Relationships of DNA ploidy, S-phase fraction and hormone receptor status to tumor stage in breast cancers detected by population screening. The South-East Sweden Breast Cancer Group.

Cellular DNA content was analyzed by flow cytometry and estrogen and progesterone receptors by an immuno-biochemical method (EIA) in a consecutive series of 807 frozen breast-cancer samples. Before the beginning of the study, a mammography screening program had been introduced in the region where the tumors were diagnosed. Forty percent of the tumors were judged as DNA diploid, of which 86% were ER-positive. The proportion of ER-positive tumors among non-diploids was significantly lower, or 73% (p less than 0.001). S-phase fraction (SPF) was estimated in 691 cases (86%), with an overall mean of 8.4%. DNA ploidy as well as ER and PR status were independently related to SPF. Unlike the results obtained in most older series, the biological variables correlated significantly with tumor staging factors such as lymph-node status and tumor size. Patients with nodal involvement, especially those with 4 positive nodes or more, more often had tumors which were receptor-negative, DNA aneuploid and of high S-phase rate. Large tumor size was significantly related to lower frequencies of receptor positivity and strongly related to DNA aneuploidy and high S-phase fraction. Multiple linear regression analysis showed that these relationships were mainly due to the associations of SPF with the other variables. S-phase fraction was the only independent factor predicting nodal status, while DNA ploidy in addition to SPF was associated with tumor size. In fact, DNA ploidy (p less than 0.001), ER and PR status (p less than 0.001, p = 0.002), nodal status (p = 0.04) and tumor size (p less than 0.001) were all independently related to SPF.