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Breast cancer is the most common cancer among women and the second leading cause of cancer deaths in women in the United States. The American Cancer Society estimates that a woman in the United States has a 1 in 7 chance of developing invasive breast cancer during her lifetime [1]. Currently, finding breast cancer early and treating it are the most important strategies to fight this disease. The earlier the cancer is diagnosed, the greater the chance for successful treatment [2], since more treatment options are available and a complete recovery is more likely. Mammography is commonly used to look for breast disease, which is a specific type of imaging that uses a low-dose X-ray system to detect tumors or other abnormalities in the breast. It can be used either for screening or for diagnostic purposes in evaluating a breast lesion. Mammography plays a key role in early detection of breast cancers, as it can show changes in the breast up to two years before a patient or physician can feel them. However mammographic images are not always enough to determine the existence of a benign or malignant disease with certainty. If a finding or spot on the image seems suspicious, patients are usually recommended for a breast biopsy procedure. A breast biopsy is the removal of a sample of breast tissue for examination and is the only definitive way to determine if an abnormality detected on breast examination or mammogram is benign or malignant. Open surgical biopsy and needle biopsy are two commonly used biopsy procedures for the diagnosis of breast lesions. Open surgical biopsy has traditionally been used for breast cancer diagnosis. This procedure is performed in the operating room, and requires general anesthesia. The surgeon makes an incision in the breast and removes a tissue lump from the suspicious region. Needle biopsy is a minimally invasive biopsy procedure for obtaining a sample from the breast lesion. The physician makes a small skin incision through which a needle is placed into the lesion to obtain tissue samples for analysis.
Compared to open surgical biopsy, needle biopsy is less invasive, less expensive, faster, and requires a shorter time for recovery. Each year, about one million needle biopsies are performed in the United States for the diagnosis of breast cancer [3]. However, the sampling accuracy of needle biopsy is limited because only a few small pieces of tissue are sampled in the suspicious mass, and it is very difficult to verify that the samples are removed from the cancerous tissue site because two-dimensional imaging is used to guide the needle into a three-dimensional mass. This results in a 1 – 7 % false negative rate [4] and 9 – 18% of patients having to endure repeat biopsies [5,6]. In addition, about 80% of all biopsies done in the U.S. are benign (not cancerous), according to the American Cancer Society, which means a large number of benign tissues are unnecessarily removed. Given the lifetime probability that a woman has to undergo a breast biopsy procedure and the emotional and physical costs to the patient, it is critical to improve the sampling accuracy of this minimally invasive diagnostic procedure. Our goal is to incorporate an optical probe (based on optical spectroscopy techniques) into the image-guided biopsy procedure, to quickly and non-destructively identify the tissue type (normal, benign and malignant) at the needle tip prior to biopsy. A positive reading from the optical measurement will increase the likelihood that a biopsy is being sampled from the tumor site. If the optical measurement reads negative, then the needle can be repositioned (along the needle track) to a new place until the measurements reads positive. Currently 6 – 24 biopsies are taken during a core needle biopsy procedure. If the optical method can maximize sampling from tissue sites that are most likely to be cancerous, and minimize unnecessary removal of many normal tissues, it could make this procedure more accurate, less traumatic to the patient and also reduce the number of biopsies that need to be processed in order to obtain a confirmatory diagnosis. Additionally, if optical spectroscopy proves to be an effective way of identifying tumor sites, it can be incorporated into much smaller needles than that used in the Mammotome or Suros biopsy devices (for example, the 21 gauge needles used for fine needle aspiration) and thus make this procedure as minimally invasive as possible. We are currently developing two different types of optical technologies for breast cancer diagnosis during image guided core needle biopsy. These technologies differ with respect to the molecules in the tissue that they probe, their sensing volume, and the instrument and sensor design required for implementing them in a clinical setting. The first technology, based on ultraviolet-visible fluorescence and diffuse reflectance spectroscopy [7-10] has high chemical specificity, while that based on near infrared frequency domain photon migration techniques (FDPM) [11] has a significantly greater sensing depth in tissue. We are developing model-based algorithms based on a physical description of light transport in tissue [12] to extract the underlying biochemical, physiological and structural properties of tissue from the optical data that are diagnostic of breast cancer. Our goal is to develop and test these technologies independently. Ultimately we hope to combine these complementary technologies for the diagnosis of breast cancer. We have developed fiber optic probes that interface these technologies to the tissue to be sampled during core needle biopsy. These fiber probes are compatible with the vacuum-assisted biopsy needle (Suros Atech 9 gauge needle)) employed for image-guided breast biopsy.
Clinical trials are currently underway to test the feasibility of using the optical sensors and instruments for diagnosing breast cancer in near real-time during a clinical breast biopsy procedure. Several more years of system improvement, followed by clinical trials will be required to fully prove this technology before it is ready to be used interactively in the diagnosis of breast cancer. If this technology can improve the diagnostic efficacy of breast core needle biopsy, it will potentially reduce the number of missed cancers and repeat biopsies each year, thus significantly alleviating the physical and emotional costs to thousands of women undergoing this diagnostic procedure. References
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