The majority of people who develop cancer do not develop it because they possess a cancer gene. The most likely cause for the cancer is related to what our body has been exposed to through the years and these carcinogens increase our risk of developing cancers.

At the recent 9^th American Association for Cancer Research (AACR) International Conference of Frontiers in Cancer Prevention Research, researchers from the University of California studied 2265 women with breast cancer (Abstract B88, 8^th Nov 2010). These women, from northern California and Utah, were diagnosed between 1997 and 2000. About 80% had early-stage breast cancer. The study found that women who were current or past smokers were 39% more likely to die from breast cancer when compared to never smokers. As compared to never smokers, the risk of dying from non-breast cancer causes was increased 116% in current or past smokers. Further analysis of the data showed that body mass index (BMI), menopausal status and tumour HER2 status can adversely affect survival in this population of current or past smokers. Being postmenopausal, having a BMI < 25 kg / m² and having HER2-negative tumour will adversely affect breast cancer survival by 47%, 83% and 61%, respectively.

Researchers from Prague in Czech Republic presented their study on 533 female lung cancer patients and 1971 control subjects at the CHEST 2010: American College of Chest Physicians Annual Meeting (Abstract 9365, 2^nd November 2010). Milk and dairy products, vegetables and physical exercise were found to exert protective effects among smokers. None of these factors were protective for non-smokers. However, black tea was found to exert a protective effect on non-smokers.

Although smoking is known to cause cancers, heart and lung diseases, millions and millions of people worldwide are still puffing away. The best way to prevent getting ill health is not to smoke at all. To those smokers who have developed breast or lung cancers, there is still some things you could do to help yourself, albeit a little bit late. But like the saying goes ‘better late than never’.

Whether women should perform breast self-examination (BSE) monthly or not has been a controversial topic. In 2003, the Cochrane Review published their analysis on the beneficial effect of screening by BSE and its impact on breast cancer death rate. The study, based on two large population-based studies conducted in Russia and Shanghai, concluded that BSE was not efficacious in reducing breast cancer death rate. The study suggested that BSE caused more harm since it identified a greater number of benign lesions and led to an increased number of biopsies being performed. Consequently several organizations have backed away from recommending self BSE while others have continued. The review was updated in 2008 and since no new studies were available since 2003, the review came to the same conclusion.

At the recent 10^th Annual Meeting of the American Society of Breast Surgeons, a study from Duke University found BSE to be accurate and efficacious in detecting breast cancer in high-risk women. The study involved 147 women at high risk of developing breast cancer. The women had mammography, MRI and BSE training at study entry. Thereafter, they performed BSE every 6 months and mammography and MRI screening every 12 months. At 3 year follow-up, the proportion of patients detected with breast cancer by BSE, mammography and MRI was about the same.

The controversy about whether BSE is useful or not will continue. One of the criticisms leveled at the Russian and Shanghai studies on BSE was the low compliance in the study population. BSE may cause false positives in a proportion of women but no test in medicine is free of false positive results. For example, mammography has a false positive rate of about 11%. False positive results will lead to further intervention, including surgery.

To be able to perform a proper BSE, one has to be taught. Some women will find it relatively easy to pick up the skills, but others might find it difficult or shudder at the thought of finding something wrong in the breasts. For the latter group of women, BSE is probably not going to work and they are better off going to their doctor for regular breast examination. For those who are adept at BSE, BSE could be viewed as a means of becoming more familiar with their bodies. It should not be viewed as a substitute to their visits to the doctor for the recommended screening programme; it should be seen as an adjunct.

The World Cancer Research Fund (WCRF) and its sister organization, the American Institute for Cancer Research (AICR) in their recent report titled ‘Policy and Action for Cancer Prevention’ stated that approximately one third of common adult cancers in the US may be preventable. (This is not including those which can be prevented by not smoking.) The WCRF and AICR estimated that eating a nutritious diet, being physically active and keeping body fat under control may prevent:

• 38% of breast cancers
• 45% of colorectal cancers
• 36% of lung cancers
• 39% of pancreatic cancers
• 47% of stomach cancers
• 69% of esophageal cancers
• 63% of cancers of the mouth, pharynx, or larynx
• 70% of endometrial cancers
• 24% of kidney cancers
• 21% of gallbladder cancers
• 15% of liver cancers
• 11% of prostate cancers

According to the report, diet, physical activity and limited body fat could prevent 34% of these 12 cancers overall and 24% of all cancers.

A study from the Karolinska Institute followed 45,920 Swedish male conscripts from the period 1969 - 70 for 38 years and examined the effects of overweight in adolescence on subsequent adult mortality (BMJ 2009; 338: b496). Compared with normal weight [body mass index (BMI) 18.5 – 24.9 kg/sq.m] men, the mortality risk in overweight (BMI 25 – 29.9) and obese (BMI ≥ 30) men was increased by 33% and 114%, respectively. The risk was not increased in underweight men, but in those who were extremely underweight, BMI < 17, the risk of mortality was increased by 33%. The risk of mortality in light (1 – 10 cigarettes / day) and heavy (> 10 / day) smokers was also increased by 54% and 111%, respectively, when compared to non-smokers. (Since the start of this study the number of overweight adolescent men in Sweden has tripled and the number of those who are obese has increased 5 fold. Fortunately, the number of smokers has halved.)

Another study looked at the effects of alcohol consumption on the incidence of cancer risk in 1,280,296 women involved in The Million Women Study (J Natl Cancer Inst 2009; 101: 296 – 305). They attended breast cancer screening clinics in the United Kingdom from 1996 to 2001. The average follow-up time was 7.2 years. The 5 categories of alcohol intake were 0 (24%), up to 2 (29%), 3 – 6 (23%), 7 to 14 (19%) and at least 15 (5%) drinks of 10 g of alcohol (= 1 unit) / week. Increasing alcohol intake was associated with an increased risk of specific cancers. The excess cancer incidence of these cancers, up to 75 years of age, with 10 g increase in daily alcohol intake were:

• Oral cavity and pharynx – 1 per 1000
• Oesophagus – 0.7 per 1000
• Larynx – 0.7 per 1000
• Rectum – 1 per 1000
• Liver – 0.7 per 1000
• Breast – 11 per 1000

To put it another way, the researchers estimated that the background incidence of cancers among women in developed countries was 118 cancers diagnosed per 1000 women up to the age of 75 years. Drinking 1 unit per day increased this by an extra 15 cancers per 1000 women and 2 drinks a day  increased this an extra 30 cancers per 1000 women; the majority of the cancers would be breast cancer.

Most cancers are not inherited. For the small proportion of inherited cancers, your cancer risk is not within your control. For most of us, how you lead your life can impact on your cancer risk. Leading a healthy lifestyle does not reduce your cancer risk to zero; it does however reduce your odds of developing cancer. Do not think that regular health checks will save you from cancers. You hope that the checks will help you detect the cancer at an earlier stage, and that is no guarantee either. A healthy lifestyle has no downside. Embracing it might just save your life!