Cancer and its prevention
The 3 main causes of cancer death in men are lung, bowel and prostate, respectively.
There are several forms of lung cancer and whereas only bronchogenic cancer is smoking related, this is the most common form.
Smoking causes so much increase in mortality from heart disease and cancer that there can be no other message than ‘please stop now!’
To prevent lung cancer – eliminate smoking
Colorectal cancer
What are the statistics?
The lifetime risk of colorectal cancer [CRC] is 5%. The third most common cancer in the UK with ~32,000 new cases annually.
The overall 5-year survival rate in England is approximately 50%, but this hides a picture of good survival in early disease and catastrophic survival chances in even moderately advanced cases. Once some tumour spread has occurred treatment becomes difficult and no new treatment options are on the horizon. Thus preventing this disease is critical.
Most CRC’s develop from adenomatous polyps on the lining of the intestine. Adenomas are asymptomatic and common: most do not develop into cancer. In fact, a third of the population develop at least one adenoma by age 60.
Premalignant change exists ~ 10 years before CRC develops so detection and prevention are possible.
Most bowel cancers arise from a polyp [adenoma] such as the one shown in the picture. The transition from benign adenoma through abnormal polyp to cancer may take 10 years. It can therefore be useful to both detect polyps before they become cancer and make lifestyle modification to prevent either polyp formation or polyp transformation. Not every polyp is potentially pre-malignant – about 30% of men get one by age 60 so clearly many remain just polyps.
Until we have a means of identifying the hazardous polyps it is necessary to look at issues such as screening and chemoprevention in the whole population to deal with the small number of polyps that are dangerous.
There is time to do something and there are clear guidelines about what to do.
The key facts that determine what we should do
- The biggest risks are age and family history.
- Lifestyle issues [diet, exercise, alcohol] make a substantial contribution.
- Most cancers arise from pre-cancerous conditions and take up to 10 years to progress to cancer.
- There is now a screening programme with proven success.
- Daily low dose aspirin is successfully preventative: other dietary modifications probably help.
| Age & Family history | Another risk factor – inflammatory bowel disease |
|
About 25% of colorectal cancers occur in individuals with a family history of the disease. A number of genes have been identified that increase CRC risk. In addition, because polyps are important precursors of CRC, two inherited conditions that cause multiple polyp formation contribute 5% of that number. These are Familial Adenomatous Polyposis [FAP] and hereditary non-polyposis colorectal cancer [HNPCC]. Anyone with a family history should start screening |
The risk of CRC is increased with a history of inflammatory bowel disease. Such individuals will already be under regular surveillance. |
Actions to prevent CRC
| Because… | Do this… |
| Bleeding may indicate polyps or cancer | Consult GP urgently if any rectal bleeding |
| Obesity increases risk substantially | Get to ideal weight [waist circumference 90cm or less] |
| Vitamin D deficiency increases risk | Take a supplement [800iu daily] |
| Screening is available over age 60 | Participate when invited, enquire if not invited |
| Aspirin reduces polyp risk by 20% and colon cancer risk by 26% in the short term. After 5 years use daily aspirin reduces incidence and mortality due to colorectal cancer by 30-40 % after 20 years of follow-up | Take 75mg gastro resistant aspirin daily |
| CRC is partly caused by inflammation. There is evidence to support the value of Omega 3 PUFA’s in prevention |
Take Omega 3 [2G daily ] |
| CRC depends on the balance of ‘good’ and ‘bad’ bacteria in the colon. | Add prebiotic [live yogurt, lactobacilli culture] and probiotic [inulin, pectin, lactulose or similar] into diet. |
Note: Risks of aspirin. As more data has become available showing the benefit of cancer in reducing the prevalence of several cancers [in a pooled analysis of individual patient data from 8 randomized controlled trials of aspirin versus control, daily aspirin for 5–10 years, reduced in-trial cancer deaths after 5 years by 34% :p = 0.003, with a 10% reduction in all-cause mortality during the trials, and reduced the 20-year risk of cancer death by 20% p=0.0001] and the low risks with the 75mg dose of aspirin [1-2 stomach bleeds per 1000 with no serious consequences and only 1-2/10,000 intracranial bleeds] the risk benefit analysis comes up with a reduction in all cause mortality ie many fewer deaths prevented by aspirin than caused by it.
Screening
Currently FOB [faecal occult blood] screening is offered to over 60’s in the UK. A small stool sample is tested for signs of blood.
In the USA colonoscopy is popular [but invasive and expensive]
For those at high risk ‘virtual’ CT colonoscopy has been developed. This uses new CT scanning techniques to obtain 3D pictures of the inside of the bowel. It is currently thought too expensive to be offered to all in the UK but will be useful for high-risk individuals and surveillance. However Pickhardt writing an American perpesctive in Lancet Oncology states:
The bottom line is quite simple:
Too many people are dying of a readily preventable disease. The issue with screening for colorectal cancer is not related to test efficacy per se, but rather to the willingness of patient participation (and study availability). By offering the additional option of CT colonography for screening, overall patient outcomes will be positively affected by the equivalent (or greater) yield for advanced neoplasia coupled with a decrease in complications and costs. Of note, both colonoscopy and CT colonography confer the crucial advantage of cancer prevention through detection (and removal) of advanced adenomas over the cancer detection aspect alone that is provided by current stool-based testing. The additive yields of having both colonoscopy and CT colonography available as primary screening options could have a profound effect on the incidence and mortality of colorectal cancer in the future.
Prostate cancer
Prostate cancer is the most common cancer in men in the UK. Over 40,000 men are diagnosed with prostate cancer every year. 250,000 men are currently living with the disease.
Prostate cancer can grow slowly or very quickly. Most prostate cancer is slow-growing to start with and may never cause any problems or symptoms in a man’s lifetime. However, some men will have cancer that is more aggressive or ‘high risk.’ This needs treatment to help prevent or delay it spreading outside the prostate gland.
Treatment controversies
There are some difficulties underlying our current medical approach to treating prostate cancer in other words some unanswered questions around the best treatment for the early compared with aggressive forms. The latest evidence is that localised disease should be treated less, possibly just monitored and that aggressive cancer needs more aggressive treatment probably involving improved radiotherapy options as part of the schedule.
Screening – there is no screening programme in the UK
In terms of preventing prostate cancer the situation is equally controversial. In the USA, screening with PSA [prostate specific antigen] has been widespread. Recent review by a US government task force confirm that it is a very poor screening test as currently used.
For a full review of screening see Cancer Research UK’s website.
Trials are underway in London testing a combination of PSA with high detail MRI scanning. The method being tested is PICTURE – Prostate Imaging (Multi-parametric MRI and Prostate HistoScanning™) Compared to Transperineal Ultrasound Guided Biopsy for Significant Prostate Cancer Risk Evaluation.
This answers all of the criticisms of previous screening strategies and is likely to be the way forward. See here if you want to enrol.
Vitamins & minerals
Some studies have suggested that certain vitamin and mineral supplements (such as vitamin E and selenium) might lower prostate cancer risk. But a large study of this issue, called the Selenium and Vitamin E Cancer Prevention Trial (SELECT), found that neither vitamin E nor selenium supplements lowered prostate cancer risk after daily use for about 5 years. In fact, men taking the vitamin E supplements were later found to have a slightly higher risk of prostate cancer.
Another vitamin that may be important is vitamin D. Recent studies have found that men with high levels of vitamin D seem to have a lower risk of developing the more lethal forms of prostate cancer.
