Lack of predictive value of potential doubling time and iododeoxyuridine labelling index in radiotherapy of squamous cell carcinoma of the head and neck.

Purpose: To investigate the prognostic value of T(POT), S-phase time (TS), iododeoxyuridine (IdUrd) labelling index (LI) and DNA index with loco-regional tumour control as the end-point.

Materials And Methods: Iododeoxyuridine was given to 99 patients with squamous cell carcinomas of the head and neck before the start of radiotherapy. The analysis included FCM parameters (LI, TS, T[POT] and DNA index, n = 87) and LI determined by immunohistology (IHC, n = 45). A hybrid T(POT) was determined by combining the FCM TS and the IHC LI (n = 45). In diploid tumours (n = 39), the FCM LI was underestimated and the FCM T(POT) was overestimated because the flow cytometer was unable to distinguish between tumour and normal cells. The 'tumour LI' was defined as the IHC LI or the FCM LI of aneuploid tumours when a biopsy for IHC evaluation was not available and similarly the 'tumour T(POT)' was determined by the hybrid T(POT) or the FCM T(POT) of aneuploid tumours (n = 63).

Results: There was good agreement between the IHC LI and the FCM LI for aneuploid tumours, but there was disagreement for diploid tumours. The median tumour T(POT) was 4.1 days (range 0.6-19.5 days) and the median tumour LI was 12.9% (range 3.1-46.0%). In a univariate analysis there was no prediction of loco-regional tumour control by the LI, the TS or the T(POT) determined by either of the methods. T-classification, N-classification, clinical stage and tumour diameter were related with loco-regional tumour control, whereas clinical stage was the only parameter that yielded independent prognostic significance in a multivariate analysis.

Conclusions: This study does not confirm the significant prognostic value of T(POT) as indicated in some previous reports. Larger clinical studies are needed to draw final conclusions.