DNA PLOIDY OF PRIMARY BREAST-CANCER AND LOCAL RECURRENCE AFTER BREAST-CONSERVING THERAPY

The value of DNA-flow cytometry and clinico-pathological prognostic factors for the prediction of local recurrences after breast-conserving therapy (BCT) were evaluated in a retrospective study. Thirty-one patients with a local recurrence were compared with 31 matched patients without a local recurrence. Morphology and DNA-indices of the local recurrences and their corresponding primary tumours were compared. Ductal carcinoma in situ was present significantly more often in the group with a primary recurring tumour, than in the matched group (P < 0.001), and the same holds for lobular carcinoma (n = 5). Half of the tumours that recurred had macroscopically positive surgical margins compared to about one-fourth of the matched group. Fifty-six per cent of the DNA-aneuploid stemlines in cases with local recurrence were present in the corresponding primary tumour as well (confidence limits 45%-75%), an indication that the majority of local recurrences are true recurrences and not independently developed tumours. The lack of similarity of DNA stemlines between some primary DNA-aneuploid tumours and their local recurrence indicates that these tumours had developed independently. The percentage of DNA-aneuploid cases in the group with local recurrence (89%) did not differ significantly from that in the matched group (70%). However, the findings suggest a selective recurrence of DNA-diploid stemlines. This might indicate increased resistance of DNA-diploid tumour cells to radiotherapy as compared with the resistance level in DNA-aneuploid cells.