Deposit detection: Spectroscopy against breast cancer

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  • Published: Jan 7, 2013
  • Author: David Bradley
  • Channels: Raman
thumbnail image: Deposit detection: Spectroscopy against breast cancer

Microcalcification, the name of the game

Tiny calcium deposits can be a telltale sign of breast cancer. However, in the majority of cases these microcalcifications signal a benign condition. A new diagnostic procedure developed at MIT and Case Western Reserve University (CWRU) could help doctors more accurately distinguish between cancerous and noncancerous cases.  Credit: Researchers

Minute deposits of calcium in breast tissue act as a marker for breast cancer. Diffuse reflectance spectroscopy has now been used to show how deposits in benign conditions can be distinguished from those present in the early stages of the disease.

Microcalcification in breast tissue can be a sign of malignancy, but more often than not they are simply a residue of a benign condition. Now, researchers at Massachusetts Institute of Technology and Case Western Reserve University have turned to diffuse reflectance spectroscopy to help them develop a clinical approach that might help doctors distinguish between cancerous and noncancerous incidence of such deposits.

Mammography often reveals microcalcification causing concern for patients and requiring an invasive biopsy to test the tissue for malignancy. However obtaining tissue from the specific region containing the deposit is difficult and in 15 to 25 percent of cases impossible. This means an inconclusive test and requires follow-up with more invasive surgery.

Diffuse detection

The MIT and CWRU team suggests that diffuse reflectance spectroscopy could help oncologists pinpoint the microcalcifications within breast tissue during the biopsy procedure and so significantly boost the success rate in obtaining a definitive diagnosis. Microcalcifications occur when calcium ions precipitate out of the bloodstream and form deposits on degraded proteins and fat molecules coincident with injured or dying cells.

Writing in the Proceedings of the National Academy of Sciences at the end of 2012, the team reports a spectroscopic success rate of 97% in their assessment and suggests that spectroscopy could be readily integrated into the current medical biopsy procedure.

Lead authors Ishan Barman, Jaqueline Soares and Narahara Chari Dingari of MIT worked on the research under Maryann Fitzmaurice of CWRU and MIT's Ramachandra Rao Dasari. "We introduce a new approach based on diffuse reflectance spectroscopy for detection of microcalcifications that focuses on variations in optical absorption stemming from the calcified clusters and the associated cross-linking molecules," the researchers say. "Our findings suggest that the substantive advantages of diffuse reflectance spectroscopy in terms of acquisition time and simple instrumentation will enable its ready translation to clinical practice, optimizing the diagnostic value of the initial biopsy and thereby reducing the number of repeat biopsies currently required."

Only about 10 percent of women with microcalcifications detecting during mammography will get a diagnosis of breast cancer. This means that follow-up biopsy is essential in ambiguous cases to avoid unnecessary surgery and treatment and conversely to ensure that those women with the disease are treated urgently. The current approach to biopsy involves obtaining X-rays from three angles and inserting a needle to obtain five to ten samples from as close to the calcium deposit as possible. Failure to obtain a sample containing microcalcifications at this stage rarely leads to success on subsequent attempts.

There won't be a next time...

"If they don't get them on the first pass, they usually don't get them at all, Fitzmaurice explains."It can become a very long and arduous procedure for the patient, with a lot of extra X-ray exposure, and in the end they still don't get what they're after, in one out of five patients."

The MIT and CWRU researchers have tried to develop a spectroscopic technique that would overcome this problem and allow the radiologist to home in on the microcalcification more precisely. Raman spectroscopy, which uses light to measure energy shifts in molecular vibrations, can reveal the necessary information about the chemical composition of the suspect tissue, but is expensive. Building on what they have learned about investigating breast tissue, the team has now shown how diffuse reflectance spectroscopy could give results just as accurate as Raman in a few seconds. This would allow the radiologist to move the needle if it is not in exactly the right spot and so get a useful sample.

The researchers tested the approach successfully on 203 tissue samples from 23 patients seeing changes in light absorption due to altered levels of specific proteins (elastin, desmosine and isodesmosine) often associated with calcium cross-links in diseased tissue.

" Currently, this method is being developed for clinical translation, where the primary focus is on fabricating a high-throughput fibre optic probe that could be inserted into the central channel of the hollow core biopsy needle," Barman told SpectroscopyNOW. "The final goal is to have the spectroscopic information provide real-time guidance of the biopsy procedure."

Related Links

Proc Natl Acad Sci, 2012, online: "Diagnostic power of diffuse reflectance spectroscopy for targeted detection of breast lesions with microcalcifications"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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