Randomised trials specifically designed to investigate this aspect are not available, but all process indicators (positive predictive value, length of sojourn time, sensitivity of the test) indicate that screening efficacy does not change with increasing age.
Firstly, varying the distribution of sojourn time yielded mean estimates of the proportion of overdiagnosis that ranged from 0.0%to3.9%9% for invasive cancer and from 12.4% to 51.7% for carcinomas in situ (table 2).
To illustrate the influence of Weibull parameters of sojourn time distribution (STD), we vary the shape parameter b from 0.5 to 5 and change the scale parameter a to make sure the expectation of sojourn time is 10.
This can cause underestimation of sojourn time and overestimation of sensitivity.
The first of these must undoubtedly happen, but given the low all-cause mortality rates of women in the age groups invited for screening, and the likely mean and distribution of sojourn time, this type of overdiagnosis is liable to be very rare [ 4].
The landmark meta-analysis from the International Agency for Research on Cancer (IARC) provided no details regarding the age dependence of the results, but stated that "age did not affect either the sensitivity of cytological screening or the distribution of the sojourn time of the disease.
Then, using a probabilistic model that takes into account background incidence, competing risks, distribution of sojourn time in preclinical state, sensitivity of mammography and the dissemination of screening in Catalonia, we estimated the increased age-specific incidence due to lead time (expected incidence).
Our results suggest that overdiagnosis increases with age, partly due to our assumption of a homogeneous model of sojourn time within each age group, and to the fact that the observed prevalence to incidence ratio was similar in all age groups.
Breast cancer is a heterogeneous disease, with grades of metastatic potential and length of sojourn time [ 51].
Detection rates are affected by the duration of sojourn time and by the proportion of lesions that regress.
