16 The burden of cancer overdiagnosis in Australia

Abstract

Burden of cancer is increasing worldwide, and in Australia, partly due to overdiagnosis: cancers which would never cause symptoms or harm if left undetected. We sought to estimate the current burden of overdiagnosis of cancer in Australia.

We calculated and compared current (2012) and past (1982) lifetime risks of cancer for 5 cancers: prostate, breast, renal, thyroid cancers and melanoma. Using routinely collected Australia-wide data on cancer specific incidence and mortality, we used the Devcan software to estimate the probability of cancer specific diagnosis for each age group adjusted for the competing risk of dying from other causes. To account for increases in breast cancer and melanoma from changes in risk factors over time, we adjusted the lifetime risk of these cancers in 1982 upwards. To estimate the overall overdiagnosis we multiplied each cancer’s estimated overdiagnosis by its incidence and summed these. For breast cancers and melanoma, we did sensitivity analyses excluding in-situ cancers.