Proliferation indices of invasive breast carcinomas after in vivo 5-bromo-2'-deoxyuridine labelling: a flow cytometric study of 75 tumours.

In vivo labelling of human breast tumours with 5-bromo-2'-deoxyuridine and analysis of proliferation by multiparameter flow cytometry is a new tool by which the labelling index, S phase duration (TS) and potential doubling time (Tpot) of the tumour can be estimated. Tumour specimens from 75 patients with invasive breast carcinoma were studied. Six tumours could not be analysed, and the TS and Tpot values could not be calculated for a further 18. The median labelling index (n = 69) was 4.2 per cent. The median TS (n = 51) was 8.7 h and the median Tpot (n = 51) was 8.2 days. The median intra-assay coefficient of variation for determination of the labelling index was 0.29 in five tumours. There were no significant differences in the total labelling index, TS or Tpot when patients were stratified according to lymph node status, tumour size, tumour grade or menopausal status.