|
| (A) The increase is apparent (not more cancers but more detection) | |
| (i) Widespread diffusion of advanced medical procedures (ultrasounds and fine needle aspiration biopsy) | |
| (ii) The increased incidence concerns mainly microcarcinomas | |
| (iii) Increased detection of “incidental,” microcarcinomas because | |
| (1) total thyroidectomies for benign lesions are more frequent | |
| (2) pathological examinations are more detailed | |
| (3) incidental discovery of nodules at diagnostic examination for other diseases is frequent | |
| (iv) High frequency of undiagnosed, asyntomatic small thyroid cancers at autopsy | |
| (v) Improved accuracy of cancer registration | |
| (B) The increase is true (more cancers because of changes in the risk factors) | |
| (i) Large tumors are also increased | |
| (ii) The incidence of large size and advanced stage cancers is not decreased, as expected when early diagnosis is more frequent | |
| (iii) Only the papillary histotype of thyroid cancer is increased | |
| (iv) Increased incidence is not proportionally distributed for age and gender (secular trend is greater for females and a birth cohort pattern is present) | |
| (v) Improved accuracy of cancer registration should have produced similar effects also for other tumors | |
| (vi) Mortality rate | |
| (1) stable mortality rate may result from early diagnosis and better treatment counteracting the effect of the increased cancer number | |
| (2) thyroid cancer progression is very slow and increased incidence would affect mortality only after decades | |
| (3) recent data indicate that mortality is increasing, specially in males | |
|
