In contrast, a long-term (median of 67 months observation) prospective clinical study found that PTHrP expression in primary breast tumors correlated with a reduction in bone metastases and an overall better prognosis, while patients with primary tumors that were PTHrP-negative were more likely to develop-PTHrP-positive bone metastasis and an overall worse prognosis [24]. This evidence concerns the gene PTHLH and metastasis.