Tumour proliferation assessed by combined histological and flow cytometric analysis: implications for therapy in squamous cell carcinoma in the head and neck.

The two techniques of flow cytometry analysis (FCM) and immunohistochemical localisation of bromodeoxyuridine (BrdUrd) incorporation after in vivo administration, were combined to study proliferation in squamous cell carcinoma of the head and neck region. Care was taken in this study to ensure that similar material was processed using both techniques such that comparisons could be made. FCM underestimated the labelling index (LI) in tumours classified as diploid compared to the histological evaluation of the tumour cells within those tumours (4.6% vs 17.1%). However, in aneuploid tumours, the FCM LI (10.7%) was similar to that obtained from histology (13.5%). Indeed, proliferation assessed by the combination of histology LI and FCM duration of S-phase (Ts) indicated that diploid tumours had a shorter median potential doubling time (Tpot) of 2.1 days compared to aneuploid (2.8 days). Despite the heterogeneity of proliferation evident histologically within the specimens, there was not a wide variation in the results of FCM analysis when multiple samples from resections were studied. Using FCM data alone, 46% of the tumours showed a Tpot of less than 5 days. When the Ts from the FCM data was combined with the average histological LI, 84% were less than 5 days and with the maximum LI, 99% were within this time interval. Compared with previous estimates, the proportion of tumours possessing proliferative characteristics which may indicate the need for acceleration of treatment seems to be much larger.