Sensitivity of Intraoperative Frozen Section for SLN Biopsy

NEW ORLEANS—Pathologic examination of an intraoperative frozen section of the sentinel lymph node (SLN) is less sensitive for breast cancer patients with smaller tumors and/or micrometa-static disease. In a recent study, use of routine frozen section avoided reoperation in only 4% of patients with T1a cancers, but was more useful in other stages, reported Martin R. Weiser, MD, of Memorial Sloan-Kettering Cancer Center.

Pathologic examination of a biopsied sentinel lymph node during surgery may avoid a second operation if the results are positive. But this report indicated the method is not accurate for all patients.

At the Society of Surgical Oncology Cancer Symposium, Dr. Weiser presented the results of a large Memorial Sloan-Kettering study.

Sentinel lymph node biopsy and intraoperative frozen section analysis were performed in 890 of 1,000 consecutive patients with invasive breast cancer. The results were matched against the outcomes of enhanced pathologic analysis with serial sections of nonfrozen samples from the same patients.

The study found that 231 patients (26%) had SLN metastases, and 58% of these were diagnosed with intraoperative frozen section analysis. But the sensitivity of the frozen section was related to the size of the metastatic deposit.

The method yielded good results with SLN macrometastases (greater than 2 mm), finding 92%. But it did not perform well in the case of micrometastases (2 mm or smaller), correctly identifying only 23% of these. The difference by lesion size was significant (P < .001), Dr. Weiser reported.

“If we look at just those patients with macrometastatic SLN deposits, we see that the sensitivity of intraoperative frozen section is quite high in all categories and is, in fact, independent of the tumor stage. And if we look at only those patients with micrometastatic SLN deposits, we see that the sensitivity of frozen section is low in all groups and is also independent of primary tumor stage,” he said.

As patients move from stage T1a to T2, the proportion of patients with mac-rometastatic disease increases, and this is paralleled by an increase also in frozen section sensitivity (Table). Patients with T1a tumors mostly had micrometastatic deposits that were missed by frozen section, whereas patients with T2 disease mostly had macrometastatic deposits that were picked up by frozen section, he said.

Indications for Frozen Section

Dr. Weiser said, “Routine sentinel node frozen section is indicated in all patients with T2 breast cancers, since 38% of these patients would avoid a reoperation for completion of axillary dissection. But in patients with T1a lesions, frozen sections may not be indicated, since only 4% will benefit from the avoidance of reoperation,” he said.

Patients with T1b or T1c lesions have a 10% to 16% benefit for avoidance of reoperation, and further cost-benefit analysis is warranted in this group, he said. “Ultimately, the benefit is relative and should be determined by the expectation of the patient and the surgeon, who will have to determine the acceptable rate of reoperation,” he said.

Commented Michael J. Edwards, MD, professor of surgery, University of Louisville (Kentucky), “This study tells us that if you have smaller tumors, the frozen section is less likely to be sensitive. The only question then becomes what to do with this information.”

Dr. Edwards departed slightly from Dr. Weiser’s position on the T1a category of patients. “I would say that frozen sections don’t cost the patient much besides money. You are identifying 4 out of 100 women who don’t have to return to the operating room for these small T1a lesions, which seems logical from a cost analysis standpoint,” he said.