Skeletal metastases are frequent complications of many cancers, causing bone complications (fractures, bone pain, disability), which negatively affect the patient's quality of life. Here, we first discuss the burden of skeletal complications in cancer bone metastasis. We then describe the pathophysiology of bone metastasis. Bone metastasis is a multistage process; long before the development of clinically detectable metastases, circulating tumor cells settle and enter a dormant state in normal vascular and endosteal niches present in the bone marrow, which provide immediate attachment and shelter, and only become active years later as they proliferate and alter the functions of bone-resorbing (osteoclasts) and bone-forming (osteoblasts) cells, promoting skeletal destruction. The molecular mechanisms involved in mediating each of these steps are described and we also explain how tumor cells interact with a myriad of interconnected cell populations in the bone marrow, including a rich vascular network, immune cells, adipocytes and nerves. We discuss metabolic programs that tumor cells could engage with to specifically grow in bone. We also describe the progress and future directions of existing bone-targeted agents and report emerging therapies that have arisen from recent advances in our understanding of the pathophysiology of bone metastases. Finally, we discuss the value of bone turnover biomarkers in detection and monitoring of progression and therapeutic effects in patients with bone metastasis.
Prostate cancer is the most common malignancy in elderly men and is often complicated by osteosclerotic metastases. Bone scintigraphy is commonly used to assess the extent of bone metastases; its use is limited in monitoring of treatment efficacy because it is an expensive, time-consuming technique that does not reflect the rapid skeletal response to therapy (Coleman, 1998). The bone scan flare response following successful therapy also reduces the value of bone scanning in the early monitoring of treatment in prostate cancer (Pollen et al, 1984). The serum level of prostatespecific antigen is the most sensitive index of disease progression in most but not all patients, but does not reflect the effects of palliative treatments such as bisphosphonates for bone metastases in patients that escape from antihormonal therapy.The marked increase of osteoblastic activity in patients with osteosclerotic metastases is reflected by increased levels of serum total and bone-specific alkaline phosphatase (Pecherstorfer et al, 1995;Lorente et al, 1996). There is, however, biochemical (Myamoto et al, 1994, Sano et al, 1994Kylmala et al, 1995;Berruti et al, 1996;Ikeda et al, 1996;Takeuchi et al, 1996;Maeda et al, 1997;Nguyen-Pamart et al, 1997, Pelger et al, 1998 and histological (Urwin et al, 1985;Clarke et al, 1991) evidence of increased bone resorption in these patients even in the absence of overt osteolytic bone metastases. This increased bone resorption is of clinical relevance as it is the rationale for using bisphosphonates, a palliative treatment that has been shown to reduce bone pain in patients with progressive metastatic prostate cancer who no longer respond to hormonal therapy (Adami et al, 1985;Carey and Lippert, 1988;Clarke et al, 1992;Kylmala et al, 1993, Taube et al, 1994Pelger et al, 1998).In this study we assessed the level of bone resorption in patients with osteosclerotic metastases from prostate cancer before and after bisphosphonate treatment by using new sensitive and specific biochemical markers of bone resorption including a serum assay for type I collagen C-telopeptide breakdown products; and values were compared to those of bone formation markers. PATIENTS AND METHODSForty-eight patients with carcinoma of the prostate (age 71.7 ± 9.6 years, mean ± 1 s.d.) and nine with benign prostatic hyperplasia (BHP) (age 69.8 ± 4.2 years) were enrolled. All patients with cancer had a prostatic biopsy and tissue diagnosis of adenocarcinoma. Bone involvement and its extent was evaluated by bone scintigraphy using Technetium-99m labelled methylene bisphosphonate. When bone metastases were suspected, confirmation was obtained with standard radiographs, computerized tomography (CT) and/or magnetic resonance imaging. The metastatic load in Summary Although increased bone formation is a prominent feature of patients with osteosclerotic metastases from prostate cancer, there is also some evidence for increased bone resorption. The aim of this study was to compare the clinical utility of new bone resorption markers to tha...
At present, sampling of the lymph nodes or bone marrow for the detection of regions of metastatic disease in patients with breast cancer can only be undertaken at the time of initial diagnosis and surgery. However, the sampling of these tissues and the methods used are inaccurate, time consuming, and cannot be used for easy routine screening to determine disease recurrence and response to treatment. Because of the problems encountered with current methods and tissues sampled at the time of breast cancer diagnosis, this review discusses the urgent requirement for and potential development of a quick, simple, and accurate diagnostic test utilising the haematogenous system, a source of circulating tumour cells in patients with breast cancer, and highly sensitive molecular biological techniques, such as reverse transcription polymerase chain reaction. In addition, this review also highlights potential problems that may be encountered and should be avoided when devising such a test.
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