| Japanese Journal of Clinical Oncology | Pages |
Letter
The Probability of a Japanese Person Developing Cancer During Their Lifetime
In the recent vital statistics of Japan (1996), it was reported that cancer deaths accounted for 33.7% in males, 26.1% in females and 30.3% in both genders in all causes of death (1). In these figures, percentages of patients with a cured cancer who died from other causes were not included. The probability of suffering from cancer in the whole lifespan of a Japanese person including cured cancer cases could be estimated based on data of a population-based cancer registry by using two simple methods. One is to multiply the percentage of cancer deaths from all causes by the incidence/death (I/D) ratio (2). In this way, it was estimated that the proportion of persons developing cancer in the whole lifespan of a Japanese person was 57.6% in males, 49.3% in females and 53.9% in both genders. Another method is to calculate the cumulative risk of cancer from the cumulative incidence rate of cancer up to a certain age based on the age-specific incidence rate for all sites of cancer (3). By using this method, the cumulative risk of cancer for all sites has been calculated for each cancer registry (4). However, in a series of monographs (3,4) entitled Cancer Incidence in Five Continents only cumulative risks for 0-64 and 0-74 years old, which are much shorter than the average life expectancy in Japan today, were calculated. Therefore, I tried to calculate the cumulative rates and cumulative risks of cancer in Japan for age up to 85+ years in both genders and up to 77 years for males and 84 years for females, which correspond to the current average life expectancy in Japan. For ease of calculation, the 85+ age category was assumed to be 85-89 years. The cumulative rate (100x) was converted into cumulative risk by using the formula 100(1 - e-x) (3). In this method, the cumulative rate of developing a cancer up to 85+ (up to 89) years old was 72.9% in males, 36.9% in females with an average of 54.9% for both genders. The corresponding cumulative risk was 51.8% in males and 30.9% in females with an average of 41.4% for both genders. The cumulative percentage of developing cancer up to the average life expectancy of the Japanese (77 years old in males and 84 years old in females in 1998) was 35.6% in males and 34.0% in females with an average of 34.8% for both genders. The corresponding cumulative risk was 30.0% in males and 28.8% in females with an average of 29.4% for both genders. If a person survives longer than the average life expectancy, the cumulative risk of developing a cancer will become larger with further increase in age and approach the maximum percentages for 85+ (up to 89) years.
In calculating the cumulative rate and cumulative risk of cancer based on age-specific cancer incidence rates, the competing risk with other causes of deaths was not considered in the present calculation (3). However, it may be reasonable to claim that at least three out of 10 persons die of a cancer in their whole lifespan in Japan. It may also be possible that as many as five out of 10 persons suffer from a cancer in their whole lifespan if he/she survives long enough; much longer than the average life expectancy in Japan. If he/she survives to the age corresponding to the average life expectancy in Japan today (77 years for males and 84 years for females), it is likely that three out of 10 persons will suffer from a cancer before their death.
- Vital Statistics of Japan 1996. Statistics and Information Department, Ministry of Secretariat, Ministry of Health and Welfare 1998 (in Japanese).
- Research Group for Population-based Cancer Registration in Japan. Cancer incidence and incidence rates in Japan in 1994: estimates based on data from seven population-based cancer registries. Jpn J Clin Oncol 1999;29:361-4.
- Day NE. Cumulative rate and cumulative risk. In: Parkin DM, Muir CS, Whelan SL, Gao YT, Ferlay J, Powell J, editors. Cancer Incidence in Five Continents, vol. VI. Lyon: International Agency for Research on Cancer 1992;862-4.
- Parkin DM, Whelan SL, Ferlay J, Raymond L, Young J, editors. Cancer Incidence in Five Continents, vol. VII. Lyon: International Agency for Research on Cancer 1997;1062-3.
Suketami Tominaga
Aichi Cancer Center Research Institute, Nagoya, Japan
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