Page 39 - 20dynamics of cancer

24 CHAPTER 2

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Figure 2.4 Age-specific incidence of childhood cancers on log-log scales. Inci-
dence is given as log 10 of the number of cases per one million population per
year. Data from Ries et al. (1999) for both sexes and all races from the USA. Cir-
cles show the actual data; lines show curves fit by the smooth.spline function
of R with a smoothing parameter of 0.4 (R Development Core Team 2004).

cessation of growth. Carcinomas mostly increase in incidence through-
out life, because the epithelial cells continue to divide and renew those
tissues at all ages.
The acceleration patterns for these cancers provide an interesting
view of changes in incidence with age (Figure 2.5). The inherited syn-
dromes have accelerations near zero or below, with a tendency to decline
with age. Teen onset testicular cancer and osteosarcoma have declining