Authors
Ganmaa et al

Title
Incidence and mortality of testicular and prostatic cancers in relation to world dietary practices

Journal
International Journal of Cancer 98:262-267 (2002)

Summary
The incidence of both testicular cancer and prostate cancer in western countries has increased over the last 50 years. Although testicular cancer represents only 1 percent of all cancers in men, it is the most common form of cancer in young men between the ages of 15 and 35. Prostate cancer is the most commonly diagnosed cancer in men in Europe, North America, and Australia with more than 75% of cases diagnosed in men over the age of 65. Recent scientific evidence clearly indicates that diet has an important influence on testicular and prostate cancer risk. Dietary factors may also influence the rate at which a small tumor changes from a small growth causing no clinical symptoms into a more aggressive, spreading tumor.

The authors of the present investigation sought to correlate the incidence and mortality of testicular and prostatic cancers in 42 countries with dietary practices in these countries. Cancer incidence rates between 1988 and 1992 were obtained from the International Agency for Research on Cancer (IARC) and age-specific mortality rates of both cancers were provided by GLOBOCAN 1. Food consumption data (Mt/1,000 capita/year) from 1961 to 1991 was provided by the Food and Agriculture Organization (FAOSTAT Database Collections) and converted into g/capita/day.

Switzerland had the highest incidence rate of testicular cancer in the 29 to 39 age group (22.2/100,000), followed by Denmark (21.8) and Germany (20.2). Algeria and Zimbabwe had the lowest rate (0/100,000), followed by Uganda (0.32) and Mali and China (both 0.49). Cheese was found to be most closely correlated with the incidence of testicular cancer (r = 0.80). In addition, stepwise-multiple-regression analysis indicated that milk + cheese consumed between 1961 and 1965 contributed the most to the incidence of testicular cancer around 1990 (R = 0.654). These results suggest that maternal and/or prepubertal consumption of cheese and/or milk may be a risk factor in the development of this cancer.
The correlation coefficient between the incidence and mortality of testicular cancer was low at 0.35. Early detection and a combination of surgery, chemotherapy, and radiation have greatly increased the survival rate of patients with this disease. In fact, testicular cancer has one of the highest cure rates of all cancers. Therefore, incidence is a better index for this disease than mortality.

The incidence rate of prostatic cancer was highest in the U.S. (101/100,000), followed by Canada (65), Iceland (61) and Sweden (55). Korea had the lowest incidence rate (0.9), followed by Vietnam (1.2), Algeria (1.8) and China (1.9). Milk consumed between 1961 and 1990 was found to be most closely correlated with prostatic cancer incidence (r = 0.71) and mortality (r = 0.77). In addition, stepwise-multiple-regression analysis indicated that milk + cheese consumed between 1961 and 1990 contributed to an increased incidence (R = 0.52) and mortality (R = 0.58) of this malignancy. The correlation between the incidence and mortality rates of prostatic cancer was high (r = 0.8).

Milk and other dairy products are the leading source of exogenous estrogen in developed countries. Estrogens have been shown to be associated with the development and growth of prostatic cancer. Endogenous estrogens are quickly removed from the bloodstream by the liver, but exogenous estrogens can remain in the blood for a longer time and thus cause damage. In addition, it is not unreasonable to assume that hormones in dairy products may also be associated with the development of testicular cancer. In most countries, the risk of developing testicular cancer in boys aged 15-19 years is much greater than in boys aged 5-14 years. This suggests that the presence of sex hormones and/or gonadotropins that develop after the onset of puberty may be important risk factors in the development and growth of this cancer.