Advances in diagnostic practices affect thyroid cancer incidence in France.
OBJECTIVE
To analyse trends in diagnostic practices of thyroid diseases and to relate them to the increase in thyroid cancer incidence in France over time.


METHODS
From 1980 to 2000, a French retrospective multicentric (three endocrinology and three nuclear medicine centres) study of thyroid diseases was conducted on 20 consecutive unselected patients' records, sampled every 5 years in each centre.


METHODS
Characteristics of the population and diagnosis procedures (thyroid ultrasonography (US), radionuclide scan, cytology and hormonal measurements) were described over time. Changing trends in operated patients and in cancer prevalence were analysed as well as the impact of practices on cancer incidence.


RESULTS
The study included 471 patients (82% female, mean age 46.7, range 9-84 years), referred for nodular thyroid diseases (66.7%) or thyroid dysfunctions (33.3%). A significant increase in US (3 to 84.8%) and cytological practices (4.5 to 23%), and a decrease (89.4 to 49.6%) in radionuclide scan procedures were observed over time. Although the proportion of patients undergoing surgery remained constant (24.8%), the prevalence of cancer increased among operated patients from 12.5 to 37% (P=0.006). In a Cox's proportional hazard model stratified on the clinical characteristics of patients, only the cytological practice, regardless of its results, was significantly associated with the occurrence of cancer: relative risk (RR)=4.4 (95% confidence interval (CI): 1.1-16; P=0.04).


CONCLUSIONS
From 1980 to 2000, a major evolution in clinical practices has led to the increase in thyroid cancer reported in France. Such changes in medical, as well as in surgical and pathological, practices must be taken into account in incidence measurement.
Leenhardt
L
L
Institut National de Veille Sanitaire, Saint Maurice, France. laurence.leenhardt@psl.ap-hop-paris.fr
Bernier
M O
MO
Boin-Pineau
M H
MH
Conte Devolx
B
B
Maréchaud
R
R
Niccoli-Sire
P
P
Nocaudie
M
M
Orgiazzi
J
J
Schlumberger
M
M
Wémeau
J L
JL
Chérie-Challine
L
L
De Vathaire
F
F
D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D005260:Female; D005602:France / Q000453:epidemiology; D006801:Humans; D006980:Hyperthyroidism / Q000175:diagnosis / Q000453:epidemiology / Q000601:surgery; D007037:Hypothyroidism / Q000175:diagnosis / Q000453:epidemiology / Q000601:surgery; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011159:Population Surveillance; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D013959:Thyroid Diseases / Q000175:diagnosis / Q000453:epidemiology / Q000601:surgery; D013964:Thyroid Neoplasms / Q000175:diagnosis* / Q000453:epidemiology* / Q000601:surgery; D016606:Thyroid Nodule / Q000175:diagnosis / Q000453:epidemiology / Q000601:surgery