ABSTRACT
Background The linear association between median age at cancer onset and median age of the underlying population has been described only for breast cancer. We quantified the shape and strength of such association for 20 cancer types using data from all population-based cancer registries (CRs) worldwide. Methods The patients' median age at cancer onset and of the underlying population were extracted from all CRs listed in volumes VI (1983-1987 years) and XI (2008-2012 years) of Cancer Incidence in Five Continents. The association was assessed at cross-sectional level by linear regression models and longitudinally considering only the long-standing CRs active throughout the study period (i.e., 25-year span). Results During 2008-2012, each one-year increase in median population ageing was associated in men with a nearly half year increase of median age at onset of all cancers, but skin; and a 2/3 year increase in women. Variance explained by linear model was around 60%. In long-standing CRs a decrease in median age at cancer onset was observed for prostate and cervical cancers throughout the 25-year span. Conclusions Population ageing reflected 60% of the median age at cancer onset. Misinterpretation of peaks of cancer incidence in specific age groups may be avoided by examining population pyramids.
ABSTRACT
BACKGROUND: Incidence rates of thyroid cancer (TC) increased in the last decades worldwide. This study aimed to describe TC incidence in the Friuli Venezia Giulia (FVG) region, to estimate the quota of overdiagnosis, and to investigate the impact of surgery on long-term survival after TC diagnosis. METHODS: TC cases reported to the FVG population-based cancer registry during 2002-2013, aged <85 years, were included. Age standardized rates (ASR) on the European population were computed, while proportion of TC overdiagnosis was estimated in comparison with expected age-specific incidence rates from published time series. Adjusted hazard ratios of death, with 95% confidence intervals, were also estimated. RESULTS: During 2002-2013, 1701 TC cases were reported to the FVG cancer registry, with papillary TC (78.2%) as the most frequent histologic type. ASR increased from 12.4 to 16.5 in women and from 4.3 to 6.2 in men (+33.1% and +44.2%, respectively). Overdiagnosis was estimated as 79% of TC cases in women and 64% in men. Almost all TC cases (97.1%) underwent surgery, including 84.6% of women and 78.9% of men who underwent total thyroidectomy. Up to 10 years after TC diagnosis, the type of surgery did not appear to influence survival. CONCLUSIONS: This study documented an increase in TC incidence in FVG in the last decade, with overdiagnosis accounting for a large proportion of TC diagnoses and total thyroidectomy in more than 80% of cases. These findings suggest reconsidering thyroid screening practice and aggressive therapeutic strategies, as recommended by new TC guidelines.
