Mc. Gorisse et al., ESTIMATION OF POTENTIAL DOUBLING TIME (TP OT) IN-VIVO, BY FLOW-CYTOMETRY - PRACTICAL PROBLEMS AND POSSIBLE SOLUTIONS, Bulletin du cancer, 83(10), 1996, pp. 825-834
Kinetic parameters of tumour growth yield predictive values and allow
an optimisation of the treatment schedule, especially for fractionatio
n in radiotherapy. Among those parameters, the labelling index (LI) an
d the potential doubling lime (Tpot) may be measured by flow cytometry
, a semi-quantitative analysis, after in vivo administration bf iodode
oxyuridine (IdUrd) to humans. This Begg's recommended methodology need
s the selection of thresholds and gates whose boundaries are arbitrary
. They can be positioned on a more objective basis using a negative co
ntrol (aspecific fixation). Moreover a previous identification of the
different cell populations of the tumour samples according to the meth
od of Vindelov allows a better determination of these cell populations
processing IdUrd-DNA staining. This procedure was used with 11 tumour
biopsies including mainly head and neck cancers. This method displaye
d results similar to the literature concerning LI and Tpot determinati
ons as well as shortened Tpot when the patients recurred. One sample h
as no labelling at all. A small function, likewise up to 10% of cells
exhibiting an S DNA content were not labelled by IdUrd. These cells le
ave the S phase or progress too slowly in order to display IdUrd uptak
e. Intra-tumoral hypoxia is a possible explanation of these findings.
DNA ploidy and the percentage of cells in S phase could be worth while
to precise the relationship between DNA index and tumour kinetic. The
measurement of Tpot could also be used in other cancers and for optim
isation of dose of chemotherapy.