LACK OF PROGNOSTIC-SIGNIFICANCE OF THE MONOCLONAL-ANTIBODY KI-S1, A NOVEL MARKER OF PROLIFERATIVE ACTIVITY, IN NODE-NEGATIVE BREAST-CARCINOMA

In a series of 205 node-negative breast cancers (NNBC), we determined staining by the novel antibody Ki-S1, a marker of tumor cell prolifera tion, in order to test its association with other prognostic variables and its prognostic significance. Ki-S1 was determined in routinely fo rmalin-fixed paraffin-embedded tumor samples. Ki-S1 gave a nuclear sta ining in the majority of the carcinomas (188 of 205), with percentages of reacting nuclei ranging from 2% to 90% (median value of 7%). In 10 7 tumors frozen sections were available to also assess the Ki-67 antib ody. Among these, 94 had a nuclear staining of cancer cells ranging fr om 5% to 80% (median value of 7%). In 46 tumors we also determined the MIB-1 antibody. The percentage of MIB-1 nuclear staining ranged from 1% to 50% (median value of 20%). There was no significant relationship between Ki-S1 and the other two cell kinetic markers. Ki-S1 labeling was significantly associated only with tumor size (p = 0.03). With a m edian follow-up of 6 years, Ki-S1 had no significant prognostic value for either relapse-free survival (RFS) or overall survival (OS)(Ki-S1 as continuous logarithmic variable; p = 0.86 and p = 0.23, respectivel y). For RFS the following variables had a significant prognostic value : Ki-67 (less than or equal to 10% vs > 10%;p = 0.037); progesterone r eceptor (PgR) expression (- vs +/++; p = 0.041); tumor size (pn vs pT2 -3; p = 0.042) and grading (GI vs GII-III; p = 0.047). For OS, tumor s ize (p = 0.0044), age (continuous variable; p = 0.0060), and Ki-67 (p = 0.043) were significantly prognostic. In multivariate analysis (fina l model), only tumor size retained a significant and independent progn ostic value for RFS (p = 0.0042). For OS, both tumor size (p = 0.0029) and age (less than or equal to 55 years vs > 55 years; p = 0.041) ret ained significance in the multivariate model. In conclusion, Ki-S1 doe s not seem to have prognostic relevance in this series of NNBC. Possib le hypotheses to explain this observation are discussed.