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SPECT imaging evaluation of 111indium-chelated cetuximab for diagnosing EGFR-positive tumor in an HCT-15-induced colorectal xenograft

2017.02.08.

Bin-Bin Shih et al, Journal of the Chinese Medical Association, 2017

Summary

Colorectal cancer (CRC) occurs with high incidence worldwide, but is usually diagnosed in late stage with metastasis by the conventional methods. Epidermal growth factor receptor (EGFR) is overexpressed in 97% of CRC cells, serving a promising diagnostic candidate. In the present study, Cetuximab, an anti-EGFR monoclonal antibody was conjugated with an isotope chelator, diethylene triamine penta acetic acid (DTPA), labeled with 111indium (111In) and injected to tumor bearing mice. Biological distrubution was investigated by SPECT/CT imaging.

Results revealed that 111In-Cetuximab accumulated in the both small (50mm3) and large (250mm3) tumors, whereas the ratio of tumor to muscle in the large tumor was 7.5-fold. The biodistribution data indicated that the 111In-cetuximab bound to tumor specifically that was higher than that in other organs. Consequently, 111In-cetuximab is suggested to be suitable for early diagnosis and prognostic monitor of EGFR-positive CRC in further clinical practice.

Results from nanoSPECT/CT

  • The tumor of the 111In-Cetuximab group was apparently observed both in 24h and 48h and higher than that in the 111In group.
  • 111In-Cetuximab majorly accumulated in liver and tumor, otherwise, 111In accumulated only in the kidney.
  • The tumor to muscle ratio of 111In-Cetuximab was measured 7.5-fold, which was higher than that of 111In group measured as 3.1-fold, indicating that 111In-cetuximab specifically bound to EGFR-positive tumors as a reliable diagnosing agent.
  • The result also indicated that 111In labeled with Cetuximab through chelator DTPA was easily excreted out the mice better than free 111In, suggesting that this labeling method may not lead to accumulation of 111In metal in mice.

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