DNA cytometry in postirradiation cervical-vaginal smears

Benign radiation change (BRC) in cervical-vaginal smears may be difficult to distinguish from postirradiation dysplasia (PRD) or recurrent cervical carcinoma. The utility of DNA analysis in postirradiation smears was evaluated retrospectively in 71 patients. Representative Papanicolaou smears were restained with a Feulgen method and 100 to 250 cells were analyzed for DNA content using the CAS 200 image analysis system. Thirty-three control irradiated patients had negative smears with a minimum 3-year follow-up. Thirty controls (91%) had diploid histograms with a mean coefficient of variation of 8.2% and an average of 6.8% of cells in S and G2/M phase. Three control patients had atypical nondiagnostic histograms. Twenty-three patients had abnormal smears and subsequent local recurrence; 21 (91%) had abnormal histograms, with seven showing polyploidy and 14 showing aneuploidy. The remaining 15 patients had abnormal smears diagnosed as PRD but no evidence of recurrent carcinoma. Five were polyploid, six were aneuploid, one was diploid, and three were atypical but nondiagnostic. Interactive DNA cytometry is useful in differentiating BRC from PRD and recurrent cancer. Aneuploidy is rarely, if ever, seen in negative smears with BRC. However, BRC may be associated with broad diploid peaks and increased proliferating cells. An abnormal histogram can be seen with PRD and does not always correlate with recurrent disease.