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A fluorescence-guided imaging system could improve intraoperative detection of residual breast cancer in women undergoing lumpectomy, a prospective single-arm study suggested.

The system, which incorporates the activatable fluorescent imaging agent pegulicianine (LUM015) had higher sensitivity, though lower specificity, than standard pathology review of the main lumpectomy specimen, reported Shelley Hwang, MD, MPH, of Duke University in Durham, North Carolina.

Incorporating the pegulicianine fluorescence-guided surgery (pFGS) system reduced the need for re-excision in 19% of patients undergoing standard breast conserving surgery, according to findings presented at the annual meeting.

"If all surgeons had adhered to the protocol and excised all lumpectomy cavity areas with signal, the pFGS system could potentially have reduced the need for re-excision by up to 32%," said Hwang.

"It is very difficult sometimes to clear lumpectomy margins in patients undergoing breast conserving surgery," said Hwang. "It can be challenging because ducts can branch into irregular patterns, tumor growth can be unpredictable and extend past the mammographic abnormality, and microscopic disease can be difficult to appreciate intraoperatively."

As a result, she noted, 10% to 40% of patients need a second or sometimes even a third surgery to clear positive margins.

The study was conducted across 16 U.S. sites and enrolled 234 adult women with newly diagnosed primary invasive breast cancer or ductal carcinoma in situ. Patients were injected intravenously with pegulicianine prior to surgery at a dose of 1.0 mg/kg. After tumor excision per standard of care, pFGS was used to identify and remove residual cancer.

The main outcomes and measures were performance, re-excision rates, and adverse events.

In assessing the performance of pFGS, Hwang and her colleagues found that pFGS prompted additional margin excisions in 138 patients, with residual tumor found in 26 (19%).

Negative margins after standard of care breast conserving surgery were achieved in 192 of 230 (83.5%) patients. But pFGS-guided excision in 14 of those 192 turned up residual tumor, meaning cancer tissue would have otherwise remained in those 14 women.

As for the correlation of pFGS with routine pathology assessment of the main lumpectomy specimen, "when we compared the pFGS signal to the assessment of the initial lumpectomy, the sensitivity of the pFGS system is much higher than the pathological evaluation of the lumpectomy," Hwang pointed out.

The pFGS system had a sensitivity of 69.4% (95% CI 56.3-80.4) compared with 38.2% (95% CI 27.2-50.0) with the standard pathology assessment of the lumpectomy. Meanwhile, specificity was 70.4% (95% CI 68.1-72.7) and 91.2% (95% CI 88.3-93.5), respectively.

The negative predictive value was 98.2% (95% CI 97.3-98.9) for pFGS versus 90.5% (95% CI 87.5-92.9) for standard pathology assessment.

While the study showed pFGS was safe, with a low rate of adverse events, the one patient with a history of allergy to contrast agents had an anaphylactic reaction, but subsequently recovered.

These findings, "including a notably high negative predictive value," support further clinical assessment of pFGS, which is currently being conducted in a , Hwang reported.

During a discussion period, Hwang was asked whether pFGS could be used to identify cancer in the lymph nodes.

"Theoretically it should be able to," Hwang said. "And we have thought about this a little bit in different areas of breast cancer where this potentially could be valuable. One setting is in patients who completed neoadjuvant therapy, so we are testing that right now."

She noted this study was designed to look at tumor that was right at the lumpectomy edge. "If you had a large fatty node I think it would be more difficult to detect a signal," Hwang said. "We haven't done enough work yet to know whether it might be valuable in those settings."

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