Clinical and immunological characteristics of patients with serologic progression of prostate cancer achieving long-term disease control with granulocyte-macrophage colony-stimulating factor

Purpose: We describe the clinical and immunological characteristics of patients with biochemically relapsed prostate cancer who achieved long-term disease control with GM-CSF (Leukineo). Materials and Methods: A total of 30 patients with prostate cancer and nonmetastatic recurrent disease, as manifested by increasing PSA between 0.4 and 6.0 ng/ml after prior definitive therapy, were enrolled in a phase 11 trial. Patients received 250 mu g/m(2) GM-CSF daily subcutaneously on days 1 through 14 of a 28-day cycle until PSA or objective progression. The patient and disease characteristics of patients who remained without evidence of disease progression beyond 4 years were examined. Additionally, flow cytometry was performed in peripheral blood to characterize monocyte and dendritic cells. Results: Seven of 29 evaluable patients (24%) remained free of disease progression at a median of 5.1 years (range 4.5 to 5.6 or greater) from the start of GM-CSF therapy. Patients on long-term GM-CSF tended to have lower initial T stage, Gleason score and pretreatment PSA. An increase in the number of circulating monocytes and dendritic cells was observed after 14 days of GM-CSF treatment. These values returned to baseline during the 14-day off period. Conclusions: GM-CSF modulates PSA in androgen dependent, biochemically relapsed cases. A substantial proportion of patients achieve long-term disease control. The clinical characteristics described may help select patients for future clinical trials with GM-CSF or other immunomodulators. Additional investigation is required to define the immunological mechanism of GM-CSF in prostate cancer.