Breast cancer is the most commonly occurring cancer in women and the lifetime risk (at age 85) of being diagnosed is approximately 1 in 10 [1], the highest probability out of all cancers. Breast cancer screening programs have been shown to decrease the mortality rates of women age 50-69 [2] due to detecting cancer at an earlier, treatable stage, however compliance is low due to a variety of reasons. While the understanding of the underlying causes and mechanisms leading to breast cancer is increasing, development of the disease is not fully understood. Hence, there has been a push to propose, develop and understand risk factors for the disease; which are defined as those characteristics that people with the disease have in common [3].
There is increasing attention to prevention as a means to reduce cancer incidence. Prevention interventions or therapies in turn rely on risk assessment programs to identify those women most likely to benefit from education and lifestyle changes. These programs are usually based either on interviews to identify ethnic, genetic, and lifestyle factors contributing to risk or on physical examination of the breast. For the latter it has been shown that the parenchymal density pattern observed in X-ray mammography can be used to assess an individual's risk. Extensive areas of dense, glandular tissue that are relatively radio-opaque are associated with higher breast cancer risk, with an odds ratio of 4 to 6 compared with women in whom the breast density is low owing to an abundance of adipose tissue. Near-infrared optical transillumination spectroscopy has been used previously to investigate the physiological properties of breast tissue. In this study, women were recruited who underwent recently X-ray mammography. The tissue density was assessed by a radiologist. The women then underwent optical transillumination spectroscopy, for which an instrument was developed that delivered visible and near-infrared light to the breast. After being transmitted through the breast craniocaudally in one of four quadrants, the spectrum from 625 to 1050 nm was measured. The spectra were used as input to a Principal Component Analysis (PCA) that used the corresponding mammographic density as the reference standard. The study group consisted of 92 women aged 39 to 72 years. Without further stratification for age, menopausal status, or measurement position, the PCA numerical model predicted the radiological assessment of tissue density in the mid 80% to low 90%.
Preventive oncology is in need of a risk assessment technique that can identify individuals at high risk for breast cancer and that has the ability to monitor the efficacy of a risk reducing intervention. Optical transillumination spectroscopy (OTS) was shown to give information about breast tissue composition and tissue density. OTS is non-invasive, and in contrast to mammography, uses non-ionizing radiation. It is safe and can be used frequently on younger women, potentially permitting early risk detection and thus increasing the time available for risk reduction interventions to assert their influence. Before OTS can be used as a risk assessment and/or monitoring technique, its predictive ability needs to be demonstrated and maximized through the construction of mathematical models relating OTS and risk. To establish a correlation between OTS and mammographic density, Principle Components Analysis (PCA), using risk classification, is employed. PCA scores are presented in 3D cluster plots and a plane of differentiation that separates high and low tissue density is used to calculate the predictive value. Stratificaiton of PCA for measurement position on the breast in cranial-caudal projection is introduced. Analysis of PCA scores as a function of the volunteer's age and body mass index (BMI) is examined. A small but significant correlation between the component scores and age or BMI is noted but the correlation is dependnet on the tissue density category examined. Correction of the component scores for age and BMI is not recommended, since a priori knowledge of a women's tissue density is required. Stratification for the center and distal measurement positions provides a predictive value for OTS above 96%.
Breast cancer is the most commonly occurring cancer in women. The lifetime risk of being diagnosed with breast cancer is approximately 1 in 10 thereby the highest out of all cancers. Breast cancer screening programs have been shown to decrease the mortality rates of women between ages 50-69, since cancers are detected at an earlier, more favourable stage. It is apparent that the development of breast cancer is a slow process following initial transformation of the breast tissue. Hence, there has been a strong effort within the research community to understand risk factors for the disease. Risk factors are defined as those characteristics that are more common in people with the disease when compared to the normal population. Quantification of an individual's breast cancer rate may lead that individual to modify her lifestyle and/or diet. Lifestyle changes could lead to a reduction in the incidence of breast cancer.
Anatomically, the presence of increased amounts of fibroglandular tissue raises the estimated risk by up to 6 fold (correct for age), hence representing one of the strongest known risk factors pertaining to the entire female population. In this study the relative area of mammographic densities within a mammogram will be used as a global risk assessment tool. It has been shown previously that quantification of water, lipids, haemoglobin and other tissue chromophores of the optically interrogated breast tissue, which also gives rise to the mammographic densities, is feasible through near-infrared spectroscopy. Thus, the hypothesis for this study is that optical transillumination spectroscopy provides consistent and/or complementary information to conventional mammography in quantifying breast tissue density.
Determining an individual’s cancer risk is an important step to increase the efficacy of screening procedures. Currently, breast cancer risk can be clinically assessed using tissue density patterns seen on standard x-ray mammography. These patterns reflect the ratio of glandular tissue to adipose tissue within the breast. Increased dense areas of glandular tissue indicate a higher risk category with an odds ratio of approximately 6. Near-infrared optical transillumination spectroscopy has been shown helpful in investigating physiological and anatomical properties of the breast tissue. Similarly the adipose and glandular tissue ratio responsible for the x-ray density pattern together with other optically active tissue chromophores can result in unique optical transillumination spectra. In this study we are considering patients who had standard mammograms and examine their breast tissue by optical transillumination spectroscopy in order to establish a correlation between the two techniques and therefore the ability of using transillumination for risk estimation. The transillumination spectra show haemoglobin, water and lipid absorption characteristics. Correlation between optical transillumination spectroscopy and mammographic density pattern are established through the use of Principal Component Analysis and Linear Discriminant Analysis. Preliminary, results indicate that x-ray dense tissue can be identified with a specificity and sensitivity above 0.87 each, for both post and pre-menopausal women.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.