Recent Incidence Rates and Trends of Breast Cancer in the USA
In this post, we will be looking at both actual and estimated incidence rates for breast cancer in the United States.
Breast cancer is the most common type of female cancer in the United States (excluding some types of skin cancers).
Despite huge improvements in screening programs, early detection and targeted treatment, breast cancer remains a global health concern.
graphs and statistics, Doc?
Some Facts and Figures and Recent Statistics
According to the National Cancer Institute (SEER statistics), an estimated 252,710 women will be diagnosed with breast cancer in 2017.
Furthermore, 230,815 American women were actually diagnosed with breast cancer in 2013. Over 3.1 million American women have been affected by breast cancer as of March 2017.
It has been estimated that around 30% of all female cancers in 2017 will be breast cancer.
However, it is not all bad news. Based on the SEER statistics between the years 2007 to 2013, the percentage of women surviving for 5 years after a breast cancer diagnosis is 89.7%.
Female Diagnosed Breast Cancer Cases
Trends in Incidence Rates from 1995 to 2014
The Rise in Incidence Rates of Breast Cancer in the 1990s (US)
According to SEER statistics, between the years 2010 to 2014, the breast cancer incidence rate was 124.9 per 100,000 women per year.
However, from our line graph (above) we can see that there have been some interesting trends in the rates of breast cancer over the past 19 years.
The age-adjusted increase in breast cancer incidence rates during the 1990s was around 0.5% per year. Furthermore, this rise was especially evident in women over the age of 50.
This rise in breast cancer incidence rates in the 1990s may be explained by a number of factors according to a 2007 research study and these include:-
- Widespread use of Hormone Replacement Therapy (HRT) following menopause.
- Increase in mammographic screening
- Changes in reproductive factors
- Change in environmental factors or diet
Kaiser Permanente Northwest (KPNW) Study
Kaiser Permanente Northwest (KPNW), a large US health plan, also used statistics to examine breast cancer incidence rates. This research used tumor registry, clinical, pathology and pharmacy data.
This large study reflects the results of incidence trends from the National Cancer Institute SEER results.
The study concluded that since 1980, trends in the increase of breast cancer incidence reflect increased patterns for mammography screening and use of HRT.
Interestingly, between 1980 and 2001 breast cancer incidence rates for women under 45 years were stable. However, for women between 45 to 59 years and those 60 years or older, incidence rates rose around 50% between 1980 and 2001.
The first wave of increased rates was attributed to the increase in screening mammography during the early 1980s.
The second rise in breast cancer incidence rates throughout the 1990s corresponded to increased use of HRT, especially combined therapy.
The BIG decrease in Breast Cancer Rates from mid-2002 (US)
Of all the reasons suggested above for the rise in breast cancer incidence rates in the 1990s, Ravdin (et al) suggest that only the use of HRT changed dramatically between 2002 and 2003.
As we can see from the graph, the sharp decrease of breast cancer incidence rates began in mid-2002. Many studies suggest that this decrease is linked to the release of a research trial from the Women’s Health Initiative (WHI) highlighting the health risks of HRT.
According to the WHI, the use of estrogen-progestin (combination) therapy significantly increased the risks of coronary heart disease and breast cancer.
With the widely publicized results of the WHI report on HRT therapy, many women panicked and by the end of 2002, the use of HRT had dropped by 38% in the US. It is estimated that around 20 million fewer prescriptions were written for HRT in 2003 than in 2002.
A further study highlights that the sharp decrease in incidence rates of breast cancer from 2002 to 2003 was most prevalent in women between 50 to 69 years old and with ER+ tumors. This suggests that HRT therapy affect Estrogen positive tumor growth.
However, this research also suggests that this period of a steep decline in breast cancer incidence rates also coincides with ‘a saturation’ in screening mammography.
Doc?
A Little Update on Hormone Replacement Therapy (2016)
A huge, new, research study by the Institute of Cancer Research, London followed 100,000 women over 40 years.
The study, published in 2016, awakens new concerns about Hormone Replacement Therapy (HRT) once more.
This research suggests that previous investigative research have underestimated the increased risk of breast cancer with the use of combined HRT by up to 60%.
Furthermore, women who take combined HRT treatment are 2.7 times more likely to develop breast cancer.
Ductal Carcinoma In-Situ and Invasive Breast Cancer Rates
What is Ductal Carcinoma In-Situ (DCIS)?
Ductal carcinoma in situ (DCIS) is a very early stage non-invasive breast cancer. DCIS is the most common in-situ breast cancer diagnosed.
A diagnosis of DCIS indicates that breast carcinoma is present, but has not yet infiltrated the lining of the breast ducts. There are many different types and grades of DCIS, most of which are not life-threatening. The Prognosis for DCIS is excellent.
Prior to 1980, DCIS was rarely diagnosed. But with advances in breast cancer screening procedures and increased participation in screening mammography DCIS is more frequently diagnosed.
What is Invasive Cancer?
Invasive breast cancer, unlike in-situ cancer, is when cancer has spread beyond the ducts or glands and grown into the breast tissue. This cancer can then infiltrate into local lymph nodes and beyond.
