Radionuclide imaging of HER2/neu expression in metastatic axillary lymph nodes in breast cancer patients: comparing the efficacy of [99mTc]Tc-ADAPT6 and [99mTc]Tc-(HE)3-G3

Aim . To conduct a direct comparative analysis of single-photon emission computed tomography (SPECT-CT) with [ 99m Tc]Tc-ADAPT6 and [ 99m Tc]Tc-(HE) 3 -G3 in patients with HER2-positive breast cancer (BC) with axillary lymph node metastases. Materials and methods . The analysis included 8 patients with HER2-positive BC with axillary lymph node metastases before the systemic treatment. All patients were injected with [ 99m Tc]Tc-ADAPT6 (500 µg) and [ 99m Tc] Tc-(HE) 3 -G3 (3,000 µg) with an interval of 3–4 days. The SPECT-CT scans of the chest and upper abdomen were performed after 2 hours for [ 99m Tc]Tc-ADAPT6 and after 4 hours for [ 99m Tc]Tc-(HE) 3 -G3. The accumulation of radiopharmaceuticals was assessed by measuring the maximum standardized uptake values (SUV max ) in metastatic axillary lymph nodes, projections of the contralateral axillary lymph nodes, liver, latissimus dorsi muscle, and spleen. Additionally, mALN-to-background and mALN-to-reference organs ratios were calculated for each patient. Results . Comparison of the mALN-to-background ratio revealed the advantage of [ 99m Tc]Tc-ADAPT6 (38.93 (16.56–56.02)) over [ 99m Tc]Tc-(HE) 3 -G3 (19.39 (8.43–34.52)), p = 0.0391. The comparative analysis of the accumulation of the studied radiopharmaceuticals in the reference organs demonstrated higher SUV max for [ 99m Tc] Tc-(HE) 3 -G3 in the liver and spleen (4.44 (2.85–9.08) and 2.47 (1.28–4.41), respectively) than for [ 99m Tc]Tc-ADAPT6 (2.98 (1.96–3.65) and 0.43 (0.14–0.62), respectively), p = 0.01 and p = 0.04. Comparison of the SUV max ratios in mALN and reference organs showed higher values of mALN / spleen for [ 99m Tc]Tc-ADAPT6 (5.93 (1.04–11.85)) compared to [ 99m Tc]Tc-(HE) 3 -G3 (1.83 (0.46–4.54)), p = 0.02. Conclusion. According to the results of the performed analysis, the diagnostic advantage of [ 99m Tc]Tc-ADEPT6 for the detection of) HER2/neu expression in metastatic lymph nodes in breast cancer patients was revealed.