Elevation of plasma prolactin in patients undergoing autologous blood stem-cell transplantation for breast cancer: is its modulation a step toward posttransplant immunotherapy?

Abstract

Prolactin is a suspected promotor of breast cancer cell growth, and it shares pleiotropic immunoregulatory properties. We studied plasma prolactin and its drug-induced modulation in 20 women with breast cancer undergoing high-dose chemotherapy and autologous blood stem-cell transplantation. Plasma prolactin levels were serially assayed before and during conditioning and within and beyond 30 days after transplant. Before transplant, prolactin plasma levels were in the age-adjusted range of normal women. During conditioning and within 30 days after transplant, prolactin levels increased in all patients (p < 0.0001), but remained in the normal range. Antiemetic drugs such as metoclopramide and phenothiazines, known to enhance pituitary prolactin secretion, further elevated prolactin plasma levels (p < 0.00001). Patients remaining in continuous complete remission after transplant (median follow-up, 3 years) disclosed higher prolactin levels compared with those obtaining only partial remission or ensuing early relapse. Prolactin levels are regularly elevated during conditioning and within 30 days after autologous transplantation for breast cancer. Further elevations of prolactin plasma levels are induced by metoclopramide and other antiemetic drugs. Elevated plasma prolactin had no adverse effect on disease-free survival after transplant. We propose to investigate further the upregulation of prolactin after transplant aiming to induce a posttransplant consolidative immune reaction.