Invasive (or infiltrating) breast cancer is a more advanced stage than an in-situ carcinoma. Women in the US are more likely to be diagnosed with invasive cancer than in-situ cancer.
I do have some graphs…
Comparison of estimated cases of DCIS and Invasive Cancer Graphs for 2016 – 2017 (US)
We can see from the above two graphs that the estimated cases of invasive breast cancer for 2016 to 2017 are much larger than those of DCIS.
There are an estimated 60,290 new cases overall of DCIS compared with 231,840 new cases of invasive cancer, in the US, for the year 2016.
That is to say that around a quarter of all new breast cancer cases will be detected at a very early stage. This is good news as the prognosis is excellent.
Another interesting factor is that age at diagnosis does play a role. We can clearly see that the general trends in the two graphs are fairly similar.
Women under 40 years have the lowest incidence rate in general for both types of breast cancer. Indeed, less than 5% of women diagnosed with cancer are under 40 years. However, often the tumors in younger women are more aggressive.
The risk of breast cancer does increase as a woman gets older. The average age of diagnosis for female breast cancer in the US is 62 years, although this varies according to race and ethnicity.
Further Reading and Interesting Posts
- For a more in-depth look at Breast Cancer: Age, Incidence and Mortality Rates
- For a more in-depth look at Breast Cancer: Race/Ethnicity, Incidence and Mortality Rates
- DCIS: Prognostic factors and survival rates
Back to the full index for Breast cancer Incidence and Mortality posts or to the brand new homepage.
Note: There is also a new post on Lung Cancer Incidence rates.
Below is some of the original information from this post, that has recently been updated. Obviously, some of the data and information is a little dated now, but still holds value in examining trends in breast cancer incidence rates over the years.
Breast cancer tumors at the time of the first detection tend to be small and ‘node-negative’
In Canada, studies have shown that for women aged 50-69 years, an invasive tumor of less than 1.5 cm is detected about 54% of the time.
Furthermore, tumors with a node-negative status are detected around 77 % of the time. Node negative means that cancer has not spread into the lymph nodes.
This means that even if breast carcinoma is not diagnosed at the DCIS stage, the odds of discovering and successfully treating breast cancer at an early invasive stage are still very good.
The relative rates of DCIS and invasive breast cancer remain about the same
The graph (to the right here) examined relative rates of DCIS and invasive breast cancer between 1996 and 2003 in the USA.
Interestingly this graph demonstrates that the total number of breast cancer and DCIS cases in the US tended to hover around 6000 women per year during that time period. (NB: The corresponding drop in figures between 2002 and 2003).
Overall, the ratio of DCIS to breast cancer for all age groups appears to be between 15% and 20%.
Breast Cancers and DCIS diagnosed by mammography by age 10 year age group, in the USA
Initial screening for breast cancer as categorized by age groups demonstrates that the earlier in age screening begins, the higher the rate of DCIS detected.
In our graph to the right, one can observe that DCIS is most commonly diagnosed between the ages of 40 and 59 and is very rare in women under 30.
This gives further support to the theory that breast cancer screening should begin at age 40 and continue through the ’50s.
Most of the time, DCIS is a better diagnosis and prognosis than invasive cancer and results in fewer mortalities.
In North America, initial screening procedures typically identify DCIS about 30% of the time for women over 40, as compared to 70% breast cancer diagnosis.
DCIS rates have increased since the 1990s, while invasive breast cancers are in decline
Invasive breast cancer rates did not increase during the late 1980s and have, in fact, declined since 2000.
The graphic to the right clearly demonstrates both the upward trajectory of DCIS detection in the late 1980’s coinciding with improved screening procedures and a peak and subsequent decline in invasive breast cancer diagnosis since around 1998. The line graph shows the incidence rates of DCIS and invasive breast cancer between the years of 1975 to 2005.
However, during this period the rate of Ductal Carcinoma In-Situ (DCIS) diagnosis has increased by 200%.
Interestingly, the use of screening mammography increased by approximately 250% during the same period, although with a peak increase much sooner than the increase of DCIS detection.
DCIS is frequently ‘over-diagnosed’
Over-diagnosis is a term now frequently associated with DCIS.
Over-diagnosis means that the DCIS would not have otherwise been detected during a woman’s lifetime without screening. In other words, the DCIS would not have posed any health problem.
Between 15% and 18% of DCIS diagnosis are thought to be over-diagnosed.
The concern is that a majority of DCIS cases are treated by surgery. In some instances, DCIS has been treated by mastectomy when it may be completely unnecessary.
REFERENCES:
- American Cancer Society. Breast Cancer Facts & Figures 2015-2016. Atlanta:
American Cancer Society, Inc. 2015. - Ravdin PM, Cronin KA, Howlader N, Berg CD, Chlebowski RT, Feuer EJ. (et al). (2007) The Decrease in Breast-Cancer Incidence in 2003 in the United States
N Engl J Med 2007; 356:1670-1674April 19, 2007 http://www.nejm.org/doi/full/10.1056/NEJMsr070105#t=article
