Yes, some cancers are known to be caused by more than one risk factor (multi-factorial) as given below. Each them may have a summative (additive) effect on an individual giving a higher risk than with those risk factors operating in isolation. Breast cancer: The following increase the risk of breast cancer in women: An age over 50 years, breast cancer in the mother, sisters or daughters, first period before the age of 12 years, menopause after 55 years, never having being pregnant or having first child after the age of 30 years, obesity and oestrogen treatment (hormone treatment post-menopausal symptoms). Gene mutations (changes genetic material) in BRCA1 and BRCA2 genes predispose to breast cancer. The following also seem to increase the predisposition to breast cancer in women: high fat diet, physical inactivity, use of oral contraceptives and consumption of more than one alcohol drink per day. 
Cervical (neck of the womb) cancer: The following increase the risk of cervical cancer: Sexual intercourse at an early age, multiple sexual partners (with the woman or with her partner), genital infections with human papilloma virus, HIV infection and smoking. 
Colorectal cancer: The following increase the risk of colorectal cancer: An age over 50 years, family history of colorectal cancer, personal or family history of large bowel polyps, personal history of inflammatory bowel disease, high fat diet, diet low in fibre, fruit & vegetables, physical inactivity, cigarette smoking, alcohol consumption and obesity. 
Endometrial cancer (uterine cancer): The following increase the risk of endometrial cancer: Increasing age, first period before the age of 12 years, menopause after 55 years, oestrogen treatment (hormone treatment after menopause), never being pregnant and infertility. 
Lung cancer: The commonest cause of lung cancer is smoking. The other factors that are incriminated include exposure to asbestos, radon, arsenic or radiation and air pollution. Passive smoking (second hand exposure) is also known increase the risk of developing lung cancer in non-smokers. 
l Ovarian cancer: The following increase the risk of ovarian cancer: Age over 50 years, ovarian cancer in the mother, sisters or daughters and having never being pregnant. 
Prostate cancer: The following increase the risk of prostate cancer: Age over 50 years, history of prostate cancer in the father, brothers or sons and consumption of diet high in saturated fat, low in fibre, fruits and vegetables. African American men are known to have twice the incidence of prostate cancer compared to white men. 
Skin cancer: The following increase the risk of skin cancer: Exposure to excessive sunlight, excessive exposure to UV light from ‘tanning beds’, fair complexion and family history of skin cancer. Fair people living in sunny climates are more vulnerable to development of skin cancer. In addition, chemicals such as coal tar, pitch, creosote, arsenic and radium are recognised risk factors. 
We hope that the account that you have just read will help to avoid any modifiable risk factors in causation of cancer and equip you to advise your family and friends even in a small way to cut down the risks of developing cancer. Prepared by Professor P L Ariyananda Professor P L Ariyananda MBBS (Cey.), MD (Col.), FRCP (Lond.), DCH (Cey.) Professor in Internal Medicine, International Medical University, Malaysia Emeritus Professor in Medicine, University of Ruhuna, Sri Lanka Adjunct Professor, Duke Global health Institute, Duke University, NC, USA Professor Ariyananda has a special interest in medical education, medical toxicology and in respiratory medicine. He has over seventy publications in medical literature in the form of published abstracts and journal articles at both national and international level. He has authored a book in ‘Pictures in Tropical Medicine’ and co-authored a book in ‘Medical Emergencies’ for medical undergraduates and junior doctors.
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