CANCER RELATED BONE PAIN

Introduction: Bone pain due to cancer is caused by primary bone tumors and those malignant diseases that commonly metastasize to the bones. The skeleton is one of the most common sites of tumor metastases. Metastatic cancer invades bone in 60%–84% cases. Up to 80% of all bone metastases are related to cancer of the breast, prostate, lung, thyroid, and kidney. Pathophysiology of bone pain: There are 3 main mechanisms by which the skeleton is affected by cancer that include: 1- primary bone cancer 2- direct invasion from adjacent primary tumors 3- bone metastases. There are 4 Steps in the development of a painful bone metastasis: 1-Arrest of metastatic cell in bone marrow 2- Extravasation and growth in interstitium 3- Invasion and growth in bone 4 –Nociception . Bone pain syndromes: include - Continuous bone pain - Incident pain ( movement or spontaneous breakthrough pain ) - Mixed bone and neuropathic pain - Mixed bone and visceral pain Bone pain in cancer patients may induced by: Metastases , Fracture , Degenerative bone disease , Bone marrow pain , Nonmetastatic hypertrophic osteoarthropathy and Other bone disease. Evaluation of the Patient with Bone Cancer : The two most important imaging modalities in the evaluation of bone malignancy are plain radiography and nuclear bone scan. Computed Tomography (CT scan) is most useful in evaluation of the pelvic and shoulder girdles as well as lesions involving the spine. MRI is most beneficial in the evaluation of tumor infiltration of muscle and bone marrow, in the evaluation of spinal cord compression. Treatment: These patients require multimodal therapy consisting of the management of the primary cancer, analgesics, and/or measures to prevent further osteolysis and/or fractures. It is important to know about the site and distribution of bone metastases and its sequelaes (pathologic fracture and spinal cord compression). Any treatment should be directed at tumor regression, relief of cancer-related symptoms, and preservation of functional capacity. In some cases metastatic disease is so advanced as to be resistant to chemotherapy or radiotherapy. Time to pain relief and other beneficial effects vary with different types of treatment. This may influence the choice of treatment in an individual patient; for example, if life expectancy is very short, bisphosphonates, radiotherapy, or radioisotopes may not be appropriate Nonsteroidal anti-inflammatory drug (NSAIDs) Oncogenes, cytokines, growth factors, and chemotherapy all promote COX-2 transcription.Thus, COX inhibitors, NSAIDs and the newer COX-2 inhibitors should be effective in reducing cancer-associated pain and slowing cancer progression. Bisphosphonates bisphosphonates (e.g., clodronate and pamidronate) have been shown to reduce bone pain arising from metastatic breast cancer and myeloma. There are some evidence ( level 1 and 2 ) demonstrate that bisphosphonates have Clinical effects on Analgesia , Prevention of osteolysis and bone metastasis , and also can improve survival. Corticosteroids Corticosteroids have analgesic effects in the treatment of metastatic bone pain. This analgesic effect occur through the blockade of cytokine synthesis which contributes to both inflammation and nociception. Calcitonin The calcitonin has the potential to relieve pain and also retain bone density, and decrease the risk of fractures. Because of its rapid onset of action, it may have an advantage in individual patients with severe acute bone pain or in those with a very short prognosis. Opioid analgesics Bone pain usually responds well to opioids. opioids are the mainstay treatment for symptom control of isolated bone involvement areas and for diffuse bone pain. A regular dosing of an opioid is advised for continuous pain. In addition, a breakthrough or rescue dose should be prescribed for breakthrough pain on an as-needed basis. Some studies suggest that morphine may increase pain, osteolysis, bone loss, and spontaneous fracture. Adjuvant Analgesics Some of agents typically used to control neuropathic pain are useful in the control of bone cancer pain. Hormonal Therapy Progression of metastasis from breast, prostate, and uterine malignancies are hormone dependent . Antitumor hormonal treatment deprives these tumor cells. Procedural Interventions: - Intralesional Injection - Percutaneous Vertebroplasty /Kyphoplasty - Rhizotomy - Radiotherap - Orthopedic surgery - chemotherap - Radionucleotide