Prostate cancer treated by radiotherapy

According to respective proportions of evolutive status groups, results of multivariate studies are difficult to interpret. Among the 1099 cases of local form of prostate cancer, treated by radiotherapy from 1975-1982 in 16 French Anticancer Institutes, we can observe two homogeneous status groups of patients: disease-free survivors (285 cases) and patients who died of prostate cancer (278 cases, 51%). Among other things, they are comparable in size, for age at beginning of radiotherapy and for delay between histologic diagnostic and radiotherapy. It was chosen to analyse them using multivariate analysis. To take survival into account, a Cox model and Kaplan-Meier curves were used; the group deceased of prostate cancer was further analyzed by a tree-structured regression method. The Cox model and the Kaplan-Meier curves confirmed two main explicative factors: Stage (p < 0.0001) and tumor grade (p < 0.001). Poorer evolution occurs in extracapsular forms and grade I has better survival than others. The tree-structured regression method indicates 2 other pejorative factors: hormonotherapy prior to radiotherapy and presence of cardiovascular pathology. Though the pelvic dose does not appear to be a main explicative factor, it seems to improve survival and delay between radiotherapy and recurrence or metastasis in some categories of cases. Other factors such as tumor dose, age and delay between diagnosis and radiotherapy were not found to be significant. These results cannot be extended to the whole population for which they do not constitute a predictive study. They are considered as 'baseline data'. In further studies, other evolving status groups will be situated in reference to the above results, and prostate cancer evolution will be studied by taking into account all evolving status groups according to their respective proportions and characteristics. (author). 15 refs., 8 figs