BACKGROUND: The incidence of most cancers increases with age from early adulthood into old age but tends to level off or decrease at the highest ages. This decline may be caused by age-related mechanisms or due to lower diagnostic activity, leaving some cancers undiagnosed at the oldest ages.
METHODS: For breast, colon, lung, and all sites except non-melanoma skin cancer, age-specific incidence rates of verified as well as suspected cancer were estimated up to ages 95+ years for a random sample of the Danish population, 1994-2011, based on nationwide health registers (40,008 verified and 9110 suspected cancers). Moreover, for cancers diagnosed in Denmark, 1978-2012 (613,384 cancers), age-specific percentages of tumors with microscopic verification (histological/cytological/hematological examination) were calculated.
RESULTS: The age-specific cancer incidence rates reached a peak between ages 65-89 years after which rates declined. The corresponding incidence pattern of suspected but not verified cancer was similar, with a trend of a slight absolute and relative decrease with age compared to verified cancer incidence. The proportion of cancers with microscopic verification decreased linearly from approximately 95% at ages 0-69 years all years to 70% (1978-1982) and to 80% (2010-2012) at ages 90+ years.
CONCLUSIONS: The lower diagnostic verification of cancer at the highest ages suggests a lower diagnostic activity among the oldest-old. However, the proportion of suspected but not verified cancers did not increase with age, possibly partially due to lack of registration. The declining cancer incidence at oldest ages is probably partly due to lower diagnostic activity.