Thymidine phosphorylase expression is preserved after radiotherapy in patients with cervical squamous cell carcinoma

The aim of this study was to investigate the changes in two of the enzymes involved in fluorouracil metabolism, thymidine phosphorylase (TP) and dihydropyrimidine dehydrogenase (DPD), in uterine cervical squamous cell cancer tissue after radiotherapy.

Cervical tissue from 27 patients diagnosed with stage IIIB or IV uterine cervical squamous cell cancer was compared with normal cervical tissue from 33 patients with benign gynecologic diseases. Expression of TP and DPD in the cervical tissues was measured using enzyme-linked immunosorbent assays. TP and DPD expression before and after irradiation with 10 and 20 Gy was measured in 9 of the 27 patients with cervical cancer.

Before irradiation, DPD expression in cancer tissue did not differ from that in normal tissue. TP expression and the TP/DPD ratio were significantly higher in cancer tissue than in normal tissue ( P<0.00001). TP and DPD expression and the TP/DPD ratio were not significantly changed by irradiation with 10 and 20 Gy. TP expression and the TP/DPD ratio after irradiation with 10 and 20 Gy were significantly higher than in normal tissue.

The increased TP expression and the elevated TP/DPD ratio following irradiation with up to 20 Gy may offer an increased clinical advantage to chemoradiotherapy with capecitabine or doxyfluridine over radiotherapy alone.