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Ontario Cancer Facts

Endometrial cancer starting to rise in younger women in Ontario

Oct 2019

 

  • Endometrial cancer incidence (rate of new cases) has started increasing in women ages 30 to 49 in Ontario, which is consistent with trends observed in other countries.
  • Rising incidence likely reflects changes in the occurrence of risk factors for endometrial cancer, particularly hormone replacement therapy and obesity.
  • Endometrial cancer is more common in women age 50 and older, so it is important to track this cancer’s rising incidence in younger and older women, and learn more about its risk factors.

Endometrial cancer incidence (rate of new cases) rose in younger women ages 30 to 49 at 3.6% per year from 1997 to 2016 in Ontario, which is consistent with patterns observed in other countries. The incidence rate for endometrial cancer increased in this age group from 5.7 per 100,000 in 1997 to 11.3 per 100,000 in 2016.

Source: Ontario Cancer Registry, 2018 (Cancer Care Ontario)
Notes: Incidence rates are standardized to the age distribution of the 2011 Canadian population. Endometrial cancer (ICD-O-3 C54.1 with histologies 8010–8573). Incidence rates have been adjusted to adhere to the International Association of Cancer Registries (IACR) standards for counting multiple primary cancers, to allow for direct comparisons of incidence rates over time. The denominator has not been adjusted to reflect proportion of women who have had hysterectomies to remain consistent with other Ontario and Canadian published reports.

Endometrial cancer incidence rates, by age group, Ontario, 1981–2016
Year of diagnosis Ages 30-49 Age 50+
1981 8.4 68.0
1982 7.7 68.3
1983 9.0 66.5
1984 7.9 63.3
1985 7.3 64.9
1986 8.3 60.2
1987 8.4 61.3
1988 6.7 58.6
1989 5.2 54.4
1990 6.0 55.1
1991 7.0 58.1
1992 7.2 57.8
1993 6.6 58.1
1994 5.7 57.4
1995 6.4 53.2
1996 6.5 57.7
1997 5.7 57.1
1998 6.2 55.2
1999 6.5 56.2
2000 6.7 58.7
2001 6.3 58.9
2002 6.4 58.4
2003 6.4 60.2
2004 8.1 60.6
2005 6.6 58.7
2006 8.0 63.1
2007 7.8 63.2
2008 9.4 63.5
2009 9.0 67.8
2010 10.0 74.6
2011 9.3 77.2
2012 11.2 79.7
2013 9.1 75.1
2014 9.1 75.7
2015 11.9 78.4
2016 11.3 81.9

Source: Ontario Cancer Registry, 2018 (Cancer Care Ontario)
Notes: Incidence rates are standardized to the age distribution of the 2011 Canadian population. Endometrial cancer (ICD-O-3 C54.1 with histologies 8010–8573). Incidence rates have been adjusted to adhere to the International Association of Cancer Registries (IACR) standards for counting multiple primary cancers, to allow for direct comparisons of incidence rates over time. The denominator has not been adjusted to reflect proportion of women who have had hysterectomies to remain consistent with other Ontario and Canadian published reports.

Although endometrial cancer incidence is increasing in women ages 30 to 49, it is still mostly diagnosed in those who are post-menopausal (age 50 and older). The incidence rate of endometrial cancer in post-menopausal women is much higher than in younger women and has been increasing over the last few decades. From 1990 to 2007, endometrial cancer incidence increased significantly at 0.6% per year in this older age group. It then increased sharply and significantly from 2007 to 2011 (5.9% per year) and levelled off from 2011 to 2016.

Endometrial cancer is cancer of the endometrium, which is the lining of the uterus. The most important risk factor for endometrial cancer is being exposed to more estrogen than progesterone. Several reproductive and hormonal factors affect endometrial cancer risk by increasing or decreasing exposure to estrogen. Examples of factors that affect this estrogen-progesterone balance and protect against endometrial cancer include having more children, using combined estrogen-progesterone birth control pills and late onset of the first menstrual period. Going into menopause late increases the risk of endometrial cancer.

Because it can cause greater estrogen production, being overweight or obese is another factor that can increase the risk of endometrial cancer in those who have never used HRT. Rising rates of obesity over the last several decades is likely contributing to the increasing incidence of endometrial cancer in Ontario.

Hormone replacement therapy (HRT) can also affect endometrial cancer risk, although the relationship between HRT and this type of cancer is complex. Using estrogen-only HRT increases endometrial cancer risk, but combination progesterone-estrogen HRT reduces the risk of estrogen-induced endometrial cancer, depending on how long it is used for. Changes in how much and what types of HRT are used (i.e., estrogen-only or combination progesterone-estrogen) make it challenging to identify and measure important connections between HRT and endometrial cancer. A lack of detailed population-based data on HRT use in Ontario adds further challenges.

Given the continued increase in obesity and a potential lag time between HRT use and the development of endometrial cancer, it is important to continue tracking the incidence trends for this cancer in older and younger women. More research is needed to fully understand the development and prevention of endometrial cancer.

References

  1. Wartko P, Sherman ME, Yang HP, et al. Recent changes in endometrial cancer trends among menopausal-age US women. Cancer Epidemiol. 2013;37:374–7.
  2. Lortet-Tieulent J, Ferlay J, Bray F, et al. International patterns and trends in endometrial cancer incidence 1978–2013. JNCI. 2018; 110(4):354–61.
  3. Cancer Care Ontario Cancer Risk Factors in Ontario: Evidence Summary. Toronto, Canada, 2013. Available at https://www.cancercareontario.ca/en/statistical-reports/cancer-risk-factors-ontario-evidence-summary-0.
  4. Manson JE, Chlebowski RT, Stefanick ML, et al. Menopausal hormone therapy and health outcomes during the intervention and extended poststopping phases of the Women’s Health Initiative randomized trials. JAMA. 2013;310(13):1353–68.