News – 3 August 2008
Women in more danger than men
The age-standardised incidence of cancer increased in women by 7 per cent, while in men it has been unchanged over the last 10 years, according to the Thyroid Cancer in New South Wales 2008 report by Professor Jim F. Bishop, the CEO of the Cancer Institute NSW.
“Overall, however, men are 1.6 times more likely to be diagnosed with cancer than women,” he said. “There were 34,227 new cases of cancer diagnosed in NSW in 2005, with a median age at diagnosis of around 67 years.
“Cancer of the thyroid differs substantially from the broad experience from all cancers above. In the last 10 years the incidence of thyroid cancer has increased by 40% in males and 84% in females, with 650 new cases in NSW in 2005 with a predominance of women effected.
“The report is, therefore, very timely to focus on the quite specific issues surrounding this disease. The report reveals that the median age at diagnosis was around 50 years.
“The dramatic increase in incidence, especially in women, has been associated with the pathological sub-types of papillary adenocarcinoma and papillary microcarcinoma. Much of the increase in females has been localised cancer.
“Fortunately, overall five-year survival was good at 94% in recent years but much better at 98% if the disease was localised at the time of diagnosis.
“The report discusses the possible factors related to the increasing incidence of thyroid cancer. The information contained in this report allows better planning and management of the disease and raises awareness of this type of cancer.”
According to an executive summary of the report, thyroid cancer refers to cancer of the thyroid gland located in the neck. Thyroid cancer is not one of the most common cancers; ranking 9th in women and only 21st in males, but it is interesting as the incidence has increased consistently over the last 10 years, particularly in women.
The age-standardised incidence of thyroid cancer is more than three times higher in females than males, and it is increasing in females at almost twice the rate it is in males.
The reasons for this gender difference remains unclear, however it may be partly due to an increased incidence of thyroid disease in females and subsequent thyroid related surgical procedures, resulting in identification of smaller incidental cancers at a higher rate in women.
The age profile of thyroid cancer cases also differs by gender. In males, almost 60% of cases are identified in those over 50 years of age. However, the age distribution amongst females is different, with more than 55% of cases occurring in women younger than 50 years.
Risk factors for thyroid cancer include chronic iodine deficiency from diets low in iodine, and possibly diets high in soy-based products and cruciform vegetables.
Exposure to radiation, either medically or via nuclear accidents, is another well documented risk factor for thyroid cancer.
There is also considerable geographic variation in thyroid cancer incidence around the globe, with ethnic and geographic disparities most probably due to lifestyle and environmental factors, especially iodine deficiency.
Age and sex adjusted incidence is higher for major cities than other geographical areas in New South Wales.
However, mortality is similar between all geographic groups. The most socio-economically advantaged group has a higher incidence of thyroid cancer, compared with more disadvantaged groups. However, mortality is similar between all socio-economic groups.
Australia has a consistently higher incidence of thyroid cancer than less developed countries, but a lower mortality rate. The rate of thyroid cancer is higher in the non-English speaking-born population in New South Wales, compared with the Australian-born and overseas born English-speaking population.
Around two-thirds of thyroid cancer cases are diagnosed when localised to the thyroid, around 20% have regional spread, but only 3% have distant metastasis or secondary thyroid cancer. Higher five-year relative survival for patients with localized thyroid cancer (98.1%), compared with regional (93.3%) and distant (32.7%) cancer, suggests that early detection is important to maintaining low mortality rates from thyroid cancer.
Other highlights in the report include:
- It is estimated that one in 280 males and one in 92 females are at risk of developing thyroid cancer by 75 years of age.
- Treatment for thyroid cancer is tailored to the individual’s cancer type, stage and location.
- Although some risk factors are well established, most studies attribute the increase in thyroid cancer to the increase in papillary carcinomas.
- Cases were selected from NSW CCR-based topography codes C73.
- Over the past 10 years, new cases of thyroid cancer have risen at an average annual rate of 6.3 per cent.
- Since 1972, there has been an increase in the proportion of new cases diagnosed with a localised degree of spread.
- Major city areas do not have significantly higher mortality rates, although they do have significantly higher incidence rates.
- The incidence of thyroid cancer in NSW is expected to remain stable in males over the next two years but an increase by 9 per cent in females.
- The incidence of thyroid cancer is steadily increasing each year and most of this increase is in papillary carcinomas.
Reference:
Stavrou E, Baker D, McElroy H, Bishop J. Thyroid Cancer in New South Wales. Sydney: Cancer Institute NSW. Sydney, Australia,
April 2008. Published by the Cancer Institute NSW, April 2008.
MORE INFORMATION:
Cancer Institute NSW
www.cancerinstitute.org.au/
www.cancerinstitute.org.au/cancer_inst/publications/pdfs/em-2008-03-thyroid-cancer-in-nsw.pdf