Background The incidence of thyroid cancer has increased over the last few decades in many countries, particularly in developed countries and markedly in the Australian state of New South Wales (NSW). To investigate whether these changes may be due to increased detection we studied the clinical pathways leading to the diagnosis of thyroid cancer.
Methods Newly diagnosed cases of thyroid cancer were identified and recruited through the population-based NSW Central Cancer Registry. Participants completed a questionnaire and diary of doctor visits and investigations that led to their diagnosis. Tumour characteristics were obtained from pathology reports.
Results 452 people (76% female) with thyroid cancer completed the study. The median age at diagnosis was 48 years for women and 53 for men. Only 40% of diagnoses occurred after the patient reported a lump or symptom and 60% of diagnoses were serendipitous. The pathways to diagnosis varied significantly with tumour size (p=0.001) and by age in men (p=0.008) and place of residence in women (p=0.05). Not all of the increase in incidence is explained by increased detection. Allowing for cases diagnosed serendipitously, the estimated age-standardised incidence rates for men (3.83 per 100 000) and women (10.65 per 100 000) were well below those observed (4.65 and 15.3 respectively).
Conclusion As the diagnosis of only 40% of thyroid cancers was patient initiated, the reported incidence of thyroid cancer is likely to be influenced by diagnostic technology and medical surveillance practices. This, however, probably only partly explains the observed rise in incidence of thyroid cancer in NSW.
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