Optimal detection of micrometastases in sentinel lymph node of breast cancer: CBCSG-001 trial.

Abstract

Abstract Abstract #1011 Background: Although sentinel lymph node biopsy (SLNB) has become the method of choice for axillary staging, the extent of the pathological examination (HE or IHC, the number or intervals of sections) described in the literature differed considerably between studies, particularly for the detection of micrometastases (MMs). As one of the second objectives of the CBCSG–001 trial (China multicenter study of sentinel node biopsy substituting axillary node dissection), our aim was to evaluate the optimal methods and intervals for the detection of SLN macrometastases, MMs and isolated tumor cells (ITCs).
 Material and Methods: Two hundred and forty-five continuous breast cancer patients with 569 SLNs identified “negative” with standard HE stain carried on initial 4 levels were retrospectively analyzed. All SLNs were step sectioned (SS) at 100µm interval, and for each level both HE and IHC with AE1/AE3 were performed. Then HE and IHC detection rates were analyzed at 100-, 200-, 300-, 400-, and 500µm intervals for the detection of macrometastases, MMs and ITCs.
 Results: In 245 cases with original SLN negative cases, 36 (14.7%), 49 (20.0%) and 49 (20.0%) cases were found to had metastases with SS HE, SS IHC, and SS HE+IHC, respectively (SS IHC/ SS HE+IHC vs. SS HE, p>0.05). In all the 5741 sections, metastases were found in 180 sections (3.1%) by SS HE, 307 (5.4%) by SS IHC, and 322 (5.6%) by SS HE+IHC (p=0.000). The metastases included macrometastases 12.2%, MMs 61.2%, and ITC 26.5%. The detection rates of MMs were 7.8%, 12.2%, and 12.2%, respectively (SS IHC/ SSHE+IHC vs. SS HE, p>0.05). The detection rates of ITCs were 4.5%, 5.3%, and 5.3%, respectively (p>0.05). The detection rates of metastases were significantly higher in patients with invasive lobular carcinoma (57.1%) than with invasive ductal carcinoma (16.7%, p=0.001), but no significant differences were found among different ages, tumor sizes, locations, grades, ER, PR, and HER-2 status (all p>0.05). The detection rates of metastases at 100-, 200-, 300-, 400-, and 500-µm intervals by SS HE were 14.7%, 13.5%, 11.4%, 8.6%, and 7.8%, respectively. No significant differences were found between 100- and 200-µm intervals (p=0.697), and between 100- and 300-µm (p=0.284), while p<0.05 between 100-µm and other intervals. The detection rates of metastases at 100-, 200-, 300-, 400-, and 500-µm intervals by SS HE+IHC were 20.0%, 18.8%, 18.0%, 16.3%, and 13.1%, respectively. No significant difference was found between 100- and 200-µm intervals (p=0.732), 100- and 300-µm (p=0.565), and between 100- and 400-µm (p=0.292), while p=0.041 between 100-µm and 500-µm.
 Conclusion: SS HE could significantly increase the detection rate of SLN metastasis compared to our routine 4 levels HE pathological examination. SS HE+IHC could further improve the detection of SLN metastases. The detection rates of metastases were significantly higher in patients with invasive lobular carcinoma than those with invasive ductal carcinoma. The optimal interval for the detection of micrometastases in SLN was 300-µm with SS HE, and 400-µm with SS HE+IHC. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 1011.