The Lynx Group

Occult Metastases Do Not Warrant Axillary Dissection in Breast Cancer

October 2011, Vol 2, No 6

San Francisco, CA—The debate over the clinical significance of occult micrometastases in the lymph nodes of patients with breast cancer continues.

NSABP B-32 Trial: No Effect on Overall Survival

Investigators from the National Surgical Adjuvant Breast and Bowel Project (NSABP) B-32 trial have reported very small but significant differences in outcomes for patients with occult metastases. However, in a follow- up analysis, they reported that survival is not improved if these patients undergo full lymph node dissection.

Thomas B. Julian, MD, Allegheny General Hospital, Pittsburgh, PA, reported the study results at the 2011 Breast Cancer Symposium.

Previous investigators found a 1.2% improvement in survival and a 2.8% improvement in disease-free survival (DFS) among patients lacking occult metastases; however, overall survival (OS) at 5 years was excellent in both groups: 94.6% with occult metastases and 95.8% without.

“So our question was, if there is a difference according to the presence of occult metastases, did the addition of axillary dissection factor into this?” Dr Julian said. “We found no effect of treatment on OS and DFS.”

In the subanalysis, nearly 16% of clinically node-negative patients were found to have occult metastases on more detailed assessment of the sentinel nodes. Among the 3986 patients with clinically and hematoxylin and eosin–negative sentinel nodes, occult metastases were identified in 616 patients: 316 in the axillary lymph node dissection (ALND) arm and 300 in the sentinel node dissection (SND) arm (for 51 per arm, occult metastases status remained unknown).

The clinical outcomes of the patients were similar, whether they underwent SND or ALND, Dr Julian reported. “The clinical importance of immunohistochemistry- detected occult metastases is questionable,” he said.

Among patients with occult nodal metastases, complete ALND did not significantly improve OS (hazard ratio [HR], 0.89; P = .62) or DFS (HR, 0.79; P = .16). The actual differences in outcomes were less than 3%.

Similar Findings in ACOSOG Z0011

The results support previous findings from the American College of Surgeons Oncology Group (ACOSOG) Z0011 study, which found no survival benefit from complete ALND compared with SND only. In Z0011, more extensive dissection revealed that 27% of patients had positive nodes beyond the sentinel nodes, said Armando E. Giuliano, MD, of Cedars-Sinai Medical Center, Los Angeles, who was the principal investigator of Z0011.

“About 27% of patients with SNDonly had unresected cancer remaining in the axilla,” he noted. “We as surgeons affect survival by achieving local-regional control, and both approaches did that. There was no difference in survival.”

Taken together, the 2 studies— NSABP B-32 and ACOSOG Z0011— suggest that aggressive approaches to surgically remove occult metastases are not necessary.

Diminishing Returns, Increased Expense

Donald L. Weaver, MD, University of Vermont College of Medicine, Burlington, who served as the NSABP B-32 protocol pathologist, agreed that the 2 studies have important implications; namely, they argue against intensively looking for small metastases that will not make a difference in outcome.

“The more you look, the more you find,” Dr Weaver acknowledged, but this results in diminishing returns and additional work and is of questionable value to the patient, he suggested. “Occult metastases are not discriminatory predictors of outcome.”

“If additional treatment was given based exclusively on the presence of occult metastases, 90% of these patients would be overtreated,” he said. Dr Weaver calculated that this amounts to $44.8 million in healthcare dollars spent annually to account for a 1.2% difference in outcome. His recommendation is that pathologists should continue to examine 2- mm sections, one from each block, without requiring levels or immunohistochemistry.

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