[Detection of disseminated carcinoma cells in bone marrow and peripheral blood in primary breast cancer with RT/PCR of parathyroid hormone-related protein (PTHrP)].

The analysis of tissue specific gene expression by reverse transcription based RT/PCR methods is currently evaluated as a method for the detection of tumor cell dissemination in patients with cancer. Breast cancer tissues express PTHrP and the level of PTHrP expression in the primary tumor correlates with the incidence of metastases in the bone. We applied a RT/PCR assay of PTHrP to detect tumor cells in the mononuclear cell fraction of peripheral blood (pb) and bone marrow (bm) of patients with newly diagnosed breast cancer. PTHrP positivity was found in 18/67 pb and 20/71 bm samples. In a median follow up of 23 months there were 7 metastatic relapses (4 osseous, 2 hepatic, 1 pulmonary) and 9 local relapses in patients with primary lymph node positive breast cancer. The hepatic and pulmonary relapses had been both PTHrP-PCR negative in pb and in bm. Of the 4 patients with metastatic relapses to the bone the samples of bm had been initially negative in all cases, the pb had been positive in 2 cases. Of the 9 patients with local recurrences the pb alone had been positive in 4 patients, 5 patients had been negative in both the pb and the bm. During the period of observation there was no local and metastatic relapse detectable in the group of patients with primary lymph node negative breast cancer. In summary the increased risk for local or systemic relapse would have been predictable by RT/PCR of PTHrP alone in pb in 4 of the 9 local and in 2 of the 7 early metastatic relapses. Further follow-up of the patient cohort analysed is needed to assess the value of the RT/PCR of PTHrP as a prognostic and predictive marker in patients with breast cancer.