Measurements of dynamic tumour cell kinetic parameters, particularly t
he potential doubling time (T-pot), may have potential as predictive a
ssays for treatment outcome after radiotherapy. This paper details the
distributions of T-pot and other kinetic and DNA content parameters m
easured in rectal cancers. Biopsies were taken from 119 patients appro
ximately 6 h after infusion of 200 mg m(-2) bromodeoxyuridine (BrdUrd)
. The samples were analysed by bivariate DNA/BrdUrd flow cytometry. Th
e primary purpose of the study was to measure the kinetic parameters o
f labelling index (LI), duration of S-phase (T-s) and T-pot. Secondari
ly, tumour DNA ploidy (DNA index) and S-phase fractions (SPFs) were al
so estimated from the univariate DNA histograms. The 101 evaluable pat
ients were classified according to clinical stage as T2 (n = 12), T3 (
n = 53), T4 (n = 28) or recurrent tumours (n = 8). Of the evaluable tu
mours, 73 were DNA aneuploid. The median LI, T-s, and T-pot of the ane
uploid tumours were 21%, 20 h and 3.3 days respectively. The calculate
d LI, T-s, and T-pot of diploid rumours were subject to uncertainties
because of the contribution of normal cells. The LI and SPF of all tum
ours were, however, significantly (P < 0.001) correlated, having a cor
relation coefficient of only 0.76. The wide distributions of values fo
r LI (quartiles 13.5%, 26.9%) and T-pot (quartiles 2.4, 5.6 days) that
were found are necessary baseline information if these parameters are
to be useful in individual treatment selection or as predictors of tr
eatment outcome.