Feature: Small breast lesions can be diagnosed with NIR optical tomography
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| An ultrasound image of a suspicious lesion in the left breast in 76-year-old study participant (Zhu et al). Image Source: Radiology |
Diffuse optical tomography in the NIR region is an emerging modality that can provide functional quantification of tumor hemoglobin concentration (tHb), which is directly related to tumor angiogenesis and tumor hypoxia, lead study author Quing Zhu, PhD, a professor of bioengineering at the University of Connecticut in Storrs, Conn., said in an interview. Researchers sought to investigate the potential role of this technology with ultrasonographic localization as a means of differentiating early-stage cancers from benign lesions in the breast.
However, “[optical tomography] is not an independent modality and this technology can tell the likelihood based on modalities, such as ultrasound, along with the chances are of a lesion being malignant or benign,” explained Zhu. “The two diagnostic tools have really good synergy together.”
The HIPAA-compliant study recruited 178 consecutive women with an average age of 52 years from the University of Connecticut Health Center from September 2004 to September 2008 and from Hartford Hospital in Hartford, Conn. from September 2007 to September 2008.
The participants underwent ultrasound-guided biopsy to indicate solid masses or lesions. The participants were then imaged with a handheld probe consisting of a coregistered ultrasound transducer and an NIR imager, guided by the lesion locations sited by the initial ultrasound.
All core biopsy and surgical specimens were initially reviewed by two attending pathologists blinded to the optical imaging results.
They measured light absorption from the optical imaging at two different wavelengths (780 and 830 nanometers) and evaluated tumor angiogenesis on the basis of calculated total hemoglobin concentration (tHb) and correlated this measurement with the core biopsy results. In addition, the authors acquired optical data from the normal contralateral breast to be used as reference for calculating the background optical absorption. The tHb was correlated with pathologic parameters within the patients diagnosed with carcinomas and followed up with subsequent excision, the researchers wrote.
Within their patient cohort, Zhu and colleagues observed two cases of in situ carcinomas (Tis), 35 T1 carcinomas, 24 T2–T4 carcinomas and 114 benign lesions. The mean maximum and mean average tHb of the Tis–T1 group were 102.0 m mol/L and 71.9 m mol/L and those of the T2–T4 group were 100.3 m mol/L and 67.0 m mol/L respectively. The mean maximum and mean average tHb of the benign group were 55.1 m mol/L and 39.1 m mol/L, respectively.
From this data, the authors determined that a two-fold higher tHb was found in malignant invasive breast cancer lesions when compared to benign lesions after the employment of optical tomography.
Moreover, Tis-T1 cancers resulted in 92 percent sensitivity, 93 percent specificity, 81 percent positive predictive value and 97 percent negative predictive value. For T2-T4 tumors, sensitivity, specificity, positive predictive value and negative predictive values were determined to be 75, 93, 69 and 95 percent, respectively.
“We found the new technology is suited for the diagnosis of the small lesions, and this is good news because small lesions are the lesions that physicians and radiologists are having trouble identifying, and they are harder to biopsy because the needle has to be accurate to pinpoint the location,” explained Zhu.
Despite the findings pointing to the technology being especially helpful for smaller lesions, Zhu noted that the study also found that optical tomography can play a role in the detection of larger lesions. “We think that for larger lesions, technology can add more information to what was found by ultrasound, including tHb distribution features, like heterogeneous peripheral enhancement or posterior shadowing,” she said.
The technology can result in cost-saving opportunities as well, noted Zhu, explaining that with optical tomography as a second or third modality, radiologists may determine that some patients may not require biopsies and instead be good candidates for watchful waiting for six months. In addition, the technology may help radiologists improve diagnostic confidence.
Down the road, “we envision that this technology will be very valuable to image patients who are very highly suspicious for early stage invasive breast cancers. We would like the adjunct technology to translate to clinical application, but this needs another level of a multiple-site clinical study," Zhu concluded.