Introduction

Prostate cancer, as the name implies, is a malignancy of the prostate gland. The prostate gland is a walnut-sized organ that is situated between the penis and the bladder in the male reproductive system.³ Although it has been widely known to be associated with the production of semen, there is still so much to learn about its complete range of functions, and how it interacts with the hormones to modulate male reproduction. It is unsurprising, therefore, that there is yet a lot to understand about how this cancer develops.

Although its incidence is highly variable across the regions of the world, prostate cancer is the second most common cancer in men, after lung cancer, and the fifth leading cause of death worldwide¹. In 2018 alone, over 1.2 million cases were newly diagnosed, with prevalence rates higher in developed countries than in countries of Asia and Africa.^1,2,3

It is largely a slowly growing cancer, showing no signs or symptoms for so many years in its course, and largely associated with advancing age.^2,3 Its symptoms are also non-specific including an increased urge to urinate, straining and feeling of incomplete voiding.³ 

The reasons behind prostate cancer development are complex, even to seasoned researchers. This complexity leaves men around the world with questions about their predispositions to prostate cancer, especially because these risks differ from person to person. The goal of this article is to carefully outline these causes- from common to emerging, to provide a more concise and understandable insight.

Causes of prostate cancer

Like several other cancers, its exact cause is largely unknown, rather, its occurrence is associated with a wide range of risk factors which vary from person to person.^2,3 These risk factors may be non-modifiable such as individual genetics, family history, and age, or modifiable like diet, smoking and alcohol.^1,2,3 Similarly, some emerging factors have been reported to be linked to prostate cancer and these are currently being investigated in the medical field.

Genetic factors and family history

Many genes have been linked to the development of prostate cancer. Some of them include:

• HPC1: A mutation in an enzyme this gene instructs (RNASEL) compromises the immune system’s defence against a certain virus called retrovirus which has been implicated in the occurrence of prostate cancer^1,2
• HPC2/ELAC2: Although its mechanism is not well understood, this gene is believed to be associated with promoting conditions that allow cancer cells to grow more rapidly¹
• MSR1: While this gene is linked to prostate cancer, it has been found to have a low impact on an individual’s risk¹
• BRCA1 and BRCA2: A mutation in these genes is linked to a more aggressive prostate cancer.^1,2 It is also believed that when a person has the BRCA2 gene mutation, they have a higher risk of prostate cancer, and this genetic mutation has been found to run in families
• X Chromosome: The X chromosome plays a role in prostate cancer inheritance.^1,2 It is important to note that although a man with a brother or father with prostate cancer has an increased risk of developing the disease, shared genes are not the only factors at play.¹ They may have the same exposure to cancer-causing environmental or lifestyle factors

Environmental factors

Exposure to chemicals and toxins

Herbicides, insecticides, and synthetic compounds used in the manufacture of plastics such as for bottles have been associated with cancer development including prostate cancer.^1,2

Diet

Diet significantly impacts prostate cancer development, as seen when immigrants from developing countries (low-risk areas) migrate to industrialised countries and adopt a Westernised diet, leading to increased prostate cancer rates among them.¹ High intake of saturated animal fat, corn oil, red meat, calcium, milk, cheese, vitamin D deficiency, and high blood folate levels are all associated with the development of prostate cancer.^1,2,3

Conversely, the consumption of vegetables such as broccoli, Brussels sprouts, cauliflower, cabbage, and turnips is protective against prostate cancer development.^1,2 Other protective food substances include tomatoes, soy, green tea, vitamins D and E, and selenium. It has also been found that coffee consumption lowers the risk of developing aggressive and advanced prostate cancer.¹

Lifestyle choices (Smoking and Alcohol Consumption)

Having more than three drinks of wine, liquors or beer may be a risk factor for prostate cancer, although evidence is weak in linking alcohol consumption with prostate cancer mortality.^1,2,3 Similarly, both active and passive cigarette smoking are associated with a lot of cancers including cancer of the prostate.

Hormonal factors

Sex hormones

The male sex hormones are implicated in prostate cancer development. To support this, studies on this subject noted that in castrated males or those on therapy to counteract the male hormones, there was a proven improvement in recovery among prostate cancer patients.^1,2 On the contrary, other researchers believe that male sex hormones are usually low among prostate cancer patients, highlighting that oestrogen might be the culprit in the development of prostate cancer.¹

Hormonal Imbalances (e.g. Insulin and Insulin-Like Growth Factor)

Insulin and insulin-like growth factor (IGF) generally maintain the balance of sugar in the blood and body cells.^1,2 The question of how high sugar levels are linked to prostate cancer is still controversial as some scientists believe it increases the risk of prostate cancer while others believe otherwise.

