Cancer of the Prostate Presenting With Diffuse Osteolytic Metastatic Bone Lesions

A Case Report

Innocent Lule Segamwenge; Nuru Kaddu Mgori; Safia AbdallahYussuf; Celia Nantume Mukulu; Philip Nakangombe; Paul Kioko Ngalyuka; Fred Kidaaga

Disclosures

J Med Case Reports. 2012;6(425) 

In This Article

Discussion

Prostate cancer frequently metastasizes to bone with up to 90% of patients with advanced disease having bone involvement.[8,9] Bone metastases contribute significantly to the morbidity associated with advanced cancer of the prostate such as bone pain, immobility, pathological fractures, hypercalcemia, hematological disorders and spinal cord compression.[10] It has been shown that prostate cancer metastasizes to the spine before involvement of other organs.[8] Our patient had bone metastases as the initial presentation of disease with severe bone pains, hypercalcemia and hematological complications of anemia and thrombocytopenia.

The bone metastases of prostate cancer have a characteristic osteoblastic appearance on radiographs. Metastatic presentation with osteolytic lesions is rare with only a few case reports in the scientific literature describing this presentation.[6,7] This type of presentation may lead to delayed diagnosis because patients will be investigated for other causes of osteolytic bone lesions especially multiple myeloma. Our patient was 65 years of age, had bone pains, anemia and thrombocytopenia which could all have supported a diagnosis of multiple myeloma. In addition, the patient did not present with significant symptoms of bladder outlet obstruction which may otherwise have led us to suspect the prostate as the primary site. When evaluated for multiple myeloma, he had no lytic lesions in the skull bones or mandible and serum electrophoresis was negative for M-protein and there were no Bence Jones proteins in the urine. A bone marrow biopsy excluded the possibility of a non-secretory form of multiple myeloma. The presence of metastatic prostate cancer in the lesions was confirmed by the positive staining with PSA immunohistostain.

Our patient had a PSA level greater than 100ng/mL and an elevated ALP level of 509IU/L. PSA levels greater than 20ng/mL and ALP levels greater than 90IU/L have been found to be predictors for the presence of bone metastases among patients with prostate cancer.[11] The PSA is thought to play a role in the genesis of osteoblastic bone lesions by promoting the proliferation of osteoblasts and apoptosis of osteoclasts. With such an elevated PSA level our patient would have been expected to have predominantly osteoblastic lesions.

The pathogenesis of bone lesions in prostate cancer is not well understood. Prostate cancer cells promote both osteolytic and osteoblastic activity through production of factors that have direct or indirect osteogenic properties.[12] Factors such as bone morphogenetic proteins, endothelin-1, PSA and parathyroid hormone-related protein promote osteoblastic activity. The receptor activator of nuclear factor kappa-B ligand (RANKL) and its receptor (RANK) signaling promote osteoclastic activity while osteoprotegerin (OPG) protects the skeleton from excessive bone resorption by binding to RANKL and preventing it from binding to its receptor, RANK.[13] Prostate cancer cells express OPG and RANKL.[14] The RANKL to OPG ratio determines bone mass with a decrease in OPG resulting in excessive bone resorption. It is possible that in some patients with predominantly osteolytic bone lesions the RANKL to OPG balance is altered and hence the appearance of osteolytic bone lesions as was seen in our patient.

The treatment modalities of advanced prostate cancer are all palliative. Our patient received a blood transfusion and adequate pain relief medications. Androgen deprivation therapy is the standard of care for palliative treatment of prostate cancer.[15] It comprises surgical castration or suppression of luteinizing hormone-releasing hormone (LHRH) production. Pharmacological castration with diethylstilbestrol or LHRH agonists achieves testosterone levels similar to surgical castration; however, these agents are expensive and not readily available to most patients in low resource settings. Surgical castration may sometimes not be psychologically acceptable as was the case in our patient.

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