When Sentinel Lymph Node Biopsy is Enough in Breast Cancer

Nick Mulcahy

May 19, 2009

May 19, 2009 — It's a common dilemma for clinicians and their patients with breast cancer: whether or not to perform completion axillary dissection after nodal metastases have been identified by sentinel lymph node biopsy (SLNB).

A new observational study of 22,278 women suggests that the answer is frequently no, especially if the nodal metastases are microscopic. The study was published online April 13 in the Journal of Clinical Oncology.

A full axillary dissection may not be necessary for most patients.

"A full axillary dissection may not be necessary for most patients," senior study author David J. Winchester, MD, told Medscape Oncology. Dr. Winchester is chief of the Division of General Surgery and Surgical Oncology at NorthShore University HealthSystem in Evanston, Illinois.

He explained that, in the study, completion axillary lymph node dissection (ALND) did not improve outcomes in either axillary recurrence or survival for patients with microscopic disease. Furthermore, there may only be a small benefit with regard to those outcomes with completion ALND for those with macroscopic disease, he suggested.

In patients with macroscopic nodal metastases, axillary recurrence and survival were comparable between the 2 treatment groups.

However, after the analysis was adjusted for differences between the 2 groups, there was a nonsignificant trend toward better outcomes for completion ALND than for SLNB alone — hazard ratio for axillary recurrence was 0.58 (95% confidence interval [CI], 0.32 - 1.06) and for overall survival was 0.89 (95% CI, 0.76 - 1.04), Dr. Winchester and colleagues report.

Still, the study results should cause clinicians to not automatically use completion ALND, noted Dr. Winchester.

We have relied upon that operation too much.

"We have relied upon that operation too much, and this paper points out that we may not need to do it in terms of a survival difference or a regional recurrence difference. This is an operation associated with significant morbidity," he said in a statement.

For instance, the risk for edema is 30% to 40% with completion ALND, and 2% to 5% with SLNB, he said.

The need for completion ALND has been debated for some time, and led to theAmerican College of Surgeons Oncology Group (ACOSOG) Z0011 trial comparing the 2 approaches, say the study authors. However, the trial was suspended after 5 years, in 2004, due to low patient accrual.

An ad hoc analysis of ACOSOG Z0011 showed that 69% of node-positive patients who refused to enroll went on to undergo completion ALND, Dr. Winchester and coauthors comment. They also say if there is ever another prospective clinical trial comparing the 2 approaches, then the current study's results could provide some "equipoise" for random assignment to SNLB alone.

Shift in Practice

Dr. Winchester and colleagues used data obtained from the National Cancer Data Base on women with clinically node-negative breast cancer who underwent SLNB and who had nodal metastases from 1998 to 2005 (n = 97,314).

In addition to evaluating outcomes in these women, the investigators of the new study tallied the proportion of patients undergoing SLNB and completion ALND.

The results indicate that there has been a shift in practice patterns concerning the procedures.

"For microscopic nodal disease from 1998 to 2005, the proportion of patients undergoing [SLNB] alone without a completion nodal dissection increased considerably, from about 25% to 45%, whereas for patients with more substantial nodal metastases (the macroscopic group), the proportion stayed fairly constant over the time course of the study," said study lead author Karl Bilimoria, MD, MS, in a statement. He was an American College of Surgeons Research Fellow at the time the analysis was performed, and is now a surgical resident at the Feinberg School of Medicine of Northwestern University in Evanston, Illinois.

Specifically, the proportion of patients who underwent SLNB alone for macroscopic disease declined during the study period, from 24.2% to 16.7%; (< .001); however, the proportion of patients who underwent SLNB alone for microscopic metastases increased, from 24.7% to 45.3% (< .001).

Dr. Bilimoria speculated that the increase in the use of SNLB alone for microscopic disease arose as physicians "anecdotally found that nodal dissection is not necessary in all patients."

Outcomes Data in Further Detail

Because there was a limited number of women with 5-year follow-up in the database, the outcomes analysis comprised a smaller group of women (n = 22,278) and was limited to the years 1998 to 2000. The group had a median follow-up of 63 months.

In patients with microscopic nodal metastases (n = 2203), there was not a significant difference in outcomes between SLNB alone (5 or fewer nodes) and SLNB with completion ALND (9 or more nodes) — either unadjusted or adjusted for differences in clinico-pathologic characteristics, treatment, and hospital type.

In patients with macroscopic nodal metastases (n = 20,075), on univariate analysis, there was not a significant difference in outcomes between SLNB alone and SLNB with completion ALND (1.0% vs1.2% [P = .40] for axillary recurrence, 98.5% vs98.2% [= .72] for relative survival, and 82.1% vs81.8% [= .55] for observed survival).

However, as noted above, after the analysis was adjusted for differences in clinico-pathologic characteristics, treatment, and hospital type, there was a nonsignificant trend toward worse outcomes with SLNB alone than with SLNB with completion ALND for macroscopic disease.

The study was supported by the American College of Surgeons Clinical Scholars in Residence program and the Department of Surgery, Feinberg School of Medicine, Northwestern University.

J Clin Oncol. Published online before print April, 13 2009. Abstract

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