Laser-based testing helps detect metastasis
ASHLEY N. RICE, ASHLEY.RICE@PHOTONICS.COM
BALTIMORE – A tissue-penetrating, laser-light-enhanced microscope accurately analyzes distinctive patterns of ultrathin collagen fibers in breast tumor tissue samples, which could help detect cancer’s spread.
The Johns Hopkins University technique uses crisscrossing optical images, made by shining a laser back and forth across a biopsied tissue sample a few microns thick, to measure minute changes in tumor connective tissue fibers. It could potentially be used with other tests to more accurately determine the need for lymph node biopsy and removal in women at risk of metastatic breast cancer.
“Our new diagnostic technique has the potential to help reassure thousands of breast cancer patients that their cancers have not spread to other organs, and could help them avoid the risks and pain currently involved in direct inspections of lymph nodes for the presence of cancerous cells,” said Dr. Kristine Glunde, the study’s senior investigator.
In what is believed to be the first study to measure minute changes in tumor connective tissue fibers, the researchers found that eight women whose cancers had spread beyond the breast through the body’s lymphatic system had about 10 percent more densely packed and radially spread out collagenous structural proteins than six women whose cancers had not yet spread. Collagen fibers in the nonmetastasized tumors, also obtained during breast biopsy, were more diffuse and arranged in a transverse or horizontal pattern. All 14 women in the study had aggressive, malignant breast cancer.
If these “proof of principle” findings hold up in testing now under way in hundreds more women with or without metastatic breast cancer, their new optical imaging tool could simplify testing for spreading disease and help people avoid unnecessary lymph node surgery, the researchers said.
Women with denser tumor fiber patterns stand a greater chance of needing lymph node biopsy and removal and inspection of such tissue for malignant cells, said Glunde, an associate professor at the Johns Hopkins University School of Medicine and the Sidney Kimmel Comprehensive Cancer Center.
Complications from lymph node biopsy and more invasive dissection include several risks, including pain, severe swelling, infection and leakage of lymph fluids around the armpit as well as arm stiffening, which can be permanent. In 2011, an estimated 230,000 Americans were diagnosed with invasive breast cancer, while another 57,000 were found to have noninvasive breast cancer.
For more than a decade, cancer imaging experts have known that fibrous connective tissue located between cancer cells changes and bunches together as tumors grow and disease spreads, said co-investigator Dr. Zaver Bhujwalla, a professor at Johns Hopkins and its Kimmel Cancer Center.
“Until now, however, we had no proof in principle that such minute and progressive changes outside cancer cells, in the tumor microenvironment or extracellular matrix, could be measured and potentially used to better guide our staging and treatment decisions,” said Bhujwalla, who also serves as director of the Johns Hopkins In Vivo Cellular and Molecular Imaging Center, where the latest study was performed.
It was in 2010 at ICMIC where Glunde, Bhujwalla and colleague Meiyappan Solaiyappan developed the specialized computer software used to analyze the microscopic spaces between tumor collagen fibers and to calculate their density.
The tissue fiber images were obtained using second-harmonic generation microscopy, in which a long-wavelength laser light is deflected off the collagen fibers for a few seconds, allowing for several planes and fields of view to be captured. An 880-µm wavelength was chosen because it can penetrate the tissue beyond the colorful lightwaves visible to the human eye but does not damage or heat up the cancer cells as a slightly longer infrared wavelength would.
Many of the fields of view were randomly taken throughout the tissue sample, providing a “realistic representation of each breast cancer sample,” Glunde said. Breast biopsy samples came from tissue research collections in Maryland.
The study – with funding support from the National Institutes of Health’s National Cancer Institute – appeared in the Journal of Biomedical Optics