Synthesis of trans-1,2-cyclohexyldinitrilo tetramethylene phosphonic acid and its radiolabelling with 99mTc for the detection of skeletal metastases.
OBJECTIVE
The development of bone-seeking radiopharmaceuticals for the detection of malignant bone lesions could further improve the diagnostic accuracy of routine bone scanning. This study aimed to provide a convenient synthesis of trans-1,2-cyclohexylenedinitrilo tetramethylene phosphonic acid (CDTMP) and an improved preparation of its (99m)Tc complex.


METHODS
CDTMP was prepared from trans-1,2-cyclohexyldinitrilotetraacetic acid by reaction with phosphorus trichloride and it was labelled with (99m)Tc. Toxicity and biodistribution studies were carried out in BALB/c mice, while blood clearance and bone scintigraphy studies were carried out in rabbits. (99m)Tc-CDTMP was evaluated for the detection of malignant bone lesions in 11 patients. Bone scintigraphy (a methylene diphosphonate scan) was performed to detect metastases at diagnosis and follow-up.


RESULTS
The radiolabelling efficiency was found to be >97% and the stability in serum indicated that (99m)Tc remained bound to the chelate, CDTMP, for up to 24 h. Blood clearance showed a quick wash-out from the circulation and the biological half-lives (t12) were 55 min (F) and 8 h 48 min (S). The LD50 was 110 mg.kg(-1) as determined by toxicity studies. The drug was excreted mainly through renal route and the accumulation of (99m)Tc-CDTMP in bone was 7.69+/-0.65%ID/g at 1 h. The mean ratio of bone lesion to soft tissue was 6.8+/-0.69 and of bone lesion to normal bone was 5.67+/-0.82. Visual image analysis of (99m)Tc-CDTMP was clinically comparable to the interpretation of imaging studies with (99m)Tc-MDP.


CONCLUSIONS
These preliminary data support increased bone uptake by the tetraphosphonate complex of (99m)Tc. This suggests that CDTMP complexed with therapeutic radionuclides should be evaluated for therapy of skeletal metastases.
Panwar
Puja
P
Institute of Nuclear Medicine and Allied Sciences, Delhi, India.
Chuttani
Krishna
K
Mishra
Pushpa
P
Sharma
Rajnish
R
Mondal
Anupam
A
Kumar Mishra
Anil
A
D000818:Animals; D001859:Bone Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism / Q000556:secondary*; D006801:Humans; D007553:Isotope Labeling / Q000379:methods; D008297:Male; D008657:Metabolic Clearance Rate; D051379:Mice; D008807:Mice, Inbred BALB C; D009928:Organ Specificity; D063065:Organophosphonates / Q000737:chemistry / Q000493:pharmacokinetics*; D011817:Rabbits; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000138:chemical synthesis / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013667:Technetium / Q000737:chemistry / Q000493:pharmacokinetics*; D014018:Tissue Distribution
C514232:1,2-cyclohexylenedinitrilo tetramethylene phosphonic acid; D063065:Organophosphonates; D019275:Radiopharmaceuticals; D013667:Technetium