The ratio of maximum percent tumour accumulations of the pretargeting agent and the radiolabelled effector is independent of tumour size

UMMS Affiliation

Department of Radiology, Division of Nuclear Medicine

Publication Date


Document Type



Animals; Antibodies, Neoplasm; Antineoplastic Agents; Colonic Neoplasms; Disease Models, Animal; Dose-Response Relationship, Immunologic; Indium Radioisotopes; Male; Mice; Mice, Nude; Morpholines; Morpholinos; Neoplasm Transplantation; Radiopharmaceuticals; Technetium Compounds; Tissue Distribution


Neoplasms | Oncology | Radiology


Our previous studies have indicated that the optimal dosage ratio of pretargeting antibody to effector is proportional to their maximum percent tumour accumulations (MPTAs). This study quantitatively describes how both MPTAs and their ratio change with tumour size, to simplify pretargeting optimisation when tumour size varies. The CC49 antibody dosages below saturation of the tumour antigen level were first examined for the LS174T tumour mouse model. Then the MPTAs of the antibody in mice bearing tumours of different sizes were determined, always at antibody dosages below antigen saturation. Historical data from this laboratory were used to collect the MPTAs of the (99m)Tc-cMORF effector for different tumour sizes, always at effector dosages below that required to saturate the MORF in tumour. The MPTAs versus tumour sizes for both the antibody and the effector were fitted non-linearly. The best fit of the antibody MPTA (Y(antibody) with tumour size (x) in grams was Y(antibody)=19.00 x(-0.65) while that for the effector was Y(effector)=4.51x(-0.66). Thus, even though the MPTAs of both vary with tumour size, the ratio (Yantibody/Yeffector) is a constant at 4.21. In conclusion, the MPTA ratio of the antibody to the effector was found to be constant with tumour size, an observation that will simplify pretargeting optimisation because remeasurement of the optimum dosage ratio for different tumour sizes can be avoided. Theoretical considerations also suggest that this relationship may be universal for alternative antibody/effector pairs and for different target models, but this must be experimentally confirmed.


Tumour accumulation, Tumour size, Pretargeting, Effector, Optimisation

DOI of Published Version



Eur J Cancer. 2009 Nov;45(17):3098-103. doi: 10.1016/j.ejca.2009.09.007. Link to article on publisher's site

Journal/Book/Conference Title

European journal of cancer (Oxford, England : 1990)

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PubMed ID