INTRINSIC RADIOSENSITIVITY AND PREDICTION OF PATIENT RESPONSE TO RADIOTHERAPY FOR CARCINOMA OF THE CERVIX

The intrinsic radiosensitivity of cervical carcinoma has been measured using a soft agar clonogenic assay. All patients received radical rad iotherapy alone with a minimum of 2 years post-treatment follow-up. On ly women with stage I, II and III disease were included in the analysi s. Values for cell surviving fraction at 2 Gy (SF2) were obtained for 88 tumours with an assay success rate of 73%. The 53 patients alive an d well at the time of analysis had tumours with a mean SF2 that was si gnificantly lower than the value from the 22 patients with locoregiona l failure (P< 0.01). Patients with radioresistant tumours (SF2 > 0.40, the median) had a significantly lower 3 year survival level than thos e with sensitive tumours (SF2 less-than-or-equal-to 0.40) (P = 0.002). Also the frequency of local recurrence was higher (P = 0.001) whether these were central (P = 0.009) or peripheral (P = 0.046). Cell surviv ing fraction at 3.5 Gy was obtained for 46 tumours and the 3 year pati ent survival rate was significantly higher for those with SF3.5 values less than the median (P = 0.043). There was, however, no difference i n the level of local recurrence (P = 0.24). The ability to grow in cul ture was not associated with significantly poorer patient survival (P = 0. 56) or failure to control the primary disease (P = 0. 17). While high colony forming efficiencies were associated with an increased rat e of local recurrence (P = 0.029) they did not predict for overall pat ient survival (P = 0.32). These data suggest that, for cervical carcin oma treated with radical radiotherapy, intrinsic radiosensitivity is i mportant in determining treatment outcome.