A water-soluble porphyrin, 5,10,15,20-tetrakis[3,4-bis(carboxymethyleneoxy)phenyl] porphyrin (T3,4BCPP), was successfully labeled with 99m Tc and biodistribution studies were performed in Wistar rats. Scintiimaging and in vivo distribution studies were also carried out in C 6 -gliomas and mammary tumor-bearing animals using a gamma camera. Tumor-to-muscle (T/M) ratios were calculated and compared with those obtained with the known tumor-seeking radiopharmaceuticals 99m Tc(V)-DMSA (DMSA = dimercaptosuccinic acid), 99m Tccitrate and 201 TlCl. In the case of C 6 -gliomas, the ratios were 4.2, 2.2, 4.00 and 3.0; while in the case of C 3 H/J mammary tumor, the ratios were 9.4, 8.8, 8.1 and 8.5 for T3,4BCPP, 99m Tc(V)-DMSA, 99m Tc-citrate and 201 TlCl, respectively. Similar studies were carried out in N-methyl-N-nitrosourea (NMU)-induced mammary tumor animals and the T/M ratios obtained were 5.9, 2.0, 5.3 and 3.3 for T3,4BCPP, 99m Tc(V)-DMSA, 99m Tc-citrate and 201 TlCl, respectively. The radiolabeled photosensitizer could perhaps be used to detect cancer non-invasively and could even prove useful in monitoring the progression/regression of tumors before, during, and after chemotherapy, radiation therapy or photodynamic therapy (PDT).
