Causes and Risk Factors for Cancer

Risk factors are the inherited or acquired factors that increase the chance of developing cancer in a person. Several epidemiological studies have suggested a number of genetic and environmental factors that may predispose to cancer. A knowledge about them helps us to make necessary lifestyle choices. Most common causes for cancer are Tobacco, Chemical factors, Physical factors, Dietary factors, Obesity and physical activity, Cancer susceptibility syndromes, Viruses, Inflammation.

Risk factors for cancer can be broadly divided in to 2 types. Inherited causes and Acquired Causes. Acquired causes include lifestyle, diet, occupation, addiction related factors that a person acquired in his life, and cancers due to such causes could be prevented to some extent by lifestyle changes. On the other hand, inherited or genetic causes of cancer are due to mutations in genes, called as cancer susceptibility genes, and such cancers are mostly non-preventable.

Acquired Causes/Risk Factors for Cancer



There are 69 different chemicals in a cigarette that are known to cause cancer. 1 in 8 cancer cases are caused by smoking. 1 in 5 deaths are caused by smoking. Different types of cancer caused by smoking are Lung cancer, Mouth, throat, nose and sinuses cancer, Esophageal cancer, Bladder, kidney and ureter cancer, Pancreatic cancer, Stomach cancer, Liver cancer, Cervical cancer, Colorectal cancer, etc.



Besides body weight, alcohol consumption is the best-established dietary risk factor for cancer. If alcohol is consumed, it should be done in moderation. Moderate alcohol consumption refers to 2 drinks per day in men and 1 drink per day in women. Heavy alcohol consumption is 5 or more drinks any day or 15 or more drinks in a week for men, and 4 or more drinks any day or 8 or more drinks in a week for women. The risk of alcohol associated cancers increase with the duration and amount of alcohol intake.

Cancers predisposed with alcohol intake are breast, liver, esophagus, pharynx, oral cavity, larynx, and rectum.

Excessive Calories, Fats and Processed Foods


The most important impact of diet on the risk of cancer is mediated through body weight. Overweight, obesity, and inactivity are major contributors to cancer risk (visceral obesity). Obesity causes increased estrogen synthesis, insulin resistance. And altered adipokine and cytokine production. These factors cause increased angiogenesis, cell proliferation and survival, predisposing to various types of cancer.

Cancers most commonly caused are colorectal cancer, postmenopausal breast cancer, uterine cancer, pancreatic cancer, and gallbladder cancer.

Dietary fat and breast cancer – High dietary fat gets converted to heterocyclic aromatic hydrocarbons that can cause breast cancer. Also, increased obesity may lead to excessive production of estrogen that is carcinogenic for breast tissue. On the other hand, there is an inverse association between monounsaturated fat (eg. Olive oil) and breast cancer.

Dietary fat and colon cancer – High dietary fat causes increased excretion of bile acids which causes ROS mediated DNA damage. Also, heterocyclic aromatic hydrocarbons produced from fat, heme iron in meat and anabolic hormones used for meat production may promote carcinogenesis.

Dietary fat and prostate cancer – Animal fat strongly associated with the incidence of aggressive prostate cancer, and may cause the transition from indolent form to the more lethal form of this malignancy.

To summarize, High intake of animal fat early in adult life may increase the risk of premenopausal breast cancer, increased risk of colorectal cancer. And prostate cancer, particularly the aggressive forms.

Inherited or Genetic Causes/Risk Factors for Cancer

Following are some syndromes implicated in hereditary cancers:

  • BRCA associated Hereditary Breast and Ovarian Cancer Syndromes
  • Lynch syndrome,  Li-Fraumeni syndrome, Cowden syndrome, Peutz-Jeghers syndrome
  • Heriditary Non-Polyposis Colon Cancer or Lynch Syndrome
  • Familial Adenomatous Polyposis Syndrome (FAP)
  • Multiple Endocrine Neoplasia

Genetic Counselling is advised in case there is a strong suspicion of genetic cancer.

Risk Factors for Various Cancer Types

In the following sections, we will discuss the risk factors and causes for most common cancers across the world. Also, we will explain them in detail  with the help of images and videos

Bladder Cancer

bladder cancer risk factors

Following are the risk factors for Bladder Cancer

  • Tobacco/Cigarette smoking
  • Family history
  • Genetic Cancer Predisposition Syndromes
  • Personal History
  • Occupation exposure
  • Previous Treatment
  • Infections
  • Other Factors like chronic irritation of bladder, old age, etc


Breast Cancer

breast cancer risk factors
Breast Cancer Risk Factors

Following are the risk factors for Breast Cancer

  • Advanced Age
  • Early menarche/late menopause
  • Delayed marriage or childbirth
  • Personal History
  • Family history
  • Genetic alterations
  • Dense Breast Tissue
  • Prolonged hormonal replacement therapy
  • History of Radiation therapy to Breast or Chest
  • Obesity
  • Excessive Alcohol Consumption


Colon Cancer

colon cancer risk factors
Colon Cancer Risk Factors

Following are the risk factors for Colon Cancer

  • Family history
  • Genetic Cancer Predisposition Syndromes
  • Personal History
  • Age
  • Lifestyle
  • Diet
  • Drugs


Esophageal Cancer

esophageal cancer risk factors
Esophageal Cancer Risk Factors

Following are the risk factors for Esophageal Cancer

  • Excessive Alcohol Consumption
  • Excessive consumption of hot beverages
  • Gastroesophageal reflux disease (GERD)
  • Industrial/Occupational exposure
  • Achalasia
  • Barrett’s esophagus
  • Older Age
  • Other Factors like obesity, dietary factors, etc


Kidney Cancer

kidney cancer risk factors
Kidney Cancer Risk Factors

Following are the risk factors for Kidney Cancer

  • Tobacco/Cigarette Smoking
  • Obesity
  • Overuse of pain-killers 
  • Industrial/Occupational exposure
  • Kidney failure/Transplant/Dialysis
  • Family history
  • Genetic Cancer Predisposition Syndromes
  • Other Factors


Ovarian Cancer

ovarian cancer risk factors
Ovarian Cancer Risk Factors

Following are the risk factors for Ovary Cancer

  • Early menarche/late menopause
  • Family history
  • Genetic Cancer Predisposition Syndromes
  • Delayed marriage or childbirth
  • Hormonal replacement therapy
  • Endometriosis
  • Obesity
  • Age


Pancreatic Cancer

pancreatic cancer risk factors
Pancreatic Cancer Risk Factors

Following are the risk factors for Pancreatic Cancer

  • Tobacco/Cigarette Smoking
  • Obesity
  • Industrial/Occupational exposure
  • Family history
  • Chronic pancreatitis
  • Diet
  • Genetic Cancer Predisposition Syndromes


Prostate Cancer

prostate cancer risk factors
Prostate Cancer Risk Factors

Following are the risk factors for Prostate Cancer

  • Old Age
  • Family history
  • Genetic alterations
  • Race/ethnicity
  • Overweight or obese males
  • Dietary Factors


Stomach Cancer

stomach cancer risk factors
Stomach Cancer Risk Factors

Following are the risk factors for Stomach Cancer

  • Helicobacter pylori infection
  • Chronic atrophic gastritis
  • Diet
  • Industrial/Occupational exposure
  • Genetic Cancer Predisposition Syndromes
  • Older age


Testicular Cancer

testicular cancer risk factors
Testicular Cancer Risk Factors

Following are the risk factors for Testicular Cancer

  • Cryptorchidism
  • Race and Ethnicity
  • Personal History
  • Family history
  • Genetic Cancer Predisposition Syndromes

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