Introduction. Axillary lymph node dissection remains one of the mainstays of breast cancer because clinical, imaging or laboratory methods are insufficient to define nodal status, the most reliable predictor of disease outcome. Sentinel lymph node biopsy is becoming standard practice in most centers.
Several radiopharmaceuticals have been used successfully in the sentinel node identification. Controversies still exist regarding the best agent to be used in this procedure.
We randomly compared Dextran500-99mTc and Phytate-99mTc in the scintigraphic detection of sentinel lymph nodes in a 2 hour interval protocol. The primary endpoint was the detection of axillary or internal mammary lymph nodes.
Methods. A total of 46 patients were enrolled in the research protocol from May 2002 until April 2004. The mean age was 56 years (ranging from 34 to 81 years).
Inclusion criteria were the histological diagnosis of early breast cancer, without previous surgical treatment. Patients with systemic disease, clinically positive axillary examination, multiple tumors and those who were pregnant were excluded. Each patient performed lymphocintigraphy two times in distinct days (at least three days interval) with different radiopharmaceuticals. Neither the physician performing tracer administration nor the patient knew what radiotracer was used. Scintigraphic images were reviewed by two nuclear medicine physicians blinded to the used tracer. Both radiotracers were administered the same way.
All tests were two tailed. A P value less than or equal to 0.05 was considered significant.
Results Eighty eight lymphoscinthigraphic studies were performed in forty four patients. In the first hour image 34 patients from Dextran500-99mTc group showed sentinel lymph nodes versus 28 positive examinations using Phytate-99mTc (P=0.113). In the second hour image using Dextran500-99mTc as the radiotracer there were 39 positive studies opposed to 30 positive examinations using Phytate-99mTc (P=0.036). Including both radiotracers, a total of sixty nine ( 78.4%) examinations were positive in the two hour interval of investigation. The number of nodes detected in each patient also had a statistically significant difference between both groups. Those who were evaluated with Dextran500-99mTc had a mean of 1.6 (1.31) lymph nodes detected by scintigraphy compared to 1 (0.92) lymph nodes detected in the Phytate-99mTc group (P=0.002).
Discussion In our institution Phytate-99mTc and Dextran500-99mTc are available for sentinel node mapping. However we didnt know the clinical implication of choosing one of them for routine use.
Both tracers that we prospectively compared had very similar particle size as described by their supplier. We found Dextran500-99mTc as being better for use in a two hour interval protocol indicating that other clinically important factors influenced their drainage from injection site.
In conclusion, 99mTc-Dextran500 is better than 99mTc-phytate for use in a two hour interval scintigraphic protocol because it demonstrates the sentinel node in a significantly higher number of patients and also showed more lymph nodes suitable for pathological examination.