Major developments in the way thyroid cancer is detected and diagnosed have led to a massive increase in the number of people known to have the disease, according to a new study.

The report, published in the Canadian Medical Association Journal, says thyroid cancer diagnosis has more than doubled in the past decade, with an increase of 13 per cent per year, and 146 per cent over the 12-year study period.

Researchers used the Ontario Cancer Registry to identify 7,422 cases of thyroid cancer between 1990 and 2001 -- revealing the jump in the incidence rate of thyroid cancer.

A Canada-wide study (excluding Quebec) from 1970 to 1996 using the Canadian Cancer Registry also found an upward trend, with the age-adjusted incidence rate of thyroid cancer in females doubling from 3.3 per 100,000 at the beginning to 6.6 per 100,000 at the end of the study period.

In males, it went from 1.1 per 100,000 to 2.2 per 100,000, over the same period.

The trend is supported by numerous worldwide studies, the report says.

"One explanation is that we may be witnessing a true increase in the incidence of thyroid cancer, which has been termed 'an epidemic of micro-papillary thyroid cancers,'" the report states.

"A second is that the rising number of cases is apparent only because of changes in medical practices, particularly the increased use of ultrasonography and fine-needle aspiration biopsies."

It's also possible that a combination of both factors is contributing to the increased rates, the study suggests.

Dr. Jacques How, head of the division of endocrinology at Montreal General Hospital who wrote a commentary accompanying the research, believes better detection methods are behind the spike.

"The major reason for the rise is that it is being detected in greater numbers through changes in medical practice, by which I mean the availability of imaging of head and neck and with increasing use of fine-needle aspiration biopsies of any lumps or nodules that are detected by aforementioned detection processes," How told CTV.

The new methods are allowing doctors to detect the presence of smaller cancers in the thyroid gland. Nearly 50 per cent of the cancers being diagnosed now are less than one centimetre in diameter, "which is really, really small."

"Very often they are picked up incidentally during some sort of imaging for a non-thyroid reason."

Though there is consensus to support the conclusion that the numbers are a result of better detection, there is a lack of clinical data, such as the proportion of patients in each tumour-size group who underwent neck imaging and fine-needle aspiration biopsy.

The report also suggests the higher rates of thyroid cancer could be linked to greater exposure to radiation associated with medical scanning equipment.

How, along with co-author Dr. Roger Tabah, said the results point to the need for greater research, saying "specific and sensitive markers -- especially molecular and genetic -- is urgently needed to further understanding of the basic biology of each subgroup and variant of papillary thyroid carcinoma."

How said the results should be received with caution.

"I keep telling my patients that if you are bound to get cancer and you have a choice, I would pick (thyroid cancer) because in the majority of cases it is curable," How said.

"Even if there is an increasing trend or frequency, the majority of these patients are treatable and curable and their outlook is excellent."