OncoAfrica

Why Is Cancer So Hard To Treat?

By Fiona Okonjo

Cancer is an old disease. The earliest description of cancer dates back to ancient Egypt around 3000 BC, as documented in the Edwin Smith Papyrus. The authors described eight cases where tumours or ulcers were removed by cauterization and indicate that the disease “has no treatment”.  This view that cancer cannot be treated persists to date, perpetuating fear of the disease thus leading to late diagnoses and poor patient outcome, because people put off seeing a doctor until it is too late.

Now, you may be wondering, “If cancer has been around for so long, how come we have not found a cure yet?” We have eradicated diseases such as smallpox, discovered antibiotics to treat infections, but why is cancer still a problem 5000 years later? The answers to these questions are multifactorial. Let us explore some of the reasons why cancer is so hard to treat, but also why we should remain optimistic.

First, cancer is not a single disease. The term cancer describes more than 200 different diseases, classified according to the site in which they originate e.g. breast, cervical, and pancreas. Based on their organ of origin, cancer is subdivided into different subtypes according to the specific tissue-type, genetic, and molecular characteristics. For example, ductal carcinoma originates in the milk ducts of the breast whereas luminal breast cancer arises from the cells lining the inside of the mammary duct.

Second, various mutations in certain genes can lead to the development of cancer. Mutations can cause cells to grow uncontrollably and often continue to accumulate as the cancer progresses. Mutations breed diversity in cancer, in that individuals with the same cancer type such as breast cancer, may each exhibit a unique set of mutations. This means that a drug that may work for one cancer patient may have no effect on another patient.

Third, cells within a growing tumor are not identical. A tumor is a complex environment made up of different cell types including stem cells, immune cells, endothelial cells, connective tissue cells, and epithelial cells. As the tumour grows, further mutations may appear over time. Thus, treatment may kill one cell type in a tumor whilst other cells continue to grow, allowing the tumour to resist treatment and survive.

Fourth, a majority of cancers develop resistance to treatment. The mutations acquired over time can cause changes in cell behaviour. This means a tumour that was initially responding to treatment may adapt and evade the effects of that treatment. Alternative treatments may be offered where available; however, resistance to the new treatment may eventually develop too.

Fifth, cancer cells acquire new survival mechanisms that give them a competitive growth advantage. Normal cells have mechanisms that repair damaged DNA and prevent cells from growing uncontrollably. These mechanisms are disrupted in cancer cells enabling them to reproduce without limits. Other unique behaviours that cancer cells acquire in order to survive include the capacity to invade other tissues, the ability to escape the immune system, and immortality.

Although it may seem like we are fighting a losing battle when it comes to finding a cure for cancer, it is not all doom and gloom. Thanks to research, cancer survival rates have improved immensely over the years. For example, the probability of a breast cancer patient living beyond ten years post diagnosis is 85%. For lymphoma, the survival rates were only half what they are today. With further research investigating the multifactorial mechanisms through which cancer cells resist treatment, we can create increasingly effective treatments. For example, the discovery of the BRCA1 gene mutation in breast and ovarian cancers has led to the development of screening guidelines to detect and treat these cancers at an early stage.

So, the big question remains “will we ever find a cure for cancer?” The simple answer is, no. We cannot have a single cure for cancer because it is not a single disease and does not have a single cause. However, as our understanding of cancer increases through research, it will enable the development of new and personalised treatments for the 200+ different cancer types that exist.