[Preliminary study on a new sentinel lymphoscintigraphy agent 99mTc-Rituximab for breast patient]

To develop a new imaging agent, (99m)Tc-Rituximab, for sentinel lymphoscinti-graphy and investigate its feasibility in detecting the sentinel lymph node (SLN) for breast cancer patient.

(99m)Tc-Rituximab was prepared by introducing (99m)Tc directly into the mclecule of Rituximab, thus a new kind of lymphoscintigraphy agent ((99m)Tc-Rituximab) was produced. Five Bal b/c mice and ten breast cancer patients underwent dynamic SLN mapping procedures using (99m)Tc-Rituximab. Axillary lymph node status in breast cancer patients were evaluated with the fusion images, which was processed by computer software. With ROI technique, SLN/background ratio and the rate of SLN uptake were calculated and the dynamic curve of SLN uptake was drawn. The other 61 breast carcinoma patients underwent routine lymphatic mapping. Sentinel lymph node biopsy (SLNB) and axillary lymph node dissection (ALND) were both performed in all 71 patients. Fresh SLNs and all axillary nodes were sent for pathological examination using hematoxylin and eosin (H&E) staining.

(99m)Tc-Rituximab, with a yield of about 95.0%, can show SLN status in both mice and patients. The fusion image showed SLNs clearly, even the depth of SLNs in the axilla. The results of dynamic SLN mapping showed visible SLN starting from 10 min, up to 16 h after injecting tracer, however, secondary lymph nodes were not detectable at all. In mice, the ratio of SLN/background was 2.1, the rate of uptake was about 3.0% to 3.5%, and the equation of the curve was produced as: y = 0.036x + 2.7875, r(2) = 0.9787. For breast cancer patients, the uptake rate was different from case to case, but the cure seemed to be consistent with logarithm. The result of SLNB and ALND showed that the sensitivity and accuracy of SLNB was both 100.0%. The average number of SLNs found in each case was 2.6. Of nineteen breast cancer patients (26.8%) with lymph node metastasis, 11 were found to only have SLN metastasis.

(99m)Tc-Rituximab, as a new tracer to mapping sentinel lymph node for breast cancer patient, is able to show the status of sentinel lymph node reliably. The fusing image is easy to obtain and be interpreted by the clinician.