Extending life: disease pattern shift

2. Malignant tumours and ageing

Tumour frequency increases with age (Fig. 3). The apparent decrease of frequency in the extreme ages of life is explained with a more difficult clinical diagnosis in the elderly. However, there is a real decrease in frequency after 90 years of age6.
There are also differences among tumours of different anatomical localization, and the median age presents an evident shift of even a couple of decades (fig. 4). The general median age in the Trieste population is around 71 years for the malignant tumours at all sites combined in males and females. But if we look at the tumours of different anatomical sites it is possible to note that the median age for skin melanoma in males is 61 years and 76 for prostate gland tumours with15 years of shift. In females the median age pattern change is even more evident: for cervix uteri tumours and skin melanomas the median age is 59 years, while for pancreatic tumours it is 78 — a difference of almost 20 years5. So we have three different groups of malignant tumours: those with a relatively young median age, that show a relative decrease with the ageing of the population; those that are around the general median age of malignant tumours for which no frequency changes are expected; and those characteristic of older persons, like gastrointestinal tumours that are expected to increase with the population ageing process.

Fig. 3: Increasing malignant tumours incidence in males and females by ageing
Fig. 4: Median age for different tumour anatomic location in males and females (general median age for all the malignant tumours together underlined)

Malignant tumours prevalence decreases in the later ages of human life. In people that die between 75 and 90 years of age, the tumour prevalence is around 36%6. The expected frequency is that one third of the population is going to develop a malignant tumour. Some years ago the common belief was that if everyone lives enough time they incur a malignant tumour. But the prevalence of cancer decreases to 22% in nonagenarians and to only 16% in centenarians (Table 2). This frequency decrease is also linked with less aggressive biological behaviour. In people under 90 years of age, cancer was the cause of death in 70% of cases, whereas in nonagenarians and centenarians cancer was involved with death in only 43% of of the cases. In most of these cases the metastatic spreading was not the final cause of death, but other local complications of the tumour such as infections or massive hemorrhages. The metastatic spreading was present in 2/3 of the elderly below 90 years, but only in 1/3 of the nonagenarians and in less than 1/4 of the centenarians6. Cancer in the oldest old could be considered in a different way from cancer in younger people. Often it is not the main disease influence the patients very greatly, but it is only one of the many chronic degenerative diseases that affect any person of this age, and, frequently, it is not even the most important one6.

Tab. 2: Malignant tumors prevalence, cause of death and metastatic spreading in elderly
From G. Stanta et al, Cancer of the oldest old, what we have learned from autopsy studies, Clin. Ger. Med.13:55-68; 1997

If we analyze time trends in cancer incidence, it is possible to note that the prevalence of tumours in people between 75 and 90 years of age was, in the years before the population ageing process (1940 – 1960), lower than nowadays: 11% versus 38%. This is probably the effect of environmental factors but also the effect of greater population ageing6.

Tab.3: Lung Cancer attributable risk by age
From: F. Barbone, M. Bovenzi, F. Cavallieri, G. Stanta, Air pollution and lung cancer in Trieste, Italy. Am J. Epidiemol., 141,1-9, 1995

The importance of environmental factors in the development of malignant tumours can be higher in the elderly than in young people. It was shown that, in the case of lung cancer, environmental pollution can be important in 28% of the cancers in persons under 70 years of age but in 46% of those over 70 (table 3)7. This can be explained by the fact that aged persons were already subjected to many hits in the multistep process of cancerigenesis and one more could be the one leading to the clinical disease.

6 G. Stanta, L. Campagner, F. Cavallieri, L. Giarelli, “Cancer of the oldest old: What we have learned from autopsy studies”, Clin. Ger. Med., 13:55-68 (1997).
7 F. Barbone, M. Bovenzi, F. Cavallieri, G. Stanta, “Air pollution and lung cancer in Trieste, Italy”, Am. J. Epidemiol., 141:1-9 (1995).

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