The tumour–patient classification of cancer overdiagnosis2
| Cancer overdiagnosis occurs because screening detects … | Indolent or non-indolent cancer? | Example of a screening programme likely to produce overdiagnosis via this route | |
|---|---|---|---|
| Tumour A | “Asymptomatic malignant disease that regresses spontaneously if left alone” | Indolent | Neuroblastoma screening of infants |
| Tumour B | “Asymptomatic malignant disease that either stagnates or progresses too slowly to be life threatening in even the longest of lifetimes” | Indolent | PSA testing to detect prostate cancer risk |
| Patient | “Asymptomatic malignant disease that progresses quickly enough to be life threatening during a lifetime of typical length, but death because of another cause occurs prior to what would have been the destined date of symptomatic diagnosis had screening not occurred” | Non-indolent | Low-dose CT scanning for lung cancer (because heavy smokers may die of another smoking-caused disease before they die of lung cancer) |
To quote Marcus et al: “We believe that the ratio of tumour to patient-driven overdiagnosis almost certainly varies by organ, screening modality, patient characteristics, and other factors” (p. 2).
PSA, prostate specific antigen.