Sister chromatid exchange in lymphocytes from patients with malignant lymphoma

Sister chromatid exchange (SCE) frequencies were studied in differentially stained lymphocytes from 47 patients with malignant lymphoma. Thirteen patients were untreated when studied. The mean SCE frequency [+/- standard error (SE)] for these patients was 12.7 +/- 0.9 per mitosis. The mean score for 40 controls was 6.1 +/- 0.3. SCE mean scores were significantly higher in the untreated patients than in the controls (P less than 0.001). Seven patients were treated with radiotherapy alone. They demonstrated a mean SCE frequency (8.8 +/- 0.8) significantly lower (P less than 0.01) than that found in untreated patients. Eleven patients received cyclophosphamide within 4 weeks prior to study. They demonstrated a mean SCE frequency (14.3 +/- 1.3) significantly higher (P less than 0.05) than that found in patients who had received regimens that did not contain cyclophosphamide in the prior 4 weeks (11.1 +/- 1.3) or who had been off drugs for at least 8 weeks (10.1 +/- 0.8). Our data suggest that untreated patients with malignant lymphoma have elevated SCE frequencies, which may be further increased by certain chemotherapeutic agents.