Breast cancer survival and immunohistochemical similarities between primary and metastatic sites, as a surrogate marker for the cancer self-seeding.

We have tested 6 immunohistochemical (IHC) parameters (ER, PgR, Ki-67, bcl-2, p53 and cathepsin D) on a group of 60 patients with ductal invasive breast cancer, in both primary tumors and their axillary lymph node metastasis and determined whether there were statistically significant differences between the 2 sites. The data collected on IHC features of breast cancers and their axillary metastasis were compared with the Wilcoxon matched-pairs test and resulted in 1 p-value for each patient. The multivariate Cox proportional hazard model was applied on the overall survival data of our 60 breast cancer patients to test the significance of the listed 6 IHC features found in primary tumors and in positive lymph nodes. Besides, the patients were divided in 3 subgroups according to the distribution of their IHC similarity and a Kaplan-Meier analysis was performed to compare these groups. Our results suggest that self-seeding is detectable by the statistical comparison of the IHC features in 2 tumor sites. Two things seem important in all this: in our patients IHC similarity was a continuous variable and was related to survival.