Protein synthesis rate measured with L-[1-C-11]tyrosine positron emission tomography correlates with mitotic activity and MIB-1 antibody-detected proliferation in human soft tissue sarcomas

Protein synthesis rate (PSR can be assessed in vivo using positron emission tomography with L-[1-C-11]tyrosine (TYR-PET). Biological activity of soft tissue sarcomas (STS) can be measured in vitro by the mitotic rate and numb er of proliferating cells. In STS the grade of malignancy, in which the mit otic index plays a major role, is considered to be the major standard in pr edicting biological tumour behaviour. This study was designed to test the v alidity of TYR-PET in relation to different histopathological features. In 21 patients with untreated STS, the PSR was measured using TYR-PET. The num ber of mitoses was counted and rumours were graded according to the grading system of Coindre et al. ((Cancer 1986; 58:306-309). Proliferative activit y was assessed by immunohistological detection of the Ki-67 nuclear antigen using MIB-1 monoclonal antibody. To test the association between the PSR a nd these tumour parameters, a correlation analysis was performed. A signifi cant (P<0.05) correlation was found between PSR and the Ki-67 proliferation index (R = 0.54), and between PSR and mitotic rate (R = 0.64). There was n o con elation between PSR and tumour grade. The present study in malignant soft tissue tumours relates in vivo tumour metabolism as established with T YR-PET to tumour activity measured in vitro and indicates that the non-inva sive method of TYR-PET can estimate the mitotic and proliferative activity in STS.