Review
Sentinel lymph node biopsy in patients with microinvasive breast cancer: A systematic review and meta-analysis

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Abstract

Background

The aim of this meta-analysis is to evaluate the role of sentinel lymph node biopsy (SLNB) in patients with microinvasive breast cancer.

Methods

We searched MEDLINE and ISI Web of Science to identify studies including patients with microinvasive breast cancer who underwent SLNB and reported the rate of sentinel-node positivity. We performed proportion meta-analysis using either fixed or random-effects model based on the between-study heterogeneity.

Findings

A total of 24 studies including 968 patients met the eligibility criteria. The summary estimate for the sentinel-node (SN) positivity rate was 3.2% (95% Confidence Interval (CI): 2.1%–4.6%), 4.0% (95% CI 2.7%–5.5%), and 2.9% (95% CI: 1.6%–4.6%) for macrometastasis, micrometastasis and isolated tumor cells (ITC) respectively. Significant between-study heterogeneity was observed only in the meta-analysis of ITC positivity rate.

Interpretation

The amount of positive sentinel node in patients with proven microinvasive breast cancer is relatively low. As a result, the indications for SLNB in these patients should be probably individualized.

Introduction

Microinvasive breast cancer comprises a subset of T1 breast cancer in which the focus of invasion is no larger than 1 mm in size.1 These foci of invasive cells are usually observed in the background of ductal carcinoma in situ (DCIS).2, 3

By definition, DCIS is preinvasive and does not have the potential to spread to regional lymph nodes. In the pre-sentinel lymph node biopsy (SLNB) era, axillary dissection in patients with DCIS was not recommended due to the high morbidity of the procedure and the questionable clinical benefit.4 In this new era of SLNB, where the method has become the standard of care in the staging of breast cancer due to the considerably lower morbidity than axillary dissection,5, 6 SLNB can be recommended in patients with DCIS in the preoperative biopsy in certain circumstances. For instance, SLNB can be recommended when a mastectomy is indicated, as axillary staging by SLNB is essentially impossible if an invasive tumor is found with examination of surgical specimens.7

SLNB is also recommended if microinvasion is found on final pathology.7 However, the evidence for this recommendation is considered insufficient because the studies that underlies the recommendation are mostly retrospective with small sample size.8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31

The purpose of this meta-analysis is to gather all available evidence and evaluate the role of SLNB in patients with microinvasive breast cancer.

Section snippets

Search strategy

We conducted a comprehensive systematic electronic search through MEDLINE and ISI Web of Knowledge, without year or language restriction, by using the following searching algorithm: (microinvasive OR occult) AND (breast OR mammary) AND (cancer OR carcinoma OR tumor OR malign*) AND (sentinel OR sentinel node biopsy OR SLNB). The last search was updated on April 2013.

We also conducted secondary referencing by manually reviewing reference lists of potentially eligible articles. Additionally, the

Eligible studies

A total of 225 abstracts were identified with the search criteria; of these, 42 full-text articles were reviewed as potentially eligible and 24 met the inclusion criteria (Fig. 1).

Fifteen studies9, 12, 13, 15, 16, 17, 19, 20, 23, 24, 25, 26, 28, 29, 31 were retrospective, 78, 10, 11, 18, 21, 22, 27 were retrospective with retrieval of data from a prospectively collected database while two14, 30 was prospective. The number of patients with microinvasive breast cancer included in the eligible

Discussion

This meta-analysis of nearly 1000 patients with microinvasive breast cancer who underwent SLNB showed that the SLN-positivity rate for macrometastasis in those patients was low (3.2%). Even in the worst-case scenario, based on the 95% confidence interval, the positivity rate remained acceptably low, namely 5.6%. Similar low positivity rates were observed for micrometastases or ITC.

Microinvasive breast cancer is mainly observed after postoperative pathologic analysis in the setting of DCIS. The

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