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*)
*initial diagnosis only-does not include metastatic recurrences
• 226,870 women and 2190 men in the US in 2012 for a total of 229,060 [American Cancer Society (ACS) Cancer Facts and Figures 2012]
• In US women diagnosed with breast cancer every 3 minutes
Non-Invasive Breast Cancer Incidence (Stage 0)
• 57,560 new cases of non-invasive in Situ breast cancer (Stage 0);
• includes DCIS -Ductal Carcinoma in Situ and LCIS-Lobular Carcinoma in Situ
Metastatic Breast Cancer Incidence
MBC incidence is the number of newly diagnosed cases of metastatic breast cancer in a given year.
• Statistics not collected. 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.
• 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 cancer cases
• 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 interview (http://www.youtube.com/watch?v=UoUftDNl4fo) 11/2009
• Quote from The Oncologist Journal "Prognostic and Predictive Factors in Early-Stage Breast Cancer" (May 2004) "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."
•Quote from Musa Mayer's Report: Silent Voices, 2006: "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."
Incidence rate is the number of new cases divided by the population at risk
Incidence Rate for all Invasive Breast Cancer (Stages I-IV*):
* includes initial diagnosis of Stage IV only, not metastatic recurrences
• 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]
Incidence Rate for MBC
• Statistics not collected