Age and demographic factors

Older men

Prostate cancer is generally associated with senior men, usually 50 years of age in White men with no family history of the disease and 40 years in Black men or men with a history of familial prostate cancer.² Because of how slowly this cancer progresses, many prostate cancer diagnoses have been made upon autopsy.¹ It is unsurprising to hear that some prostate cancer patients are more likely to die from other concomitant chronic diseases than from prostate cancer.

Race and ethnicity

Using the different racial groups in the US as an example, prostate cancer is highest among African-American men and lowest among American Indian/Alaska Native and Asian/Pacific islander men.¹ This disparity is associated with socioeconomic factors, the quality of healthcare available to the different racial groups, access to prostate cancer screening services, and genetic factors. African-American men also tend to have more aggressive forms of prostate cancer, potentially due to genetic differences and lower rates of screening and early detection.

Medical conditions and medications

Existing medical conditions (Obesity and Inflammation)

Exercise and physical activity are among the easiest modifiable factors that prevent prostate cancer.^1,2,3 This is because obesity and high BMI levels are linked to higher hormonal imbalances such as insulin, as well as higher Prostate-Specific Antigen (PSA) levels in the body. Fat cells also pose a source of inflammation which releases certain chemicals in the body that predispose to cancer.¹ In addition to the increased risk of cancer, obesity is linked to more aggressive disease and higher death rates.

Sexually transmitted disease (STD)

There is growing evidence that previous or current sexually transmitted infections are associated with prostate cancer.¹ Bacterial infections like gonorrhoea and syphilis have been found to cause inflammation of the prostate, while viruses like herpes (Herpes Simplex Virus, HSV) and HPV have been found to use their ability to transform themselves in human cells leading to those pathways that cascade into prostate cancer development. Even parasitic STIs have been linked to the development of prostate cancer.

Controversial and emerging causes

Long-term use of certain medications (E.g., Anabolic Steroids)

It is thought that certain drugs such as anabolic steroids might lead to an increased risk of prostate cancer.¹ There is barely sufficient evidence for this submission as the mechanism is not well established.

Debated causes (E.g., Viral infections, Vasectomy)

Some rather interesting risk factors have been considered in the prostate cancer discourse. For instance, there is an ongoing debate regarding the role of vasectomy in the occurrence of prostate cancer.¹ Some authors argue that it poses an increased risk while others believe it is protective against prostate cancer.

Sexual intercourse

It is yet to be conclusively determined if a higher frequency of ejaculation protects against prostate cancer or if it leads to wear and tear which may predispose a man to prostate cancer.¹

Prevention and early detection

Strategies based on known causes

Based on the established prostate cancer risk factors, many strategies can be adopted to prevent prostate cancer. These are as follows.

1. Lifestyle modifications: individuals can adopt diets rich in fruits, vegetables, and antioxidant micronutrients that are protective against prostate cancer.^1,2,3 In addition, more physical activity and moderate exercise can be adopted
2. Consult your doctor to treat underlying medical conditions such as high cholesterol^1,3

Regular screening and early detection methods

1. Personalised risk assessment: Consult your doctor for a personalised risk assessment, to identify both modifiable and non-modifiable risk factors you may have and come up with a prevention plan¹
2. Early screening: The commonest is the PSA screening and monitoring, which is helpful but unreliable as many conditions could cause its increase.^1,2,3 A normal level does not exclude prostate cancer either. PSA testing is usually accompanied by risk assessment, symptom review, and a prostate examination at the hospital.³ Depending on the outcome, an MRI scan or biopsy might be requested to confirm any suspicions
3. Prompt treatment: If the cancer is caught early, a patient may be placed on watchful waiting with close monitoring without significant medical or surgical intervention.³ For some, surgery to remove the prostate gland may be curative in addition to medications. Some patients may also require radiotherapy or hormonal therapy in addition to some of the treatment modalities. In advanced disease, a more conservative approach to management is preferred

Summary

In conclusion, understanding the causes of prostate cancer is crucial for every man’s health journey. From genetics to lifestyle, and even the foods we eat, multiple factors can influence our risk of developing this common yet serious disease. While some risks, like our age and family history, are beyond our control, knowledge empowers us to make informed decisions about our health.

Regular screenings and a proactive approach to maintaining a healthy lifestyle can significantly aid in early detection and prevention. As research unveils new insights, staying informed and vigilant is the best defence against prostate cancer.