Personalising Breast Screening With Breast Density and Other Risk Factors
Breast cancer was the attributed cause of death for approximately 521,000 individuals worldwide in 2012 and it is the leading cancer-related cause of death for women in Australia
More and more incidents of breast cancer are being detected each year and whilst this fact held in isolation may sound distressing, the truth is that mortality rates are declining. There is a strong correlation between early detection and rate of survival and this is why breast screening is such an important tool in the fight against breast cancer.
Women are recommended to undergo breast screening every 1 to 2 years. This is fundamentally a blanket recommendation applied to all women over the age of 40. But we know that no two woman are the same and because of this, every woman has a different set of risk factors for breast cancer.
Age is a major risk factor and perhaps the most prominent, it is already used by BreastScreen Australia to segment women into higher risk categories. As an example, women aged 70-74 are actively invited to two-yearly screening mammograms. Other risk factors include breast density, obesity, history of breast biopsy and family history of cancer. Notably, breast density is of increased importance. Here we have a risk factor that not only dramatically increases the chance of developing breast cancer (extremely dense breast tissue can increase the rate of breast cancer by up to 6 times) but also makes detection of such cancer more difficult. Breast density is also the main cause of false-negative results in breast screening.
Breast density is such an important factor that a number of states in the USA are adopting legislation which requires care providers to inform women and talk to them about their breast density (in the form of a BI-RADS score which scores breast density on a scale from A to D). Women can then choose to undergo more frequent mammograms or an MRI if they are at higher risk.
When devising a screening program there are a few factors that need to be considered. The ideal solution would be cost effective but also feature a high detection rate and an as low as reasonably possible dose of radiation.
If we could use risk factors to determine the most effective interval for each woman we could develop a cost-effective screening cycle that results in less unecessary doses for those who are at low risk and more frequent for those at higher risk so as to increase the chance of early detection.
A study titled “Personalizing mammography by breast density and other risk factors for breast cancer: analysis of health benefits and cost-effectiveness“ by Cummings et. al. shows that this approach is viable. The researchers modelled the most cost-effective interval for mammography screening based on the BI-RADS scoring system, age, family history and history of biopsy.
For the woman who have a high BI-RADS breast density score and who should receive more frequent screening, the issue then is to use screening techniques which require as low radiation dose as possible while still providing an accurate screening and diagnostic outcome. Fortunately, technology in this area is evolving. Multi-modailty approaches which combine ultrasound or MRI with mammography have been shown to improve diagnostic performance.
Another recent advance in mammography technology is that of photon counting. Photon counting as the name suggests, is a detector which counts individual photons. It reduces the number of conversions of information between then x-ray generator and the final image and in doing so, reduces the amount of noise and consequently the amount of radiation required to capture an image.
Photon counting is a technology currently only available in the Philips MicroDose solution. A mammography unit designed to provide superior diagnostic performance at the lowest dose possible. It features a multi-slit detector which drastically eliminates scatter radiation resulting in a further elimination of noise and dose.
The MicroDose solution also makes use of spectral imaging technology to provide an objective measure the density of breast. Spectral imaging uses different energy photons to get a better insight into the characteristics of breast tissue. It can provide women with a BI-RAD composition score which is not a subjective interpretation by a radiologist but based on mathematical formula. A consistent approach to classifying the density of breast tissue is an important step in using it as a risk factor for tailored screening programs.
Information and facts were gathered from:
Berg WA et. al.: “Combined screening with ultrasound and mammography vs mammography alone in women at elevated risk of breast cancer.”, JAMA BreastScreen Australia Website: http://www.cancerscreening.gov.au/internet/screening/publishing.nsf/Content/breastscreen-about Cancer Australia Website: http://canceraustralia.gov.au/affected-cancer/cancer-types/breast-cancer/breast-cancer-statistics Cummings et. al: “Personalizing mammography by breast density and other risk factors for breast cancer: analysis of health benefits and cost-effectiveness.”, Ann Intern Med Gretchen et. al: “Relationship Between Mammographic Density and Breast Cancer Death in the Breast Cancer Surveillance Consortium”, Journal of National Cancer Institude National Cancer Institute Website: http://www.cancer.gov/cancertopics/factsheet/detection/mammograms World Health Organization Website: www.who.int/mediacentre/factsheets/fs297/en/index.html
Disclosure: Imaging Solutions is a distributor for the Philips MicroDose product.