['Several reports have shown that cells with p53 mutations display increased resistance to ionizing radiation, a treatment often used clinically for localized prostate carcinoma.', 'Totals of 18 post-irradiated locally recurrent prostatic carcinoma specimens and 25 (no radiation) stage D1 node-positive (TxN+MO) primary prostatic carcinoma specimens were tested for p53 immunoreactivity by immunohistochemistry. Of the 18 post-radiation locally recurrent prostatic carcinomas 10 were further analyzed by single strand conformational polymorphism to assess the validity of using this immunohistochemistry approach in irradiated tissue for detecting p53 alterations. Specimens showing p53 alterations by single strand conformational polymorphism were subjected to nucleotide sequence analysis or tested for loss of heterozygosity at a locus within the p53 gene.', 'Of the 25 stage TxN+MO prostatic carcinomas without radiation 5 (20%) were immunoreactive (consistent with the reported incidence of positive immunoreactivity in clinical/surgical stage TxN+MO primary prostatic carcinomas). In contrast, 13 of 18 post-radiation locally recurrent prostatic carcinoma specimens (72%) were immunoreactive. Multivariate logistic regression analysis showed no dependence of p53 immunoreactivity to grade, stage or androgen status in the post-radiation locally recurrent prostatic carcinoma group, while 8 of 10 hormone naive prostatic carcinoma specimens (80%) were immunoreactive. The temporal relationship between p53 alterations and radiotherapy was assessed. Pre-irradiation prostatic carcinomas available from 5 patients with immunoreactive post-radiation locally recurrent disease were analyzed and all were immunoreactive.'] Are p53 immunohistochemical and genetic alterations associated at high incidence with post-irradiated locally persistent prostate carcinoma?