28 September 2023
Check Up #18 - Side effects of cancer treatments. Can we classify them?
Side effects, long-term side effects, late effects and sequelae of cancer treatments. What distinguishes them?
A side-effect “is any effect of a drug, chemical, or other medicine that is in addition to its intended effect, especially an effect that is harmful or unpleasant”.
We are all familiar with common side-effects of cancer treatments such as nausea, vomiting, fatigue or hair loss. Nausea and vomiting stop and hair grows back once the treatment ends. On the other hand, fatigue can be long-lasting. Moreover, the type of side-effect depends on the type of cancer and the person being treated.
Side-effects are not only physical; they can also be emotional. Cancer survivors may feel depressed, anxious, alone, and may even experience post-traumatic stress disorder, as cancer diagnosis and therapy are traumatic life events.
In fact, there are important differences in the time of onset, duration, severity and chronic damage from side-effects caused by chemotherapy, radiotherapy, surgery and other cancer treatments. Let’s try to sort them out.
As we already mentioned, some side-effects resolve when the treatment ends, but others last longer. A cancer survivor who develops a side-effect during treatment that does not resolve when the treatment ends and can persist over time is said to be experiencing a long-term side-effect.
Fatigue – that constant feeling of physical, emotional and mental tiredness and the most common side effect of cancer treatment – is a good example of a long-term side-effect.
When side-effects appear months or even years after the treatment ends, they are termed late side-effects. For example, either chemotherapy or radiotherapy can cause various late side-effects, such as dental problems, early menopause, hearing loss, heart problems, increased risk of other cancers, infertility, loss of taste, nerve damage, memory issues, osteoporosis, digestive problems, among others.
In fact, secondary cancers or new primary cancers may develop as a late effect of previous cancer treatments or due to the original cancer having spread to other parts of the body (when the treatment leaves some of the cancer cells behind).
As for radiotherapy, it can induce a diversity of side-effects, including long-term and late side-effects, such as permanent loss of saliva, dental caries, impaired wound healing, skin changes and skin cancer, lymphedema, hypothyroidism, lightheadedness, dizziness, headaches, etc.. Another long-term side effect of radiotherapy is that it increases the risk of stroke due to high doses of radiation to the brain.
Both chemotherapy and radiotherapy can also damage bone marrow stem cells, increasing the risk of acute leukaemia or other blood cancers. Damage to the nerves outside the brain and spinal cord, known as peripheral neuropathy, is another long-term side effect of these treatments.
When side-effects cause more profound damage to an organ or bodily system, these are termed sequelae. In the case of prostate cancer, for instance, common and well-known sequelae of surgery are urinary incontinence and erectile dysfunction.
Sources:
https://www.yalemedicine.org/
https://www.cancer.org/
https://www.cancer.gov/
https://www.cancer.net/
https://www.e-roj.org/articles/archive.php
https://www.lls.org/
https://www.merckmanuals.com/
