Sunday, 2 November 2008

Prostate Cancer

Last night I went for a curry with John H who I've known for fifty years. At 82, he was diagnosed with Prostate Cancer earlier this year. Treatment is with 'hormonal injections' to control his PSA levels. He's had a negative test in a body scanner for bone cancer.

John H mentioned that high PSA (Prostrate Specific Antigen) (wikipedia) levels can be an indicator of Prostate Cancer. "All men over 50 in USA know about these figures" said John. A month ago we heard that our good friend Jonathan Fs' father, in his mid 70s, has prostate cancer.

  • source: CancerResearchUK
  • Prostate cancer is the most common cancer in men in the UK. A quarter of all new cases of cancer diagnosed in men are prostate cancers.
  • In 2005, more than 34,000 men in the UK were diagnosed with prostate cancer.
  • Over the last 30 years prostate cancer rates in Great Britain have almost tripled, although much of the increase is due to increased detection through widespread use of the PSA test.
  • Almost 60% of prostate cancer cases are diagnosed in men aged over 70 years.
  • Around 7 in 10 newly diagnosed prostate cancer patients now survive beyond five years. In the 1970s it was only 3 in 10.
  • Prostate cancer is the second most common cause of cancer death in UK men, after lung cancer.
  • Each year around 10,000 men in the UK die from prostate cancer
  • The majority of prostate cancer deaths (93%) occur in men aged 65 and over as Figure 2.1 shows (source)

PSA is, like Trypsin, a serine protease.

The U.S. Food and Drug Administration (FDA) (wikipedia) has approved the PSA test for annual screening of prostate cancer in men of age 50 and older. PSA levels between 4 and 10 ng/mL (nanograms per milliliter) are considered to be suspicious and should be followed by rectal ultrasound imaging and, if indicated, prostate biopsy. PSA is false positive-prone (7 out of 10 men in this category will still not have prostate cancer) and false negative-prone (2.5 out of 10 men with prostate cancer have no elevation in PSA).[19]

Diet has been extensively researched because of the large variation in prostate cancer incidence between different cultures and their traditional diets around the world, particularly the Asian versus ‘western’ diet. A variety of factors have been looked at but much of the research is at present inconclusive. A recent review of the evidence concluded that foods containing lycopenes and selenium probably have a protective effect while diets high in calcium may increase risk.16 (source: CancerStats)
Lycopene, found principally in tomatoes and tomato-based products, may reduce the risk of prostate cancer. Cooked and processed tomatoes, such as tomato sauce, are a better source of lycopene than fresh tomatoes. A meta-analysis of 21 studies published from 1966–2003, showed that men with the highest intake of cooked tomato products had a 20% reduced risk of prostate cancer compared to men with the lowest intake.17 (source: CancerStats)
Since then, three studies including the European Investigation into Cancer and Nutrition (EPIC) study18-20 have shown a significant protective effect with higher intake of lycopene, although three other studies showed no association.21-23 (source: CancerStats)
Several studies have shown a protective association for selenium, reporting a 30–80% risk reduction for prostate cancer.24-26 However, at least three studies showed no association.27-29 Further research is needed and the Selenium and Vitamin E Cancer Prevention Trial (SELECT) may provide much needed answers.30 (source: CancerStats)

Calcium and dairy products

Some cohort studies have shown a raised risk of prostate cancer for men with high intakes of calcium from diet and/or supplementation31-34 but others have not.35-37
Dairy products, as a source of calcium, have been extensively studied in relation to prostate cancer. Several cohort studies show a small significant increase in risk but findings differ by whether it affects advanced or localised tumours.34-39
The EPIC study showed overall a 32% increased risk for 35g/day higher intake of dairy protein and a 7% risk increase for an 0.3g/day intake of dairy calcium. Protein and calcium from non-dairy sources were not associated with risk.40
An easy guide to cancer statistics is here and here.

Evidence suggests that around half of all cases of cancer diagnosed in the UK could be avoided if people made changes to their lifestyle. (source)

Bodyweight and risk of cancer in the UK

There is convincing evidence that being overweight or obese increases cancer risk1. Estimates suggest that, in the UK, more than 13,000 cases of cancer (about 4% of all cases) could be avoided if no-one exceeded a body mass index (BMI) of 252. Table 2.1 summarises what we currently know about overweight, obesity and risk of cancer.

Physical activity and risk of cancer

More than 60 studies have looked at the association between physical activity and colon cancer, the overwhelming majority showing a reduced risk with higher levels of exercise. The largest cohort studies suggest that the risk reduction for the most active people is between 20% and 25%.1,2
Physical activity may affect colon cancer risk in various ways, including by reducing faecal transit time, inflammation and insulin resistance

and modifying hormone metabolism.3,4

Diet, alcohol and cancer in the UK

Alcohol and cancer risk

Alcohol is well established as a cause of cancer: Around 6% of UK cancer deaths could be avoided if people did not drink.1
Alcohol consumption increases the risk of oral (oral cancer includes cancers of the oral cavity, pharynx excluding nasopharynx and lip), laryngeal, oesophageal, breast, bowel and liver cancer. Risk of cancers of the upper aerodigestive tract (oesophagus, oral cavity, pharynx and larynx) increases linearly with quantity of alcohol consumed above 25g/day . Someone drinking 100 g/day has a 4–6-fold increased risk of these cancers compared to light or non-drinkers.2

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