Public discussions about time trends in the burden of cancer are full of debates about apples and oranges. Some people focus on changes in the incidence of cancer--the proportion of people struck by cancer-- while others focus on cancer mortality, the rate at which deaths are caused by cancer. These are very different measurements.

There are legitimate reasons to focus on cancer mortality, especially to evaluate the efficacy of cancer treatments. Cancer mortality rates are vital. If you want to learn, however, about the causes of cancer and use that to guide cancer prevention, it is the wrong thing on which to focus. This is because cancer treatment has improved enormously over the past several decades and thus people survive much longer now after contracting many types of cancer. The rates at which people contract cancer can be increasing even as cancer mortality rates can be going down.

Dinse, GE, DM Umbach, AJ Sasco, DG Hoel and DL Davis. 1999. Unexplained increases in cancer incidence in the United States from 1975 to 1994. Annual Review of Public Health 20: 173-209.

Dinse et al. examine US data from 1975 to 1994 focusing on long-term time trends in the incidence of various cancers. They use a sophisticated statistical analysis to tease apart the effects of age, period and birth cohort. They find that while several important cancers are decreasing in frequency, especially lung cancer, others are increasing.

• Overall cancer rates have increased by 22% and 56% among white women and white men, repectively, over the course of a single generation. Increases in black men and women are comparable.
• "A contemporary woman's risk of breast cancer is 54% greater than was her mother's at the same age among blacks and 41% greater among whites."
• "Men today have about a three- to four-fold risk of being diagnosed with prostate cancer compared with their fathers."
• Excluding cancers linked to smoking, or where trends are confounded by changes in diagnostic procedure (breast and prostate; see below), "relative to the previous generation, rates increased on average 13% in black women, 52% in white men, and 67% in black men." There was little change in white women.
• For non-Hodgkin's lymphoma, which they analyzed separately, the rates today relative to 25 years ago have "almost doubled in white women, nearly tripled in black women, more than tripled in white men, and more than quadrupled in black men."

Møller, H. 1998. Trends in sex-ratio, testicular cancer and male reproductive hazards: Are they connected? APMIS 106:232-239.

As several other authors, Møller reports very significant increases in testicular cancer among men in northern Europe, more than doubling in several countries since 1960. His analysis suggests it is linked to a syndrome of disorders in the male reproductive tract, resulting from developmental disturbances in the womb. More...

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