Why is breast cancer common but heart cancer rare?

The researchers suggest that this vulnerability of some organs may be due to natural selection.

Humans are more likely to carry tumours in large or paired organs than in small, critical organs such as the heart, and so larger organs may have developed fewer mechanisms to protect themselves against cancer cells.

The organs that are most important in keeping you alive and able to reproduce, such as the heart, brain or uterus, may have the best defences against cancer, all else being equal,' said Frédéric Thomas, an evolutionary biologist at the Centre for Ecological and Evolutionary Cancer Research in France. - We are not saying that this is the main factor explaining the different susceptibility of organs to cancer, but it is a factor that contributes along with the others.

Many oncologists have explained differences in organ cancer incidence by looking at either external risk factors, such as smoking or exposure to ultraviolet light, or internal factors, such as the frequency of cell division in an organ.

Thomas and his co-authors, including senior author Beata Uiwari, an evolutionary ecologist at Deakin University in Australia, propose this evolutionary theory to add to current understanding.

The team suggests that natural selection has favoured strong anti-cancer protection for small organs that are critical for human survival and reproduction.

Organs that are large or paired can potentially accumulate more oncogenic manifestations without compromising function, whereas small and important organs, such as the pancreas, can easily become dysfunctional with just a few tumours inside, says Thomas.

So, according to this theory, the pancreas should be better protected against cancer than an organ such as the kidney, if all other factors are equal. The mechanisms of protection against cancer differ from organ to organ, but in general they make the organ resistant to tumour formation.

The researchers also recommend that cancer biologists consider individual organs as specialised islands with their own environmental conditions (such as oxygen levels, acidity or water), where the survival of cancer cells depends on the hospitality of the local environment.

Malignant cells are living entities - it is simply impossible that they are not affected by environmental conditions," says Thomas. - This clearly indicates that some organs are more favourable to malignancy than others.

We have compiled a list of the organs most vulnerable to cancer, according to oncologists, medical professionals who specialise in diagnosing and treating cancer.

• Breast

Breast cancer is the most common type of cancer among women worldwide. This prevalence is partly due to the dense and complex structure of the breast, which consists of numerous glandular tissues that are sensitive to hormonal changes. These tissues can undergo abnormal changes leading to cancer, especially under the influence of risk factors such as genetic predisposition, age, certain hormonal therapies and lifestyle, including diet, physical activity and alcohol consumption.

• Lung

Lung cancer, including non-small cell and small cell lung cancer, is one of the leading causes of cancer deaths worldwide. The lung's high vulnerability to cancer is primarily due to environmental factors, particularly tobacco smoke. Cigarette smoking introduces various carcinogens into the lungs, causing DNA damage in lung cells and subsequent cancer development. Exposure to radon, asbestos and some other occupational or environmental pollutants may also increase the risk of lung cancer.

• Prostate

The prostate gland is very prone to cancer, particularly in older people. Prostate cancer usually develops slowly and may not cause any symptoms or problems for many years. Risk factors for prostate cancer include age, heredity, race and certain eating habits. The reason why the prostate gland is susceptible to cancer is not entirely clear, but may include hormonal influences and specific cellular properties of the prostate gland.

• Colorectal

Colorectal cancer, including colorectal and rectal cancer, is a major health problem worldwide. The main function of the large intestine is to process waste, which means it is regularly exposed to a variety of foods and bacteria that may contribute to the development of cancer. Risk factors for colorectal cancer include age, a diet poor in fibre and rich in fat and calories, a sedentary lifestyle, alcohol consumption, smoking, and some hereditary conditions.

• Skin

Skin cancer is one of the most commonly diagnosed cancers in the world, mainly due to direct and frequent exposure of the skin to ultraviolet (UV) radiation from the sun or artificial sources, such as tanning beds. There are several types of skin cancer, including basal cell carcinoma, squamous cell carcinoma and melanoma. The vulnerability of the skin to cancer highlights the importance of protective measures such as using sunscreen, wearing protective clothing and avoiding sunbeds.

Conclusion

Understanding which organs are most vulnerable to cancer can help guide prevention efforts and determine screening recommendations. It is important to note that although these organs are statistically more susceptible to cancer, malignancies can appear anywhere in the body. Therefore, maintaining a healthy lifestyle, including regular exercise, eating a balanced diet, avoiding tobacco and excessive alcohol consumption, and getting the recommended screenings, is essential to minimise your overall risk of cancer. As always, regular medical check-ups and discussions with health care professionals are key to early detection and effective treatment.