. They are widely used to treat many tumours. However, in the last decades, there has been a shift towards new, targeted immunotherapies, but this is a story for another post.
References:
www.cancer.gov. (2011). https://www.cancer.gov/publications/dictionaries/cancer-terms/def/conventional-treatment#. [online] Available at: https://www.cancer.gov/publications/dictionaries/cancer-terms/def/conventional-treatment#.
Tilsed, C.M., Fisher, S.A., Nowak, A.K., Lake, R.A. and Lesterhuis, W.J. (2022). Cancer chemotherapy: insights into cellular and tumor microenvironmental mechanisms of action. Frontiers in Oncology, 12, p.960317. doi:https://doi.org/10.3389/fonc.2022.960317.
Mayo Clinic Staff (2022). What to expect about hair loss during chemo. [online] Mayo Clinic. Available at: https://www.mayoclinic.org/tests-procedures/chemotherapy/in-depth/hair-loss/art-20046920.
Van den Boogaard, W.M.C., Komninos, D.S.J. and Vermeij, W.P. (2022). Chemotherapy Side-Effects: Not All DNA Damage Is Equal. Cancers, 14(3), p.627. doi:https://doi.org/10.3390/cancers14030627.
Cancer Research UK (2020). About Side Effects of Chemotherapy | Cancer in General | Cancer Research UK. [online] www.cancerresearchuk.org. Available at: https://www.cancerresearchuk.org/about-cancer/treatment/chemotherapy/side-effects/about.
Ramos, A., Sadeghi, S. and Tabatabaeian, H. (2021). Battling Chemoresistance in Cancer: Root Causes and Strategies to Uproot Them. International Journal of Molecular Sciences, 22(17), p.9451. doi:https://doi.org/10.3390/ijms22179451.
Carlos-Reyes, A., Muñiz-Lino, M.A., Romero-Garcia, S., López-Camarillo, C. and Hernández-de la Cruz, O.N. (2021). Biological Adaptations of Tumor Cells to Radiation Therapy. Frontiers in Oncology, 11. doi:https://doi.org/10.3389/fonc.2021.718636.
Mehta, S., Suhag, V., Semwal, M. and Sharma, N. (2010). Radiotherapy: Basic Concepts and Recent Advances. Medical Journal, Armed Forces India, [online] 66(2), pp.158–162. doi:https://doi.org/10.1016/S0377-1237(10)80132-7.
National Cancer Institute (2022). Radiation Therapy Side Effects. [online] National Cancer Institute. Available at: https://www.cancer.gov/about-cancer/treatment/types/radiation-therapy/side-effects.
Coffey, J., Wang, J., Smith, M., Bouchier-Hayes, D., Cotter, T. and Redmond, H. (2003). Excisional surgery for cancer cure: therapy at a cost. The Lancet Oncology, [online] 4(12), pp.760–768. doi:https://doi.org/10.1016/S1470-2045(03)01282-8.
Lee, S. (2011). Surgery in cancer treatment. [online] Canadian Cancer Society. Available at: https://cancer.ca/en/treatments/treatment-types/surgery.
Cancer Research UK (2022). What is cancer surgery? | Cancer Research UK. [online] www.cancerresearchuk.org. Available at: https://www.cancerresearchuk.org/about-cancer/treatment/surgery/about.
Cancer Research UK (n.d.). Possible problems after cancer surgery | Cancer Research UK. [online] www.cancerresearchuk.org. Available at: https://www.cancerresearchuk.org/about-cancer/treatment/surgery/long-term-problems.
