Dr. Bray Links

Monday, February 29, 2016

Mammogram-Induced Breast Cancer Incidence and Mortality


Assuming there are 80 million women over the age of 40 in the United States, the current use of annual mammograms causes approximately 100,000 to 200,000 cases of breast cancer (due to the ionizing radiation), while saving the lives of 774,400 women. Getting a screening mammogram every 2 years (rather than annually) reduces the risk of radiation-induced breast cancer 5-fold. A regular clinical breast exam is still advised since many breast cancers can be silent on mammogram.

"Annual screening of 100 000 women aged 40 to 74 years was projected to induce 125 breast cancer cases (95% CI, 88 to 178) leading to 16 deaths (CI, 11 to 23), relative to 968 breast cancer deaths averted by early detection from screening. Women exposed at the 95th percentile were projected to develop 246 cases of radiation-induced breast cancer leading to 32 deaths per 100 000 women. Women with large breasts requiring extra views for complete examination (8% of population) were projected to have greater radiation-induced breast cancer risk (266 cancer cases and 35 deaths per 100 000 women) than other women (113 cancer cases and 15 deaths per 100 000 women). Biennial screening starting at age 50 years reduced risk for radiation-induced cancer 5-fold."


Ann Intern Med. 2016 Feb 16;164(4):205-14. doi: 10.7326/M15-1241. Epub 2016 Jan 12.
Radiation-Induced Breast Cancer Incidence and Mortality From Digital Mammography Screening: A Modeling Study.
Miglioretti DL, Lange J, van den Broek JJ, Lee CI, van Ravesteyn NT, Ritley D, Kerlikowske K, Fenton JJ, Melnikow J, de Koning HJ, Hubbard RA.

Exposure to ionizing radiation from repeated mammography examinations may increase breast cancer risk (1, 2). Radiation-induced breast cancer incidence and mortality associated with recommended screening strategies are suggested to be low relative to breast cancer deaths prevented (3–5). However, prior projected population risks were based on exposure from screening only and assumed only 4 standard views per screening examination at the mean radiation dose. Evaluations of screening programs should consider full episodes of care, including diagnostic work-up prompted by an abnormal screening result (6). False-positive recalls, breast biopsies, and short-interval follow-up examinations are relatively common in the United States and add radiation exposure from diagnostic mammography (7). Some subgroups of women, such as obese women and those with dense breasts, are more likely to have additional evaluations (7–9), which may increase their risk for radiation-induced cancer.

When risk for radiation-induced breast cancer is being evaluated, it may also be important to consider variation in radiation dose from a single examination. Examinations vary in the number of views performed and dose per view; therefore, some women receive more than the mean dose. The American College of Radiology Imaging Network DMIST (Digital Mammographic Imaging Screening Trial) found an average radiation dose of 1.86 mGy to the breast from a single digital mammography screening view (10), but dose per view varied from 0.15 to 13.4 mGy (Supplement), and 21% of digital screening examinations used more than 4 views (10). Radiation dose is strongly correlated with compressed breast thickness; thus, women with large breasts tend to receive greater doses per view and may require more than 4 views for complete examination (10, 11). Women with breast augmentation receive implant-displacement views in addition to standard screening views, which doubles their radiation dose (12). Women may have repeated views because of movement artifacts or improper breast positioning.

We estimated the distribution of cumulative radiation dose and associated breast cancer risk from full screening episodes to identify subgroups of women who may have a greater risk for radiation-induced cancer because they have factors contributing to greater doses per examination or frequent false-positive screening results that lead to additional radiation exposure from subsequent diagnostic work-up. Using population-based data from the Breast Cancer Surveillance Consortium (BCSC) (13), we estimated the probability of a false-positive screening result followed by additional imaging evaluation, short-interval follow-up, or biopsy. We used data from the BCSC, DMIST, and other sources in 2 simulation models to estimate radiation exposure and radiation-induced breast cancer incidence and mortality associated with 8 potential screening strategies with different starting ages (40, 45, or 50 years) and screening intervals (annual, biennial, or a hybrid strategy).

http://annals.org/article.aspx?articleid=2480762

Biennial strategies were consistently the most efficient for average-risk women. Biennial screening from age 50 to 74 years avoided a median of 7 breast cancer deaths versus no screening; annual screening from age 40 to 74 years avoided an additional 3 deaths, but yielded 1988 more false-positive results and 11 more overdiagnoses per 1000 women screened. Annual screening from age 50 to 74 years was inefficient (similar benefits, but more harms than other strategies). For groups with a 2- to 4-fold increased risk, annual screening from age 40 years had similar harms and benefits as screening average-risk women biennially from 50 to 74 years. For groups with moderate or severe comorbidity, screening could stop at age 66 to 68 years.

http://annals.org/article.aspx?articleid=2480763

Recommendations: The USPSTF recommends biennial screening mammography for women aged 50 to 74 years. (B recommendation)The decision to start screening mammography in women prior to age 50 years should be an individual one. Women who place a higher value on the potential benefit than the potential harms may choose to begin biennial screening between the ages of 40 and 49 years. (C recommendation)The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of screening mammography in women aged 75 years or older. (I statement)The USPSTF concludes that the current evidence is insufficient to assess the benefits and harms of digital breast tomosynthesis (DBT) as a primary screening method for breast cancer. (I statement)The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of adjunctive screening for breast cancer using breast ultrasonography, magnetic resonance imaging (MRI), DBT, or other methods in women identified to have dense breasts on an otherwise negative screening mammogram. (I statement)

http://annals.org/article.aspx?articleid=2480757




http://www.cancer.org/acs/groups/content/@research/documents/document/acspc-046381.pdf

Screening Test
Sensitivity
Specificity
Physician Breast Exam
57%
97%
Self Breast Exam
12%
unknown
Mammography – average breasts
69%
91%
Mammography – dense breasts
30%
unknown
Ultrasound
36%
86%
Breast MRI
88%
68%
PET
96%
77%
Thermography
97%
93%

Sensitivity = If a person has breast cancer, how often will the test be positive (true positive rate)?

Specificity = If a person does not have breast cancer how often will the test be negative (true negative rate)?

http://www.ncbi.nlm.nih.gov/pubmed/26229503
http://www.ncbi.nlm.nih.gov/pubmed/17356964
http://www.ncbi.nlm.nih.gov/pubmed/26889531
http://www.ncbi.nlm.nih.gov/pubmed/10880551
http://www.ncbi.nlm.nih.gov/pubmed/25448668

CONCLUSIONS: Whereas the majority of patients had image-detected breast cancer, a significant number of image-screened patients presented with palpable disease, which were more aggressive cancers. Until imaging techniques are refined, self breast exam (SBE) and clinical breast exam (CBE) remain important for breast cancer diagnosis.

http://www.ncbi.nlm.nih.gov/pubmed/22160521

CONCLUSION: Based on the results of this study involving 1008 subjects for screening of breast cancer, thermography turns out to be a very useful tool for screening. Because it is non-contact, pain-free, radiation free and comparatively portable it can be used in as a proactive technique for detection of breast carcinoma.

http://www.ncbi.nlm.nih.gov/pubmed/25448668

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