Effect of Chemotherapy on Somatostatin Receptor Detection with Octreotide Scintigraphy in Hormone-refractory Prostate Cancer Patients

Background: Neuroendocrine cells have been found in all stages of prostate cancer. Neuroendocrine differentiation of prostate adenocarcinoma is a possible target for therapeutic strategies, such as administration of GH analogs (e.g., somatostatin), especially in patients with hormone-refractory prostate cancer (HRPC). The presence of receptors for these drugs in tumor cells and tissues is essential and is assessed with 111 In-octreotide scintigraphy (Octreoscan). The relationship between these receptors and chemotherapy, the new standard therapy for HRPC, is unknown. Patients and Methods: 111 In-octreotide scintigraphy was performed on 20 patients affected by HRPC, all with metastatic disease. Chemotherapy with a single agent was also administered to all patients. Results: In 63% of the patients, all metastases were negative to Octreoscan. Several metastases were positive in 37% of patients only, compared to 94% previously described in a chemotherapy-naive population. Conclusion: Chemotherapy seemed to reduce the cellular receptors for somatostatin analogs.