Flow cytometry in primary breast cancer: improving the prognostic value of the fraction of cells in the S-phase by optimal categorisation of cut-off levels

Abstract

Summary The use of continuous prognostic variables is clinically impractical, and arbitrarily chosen cut-off points can result in a loss of prognostic information. Here we report findings from a study of primary breast cancer, showing how the prognostic value of the fraction of cells in the S-phase of the cell cycle (SPF), as measured by flow cytometry, can be affected by the SPF cut-off level(s) adopted. It was possible to evaluate the SPF in 566 (94%) of 603 consecutive cases where fresh frozen specimens were available in a tumour bank at our department. Clinically, all patients were without distant spread at the time of diagnosis, and the median duration of follow-up was 4 years. Using different survival end-points and x2 values for each cut-off level, two optimal cut-off points, at the 7% and 12% levels, were consistently obtained for the SPF. The aim of the current study was to elicit optimal cut-off levels for the SPF in primary breast cancer, as determined with FCM.Correspondence: H. Sigurdsson. Received 3 January 1990; and in revised form 9 July 1990. Patients and methodsIn the health care region of southern Sweden hormone receptor analyses are routinely performed on specimens from patients with primary breast cancer, any residual tumour specimens being stored in a tumour bank at the Oncology Department at University Hospital in Lund.The study included 603 consecutive cases where specimens were available in the tumour bank, and which fulfilled the following inclusion criteria: (1) tumour sample from primary breast cancer (cancer in situ excluded); (2) diagnosed during the period between September 1982 and January 1986; (3) clinically without signs of distant metastasis at the time of diagnosis; (4) sufficient tumour specimen to yield a DNA histogram; and (5) tumour cells microscopically identified in a cytopathologic investigation of all imprints used for making cell suspensions for DNA analysis.The median age of the patient population was 63 years (range 26-97). Tumour size was taken from the pathological report and usually determined on a unfixed specimen. A median of ten axillary lymph nodes was investigated. The distribution of cases by tumour size was as follows: 0-20mm, n=250 (41%); 21-50mm, n=317 (53%); and > 51 mm, n = 36 (6%). Distribution by axillary lymph node status was: node-negative, n = 303 (50%); node-positive, n = 277 (46%); and no axillary staging performed, n = 23 (4%).Laboratory methods Tumour samples were taken from biopsies originally obtained for steroid receptor analysis. Fresh specimens from the macroscopic mammary tumours were taken by the examining pathologist, except in a few cases where it was done during surgery. The specimens were stored frozen (-70°C), and later analysed (in a single laboratory) at the Oncology Department in Lund. Flow

One or multiple samplings for flow cytometric DNA analyses in breast cancer‐prognostic implications?

“…SPF in the two samples manifested significant positive correlation (r, = 0.76; p < 0.001). Previous results obtained at our department have demonstrated that dividing a breast cancer series into three SPF categories (SPF < 7.0%; 7.0 5 SPF < 12% and SPF 2 12%), gave SPF the strongest prognostic value (36). In the present work, we have therefore used the same division into three SPF groups when studying the variation in SPF between the two samples from the same breast cancer specimen.…”

Optimizing flow cytometric DNA ploidy and S‐phase fraction as independent prognostic markers for node‐negative breast cancer specimens

“…Another approach has been to ignore this diploid dilutional effect and use raw S-phase, DS for DNA diploids and AS for DNA aneuploids, as a single prognostic variable (26,63). This method works very well because the DNA ploidy information is essentially embedded in the S-phase and they are both inversely correlated to relapse.…”

Preoperative Fine Needle Aspiration from Human Breast Cancer is a Valuable Sampling Material for Progesterone Receptor and Cytometric Dna Analysis

“…For clinical purposes, however, cut-off levels are often adopted to define low and high SPF subgroups. At our laboratory, diploid tumours with an SPF value >,7.0% and non-diploid tumours with an SPF value >, 12 are classified as having high SPF, and the remainder as having low SPF (33). If these cut-off levels are applied in the present series, the concordance in SPF categories between F N A and biopsy materials would only be obtained in 68% (28/41) of cases overall, in 79% ( 1 1/14) of cases of diploid tumours, and 64% (14/22) of cases of nondiploid turnours.…”