Introducing Optical Spectroscopy: A New Cancer Detection Method

While the debate continues as to whether mammography impacts breast cancer survival rates, one fact looms large. The need persists for better imaging options that can detect breast disease at its very earliest stage, irrespective of breast density, patient's tumor and its size—imaging options that inarguably impact patient survival.

Any new technology would best serve patients if it conferred no radiation or other toxicities and was compression and pain free. Achieve this at a reasonable cost and low error rate and you can really increase women's confidence in breast cancer detection methods. You get down to the bottom line: saving lives and sparing breasts!

In an attempt to address current limitations in breast cancer screening, the State of California Breast Cancer Research Program granted funding to an investigator with a non-invasive, non-toxic, and highly innovative potential solution to this need. The approach presents a new algorithm for looking at breast changes in a high-tech yet patient-friendly way.

Scientist and Associate Professor Dr. Bruce J. Tromberg, Director of the Laser Microbeam and Medical Program at UC Irvine's Beckman Laser Institute, has developed a handheld laser-based scanner that can detect subtle physiological changes in breast tissue—changes that possibly indicate the beginning of breast cancer. The laser breast scanner uses a technique known as “frequency domain diffuse optical spectroscopy.” This optical technique specifically detects changes in water, fat, and hemoglobin (iron-containing center of red blood cells) concentration that can signal alterations in tissue. It is highly sensitive to subtle changes, such as cellular growth and proliferation of the blood vessels surrounding a tumor.

“This scanner yielded quantitative information about changes in breast tissue that cannot be obtained with noninvasive techniques like mammography, MRI [magnetic resonance imaging], or ultrasound,” Tromberg said. “Because we can obtain precise information about changes in the way the components of breast tissue function, we hope to be able to detect precancerous and cancerous conditions earlier, especially in younger women, whose breast tissue can be too dense for mammography. Women who have gone through menopause and are receiving hormone replacement therapy also can have dense breast tissue and may benefit from the scanning technique.”

The question of mammography's usefulness extends beyond its ability to detect tumors in young women or menopausal women on hormone replacement therapy (HRT). It can fail to detect (a) tumors in high-density breast tissue, irrespective of age and hormone use, (b) lobular carcinomas, and (c) highly aggressive "interval" cancers. Additional concerns are the danger of radiation exposure on young breast tissue, addressed in a growing body of literature, and the difficulty of identifying women with BRCA1 mutations and AT heterozygotes, which can require repeated screenings just to become obvious to the radiologist. The detection device of the future must address these shortcomings.

In his efforts to create a new detection method, Dr. Tromberg focuses on examining the consumption of oxygen by tumors versus healthy cells and the recruitment of blood vessels around breast lesions (angiogenesis). He is also looking at the transition of postmenopausal breast tissue from collagen to fat and the breakdown of cells in the extra-cellular matrix-how breast cancer cells invade healthy tissue. His approach is to analyze the entire breast, looking for global changes that are characteristic of breast disease.

In one study, Dr. Tromberg and his colleagues scanned breast tissue from 28 volunteers (ages 18 through 64), measuring how fat, water, and hemoglobin changed as women aged. The handheld unit-slightly larger than an ultrasound device-was able to determine the components of breast tissue regardless of its density or the woman's age, hormone levels, and menopausal status. It might also prove valuable in determining which patients are at high risk of recurrence post treatment, for monitoring the impact of chemotherapy on breast tissue, and for measuring the efficacy of chemoprevention strategies.

His work now includes measurements of locally advanced tumors with the goal of determining how individuals respond to presurgical, neoadjuvant chemotherapy. In addition, patients are recruited from the STAR Trial to determine the effects of chemoprevention drugs like tamoxifen and raloxifene on breast tissue. Women interested in participating in this research can contact Montana Watna, at (949) 824-9265 or Donna Jackson at (714) 456-8549.

Of course it isn't enough to visualize or characterize the changes occurring in the body. They must be quantified for medical and research purposes. Dr. Tromberg and his team are investigating and comparing units of measurement with the best utility.

While this form of optical spectroscopy isn't ready for prime time yet, going forward it has the potential to become a powerful diagnostic tool that could both detect initial cancer and determine which patients are at high risk of recurrence after treatment. Optical spectroscopy might also be used to monitor the impact of chemotherapy on breast tissue and to measure the effectiveness of chemoprevention strategies such as giving drugs like tamoxifen to high-risk healthy women.

The grant from the California BCRP has enabled Dr. Tromberg to build another scanner for use at University of California, San Francisco. He seeks to increase the number of sites that will conduct the research so that more women can be enrolled in these studies. At $75,000 the equipment is much more reasonable than any of the currently used methods, and it is designed for convenient use as a bedside device. From this advocate's optical perspective, it's all looking good. There's one more bonus: it makes one feel as if watching all those Star Trek episodes was time constructively spent!!

CBCRP Award

Dr. Tromberg received a $50,000 IDEA award from CBCRP in 1996 to begin developing the optical density scanner and a $500,000 Translation Collaboration Research award in 2000 to refine the scanner and bring it into the clinic.