Sentinel lymph node biopsy for breast cancer: from investigational procedure to standard practice

Dual-isotope lymphoscintigraphy using albumin nanocolloid differentially labeled with 111In and 99mTc

The aim of this study was to develop and evaluate 111In- and 99mTc-labeled derivatives of albumin nanocolloid (NC) for dual-label lymphoscintigraphy to allow simultaneous comparison of lymphatic flow from different tissue planes draining a tumour bed for accurate identification of sentinel lymph nodes (SLN). Using the chelator, p-isothiocyanatobenzyl-1,4,7, 10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA), 111In-DOTA-NC and 99mTc-DOTA-NC were compared in vitro with respect to stability of labeling, colloidal status and particle size, then in vivo by measuring their clearance rates from a subcutaneous injection depot. 111In-DOTA-NC and 99mTc-DOTA-NC were indistinguishable on the basis of in vitro criteria. Their in vivo clearance rates, however, were disparate (0.0015 to 0.075 min(-1) for 111In and 0.0072 to 0.067 min(-1) for 99mTc), 111In being faster in three studies and markedly slower in three. This demonstrates that even when dual-labeled radiotracers behave identically in vitro, they will not necessarily do so in vivo. Further work is needed to develop dual-labeled NC.

Axillary lymph node metastases in patients with breast carcinomas: assessment with nonenhanced versus uspio-enhanced MR imaging

PURPOSE

To prospectively assess the accuracy of nonenhanced versus ultrasmall superparamagnetic iron oxide (USPIO)-enhanced magnetic resonance (MR) imaging for depiction of axillary lymph node metastases in patients with breast carcinoma, with histopathologic findings as reference standard.

MATERIALS AND METHODS

The study was approved by the university ethics committee; written informed consent was obtained. Twenty-two women (mean age, 60 years; range, 40-79 years) with breast carcinomas underwent nonenhanced and USPIO-enhanced (2.6 mg of iron per kilogram of body weight intravenously administered) transverse T1-weighted and transverse and sagittal T2-weighted and T2*-weighted MR imaging in adducted and elevated arm positions. Two experienced radiologists, blinded to the histopathologic findings, analyzed images of axillary lymph nodes with regard to size, morphologic features, and USPIO uptake. A third independent radiologist served as a tiebreaker if consensus between two readers could not be reached. Visual and quantitative analyses of MR images were performed. Sensitivity, specificity, and accuracy values were calculated. To assess the effect of USPIO after administration, signal-to-noise ratio (SNR) changes were statistically analyzed with repeated-measurements analysis of variance (mixed model) for MR sequences.

RESULTS

At nonenhanced MR imaging, of 133 lymph nodes, six were rated as true-positive, 99 as true-negative, 23 as false-positive, and five as false-negative. At USPIO-enhanced MR imaging, 11 lymph nodes were rated as true-positive, 120 as true-negative, two as false-positive, and none as false-negative. In two metastatic lymph nodes in two patients with more than one metastatic lymph node, a consensus was not reached. USPIO-enhanced MR imaging revealed a node-by-node sensitivity, specificity, and accuracy of 100%, 98%, and 98%, respectively. At USPIO-enhanced MR imaging, no metastatic lymph nodes were missed on a patient-by-patient basis. Significant interactions indicating differences in the decrease of SNR values for metastatic and nonmetastatic lymph nodes were found for all sequences (P < .001 to P = .022).

CONCLUSION

USPIO-enhanced MR imaging appears valuable for assessment of axillary lymph node metastases in patients with breast carcinomas and is superior to nonenhanced MR imaging.