Bone Pain
Bone metastases can cause severe neuropathic pain or somatic pain. This type of pain is usually much more severe with movement or any weight-bearing activity. Bone pain requires a particularly careful assessment. If there is severe pain during any weight-bearing activity, a radiograph may reveal a potential for pathologic fracture for which orthopedic stabilization or radiation therapy may be needed.
Even in the absence of pathologic fracture, treatment of bone pain may benefit from discussion with various sub-specialists as there are multiple non-pharmacologic treatment options, including external beam radiation, systemic isotope therapy, or physical modalities such as bracing. When these are not appropriate or desirable to the patient, other options include opioid therapy, bisphosphonates, calcitonin, or radioisotopes.
Bisphosphonates reduce bone absorption and formation by inhibiting adhesion of tumor cells within the bone and inhibiting osteoclast function. Bisphosphonates may reduce the number of skeletal fractures, forestall the need for radiotherapy, and reduce the incidence of hypercalcemia and need for orthopedic surgery. Benefits are usually observed in patients who have been taking the medication for several months. IV bisphosphonates have greater bioavailability than oral agents. The full benefit is usually achieved within seven to 14 days, with 50% of patients achieving full response. The dose can be repeated every three to four weeks when clinically warranted. The optimal duration of therapy is unknown, but current guidelines indicate that the medications, when used, should be continued until there is no longer any clinical relevance.
Caution must be taken when using bisphosphonates for a patient with renal failure. There have been case reports of jaw osteonecrosis in persons on bisphosphonates for bone metastases or Paget's disease, most frequently after a recent dental intervention. Although clinicians should be aware of this rare side effect, the benefits may outweigh these risks when using these medications for persons with limited life expectancy.
External beam radiation therapy is a highly-effective palliative intervention for cancer-related bone pain. In addition, radiopharmaceutical therapies may alleviate painful, disseminated skeletal metastases unresponsive to other therapies. Palliative radiation therapy can relieve pain within the first few treatments and reaches maximum effectiveness by four weeks. Radiation is usually given in multiple treatment sessions over time to minimize long-term adverse effects for patients with long life expectancy. In cases where life expectancy is short, higher doses can be given in one or a few sessions to optimize symptom relief without excessive harm. The major toxicities of radiation therapy are related to the area being radiated (e.g., mucositis from oral radiation) and fatigue.
None of these adjuvants has proved to be more effective than opioids combined with NSAIDS. However, they can be very useful when pain is not responding to pharmacotherapy or side effects of analgesics are intolerable.