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Incidence and Incidence Rates


Incidence is the number of newly diagnosed cases in a given year.

Invasive Breast Cancer Incidence (Stages I, II, III, IV*)

The American Cancer Society’s estimates for breast cancer in the United States for 2016 are:

  • About 246,660 new cases of invasive breast cancer will be diagnosed in women.
  • About 61,000 new cases of carcinoma in situ (CIS) will be diagnosed (CIS is non-invasive and is the earliest form of breast cancer).
  • About 40,450 women will die from breast cancer.

*initial diagnosis only-does not include metastatic recurrences

Source: ACS, What Are the Key Statistics About Breast Cancer, retrieved October 2016

Metastatic Breast Cancer Incidence 

MBC incidence is the number of newly diagnosed cases of metastatic breast cancer in a given year.

Statistics are not collected for metastatic recurrences which comprise the larger portion of MBC cases. Statistics are only gathered for initial diagnosis of Stage IV metastatic disease. See: “Where is the Data? The Epidemiology of Metastatic Breast Cancer,” retrieved October 2016

Approximately 6-10% of new breast cancer cases are initially Stage IV or metastatic. This is sometimes called “de novo” metastatic disease, meaning from the beginning. For 2012 this means new cases of Stage IV were in the range of 13,776 – 22,096.

The number of metastatic recurrences are unknown, but are estimated to range between 20-30% of all existing breast cancerases. This figure is the subject of ongoing controversy. Below are excerpts from some experts papers and public comments. 

Dr. Joyce O’Shaughnessy estimated the rate to be 30% in developed countries [O’Shaughnessy, J. “Extending Survival with Chemotherapy in MBC” The Oncologist 2005:10]

Dr. William Gradishar of Northwestern University : “Breast cancer can become metastatic in roughly 30% of patients…” at 1:30 mark in this 11/2009 interview

“The poor outcome with the Halstedian approach, as well as the observation that 20%-30% of node-negative patients ultimately develop metastatic disease, led to the currently held micrometastatic paradigm. This paradigm asserts that many patients with early-stage disease have distant micrometastatic disease present at the time of diagnosis, putting them at risk for the later development of overt metastatic disease.” — The Oncologist Journal Prognostic and Predictive Factors in Early-Stage Breast Cancer (May 2004)

“Stage at initial diagnosis is a strong predictor of distant metastatic recurrence, with women diagnosed with cancer that is locally advanced, spread regionally beyond the breast, much more likely to recur than breast cancer diagnosed as localized, although as many as 30% of localized cancers ultimately do recur, and many of these will go on to develop distant metastases.” — Musa Mayer’s Report: Silent Voices, 2006.

Additional Insights on Metastatic Breast Cancer Recurrence 

For those with early stage breast cancer, what is the metastatic recurrence rate? Is it closer to 20% or closer to 30%? There are currently massive gaps in how people with metastatic breast cancer are counted–our cancer registries don’t track metastatic recurrences–something MBCN and its fellow MBC Alliance members are trying to change. There are certainly some who feel strongly the number is lower rather than higher. The following is from ACS Breast Cancer Facts and Figures 2013-14

Breast Cancer Survival and Stage at Diagnosis
 Relative survival rates are an estimate of the number of patients who will survive for a given time after a cancer diagnosis.  It differs from observed survival in that it accounts for deaths from other causes by comparing among cancer patient to survival among people of the same age and race who have not been diagnosed with cancer.  
 Based on the most recent data, relative survival rates for women diagnosed with breast cancer are:
  •  89% at 5 years after diagnosis
  • 83% after 10 years
  • 78% after 15 years

“Of course, women keep dying of MBC longer than 15 years after their initial diagnoses,” notes Musa Mayer, patient advocate and Member, Steering (Executive) Committee, Metastatic Breast Cancer Alliance. “According to SEER statistics:  18-year relative survival for patients diagnosed from 1990-1994 is 71% which takes us really close to the 30% figure. However, it’s important to bear in mind that none of these [HER2 positive] patients would have been offered Herceptin, not even in the metastatic setting.  With adjuvant Herceptin cutting recurrence rates in half, this is a big difference. Fewer hormonal options existed as well.

Unfortunately, Herceptin is not an option for all breast cancer patients.HER2 positive breast cancer--i.e., the subtype Herceptin targets–accounts for about 15 to 20 percent of all breast cancers;  ER/PR+; HER2-  is the most common subtype, accounting for 65% of breast cancer cases;  the triple negative subtype accounts for 15% of breast cancer cases.

Incidence Rate

Incidence rate is the number of new cases divided by the population at risk

Incidence Rate for all Invasive Breast Cancer (Stages I-IV)*

  • For all invasive BC: Declined from 1999-2003; stable since 2003 [SEER, 2011]
  • Rates “increased rapidly” between 1980-87 “due largely to greater use of mammography screening, leading to increased detection of breast cancers too small to be felt.” This inflates “the incidence rate because tumors are being detected 1 to 3 years” earlier.
  • Rates stabilized/slowed in 1990’s.
  • There was a sharp decrease in 2002-2003 “due to decreased use of menopausal hormones.”
  • Since 2003 rates have been stable. However, the population has been increasing.
  • For non invasive DCIS rates “rose rapidly during 80’s and 90’s,” due to mammography screening. “Since 1999 incidence of in situ cases have stabilized among women 50 and older, but continue to increase in young women.” [ACS Breast Cancer Facts, 2011-12]

* includes initial diagnosis of Stage IV only, not metastatic recurrences

Incidence Rate for MBC

  • Statistics not collected