Bone cancer, as the name suggests, arises from the bone. It is usually a secondary or a metastatic form of cancer. Statistics suggest that about 30 to 50 percent of all cancer patients experience pain, and of those, up to 90 percent of patients with progressive cancer undergo significant, life- changing, cancer-induced pain. The most common types of cancers that more often lead to bone cancers are those of the breasts, prostate, and lungs. Bone cancer pain is also more difficult to treat than pain from most other forms of cancer.
The most common symptoms of bone cancer or bone metastasis are pain, pathologic fractures, hypercalcemia, and spinal cord compression. This type of pain can be very detrimental to a patient's quality of life. However, there are two types of pain in such patients ongoing pain and breakthrough or incident pain.
Ongoing pain is the first indication of bone cancer and begins as a dull, constant, throbbing pain that surges in intensity with the passage of time. This type of pain is aggravated by the use or movement of the affected bones. Pain increases as bone destruction from cancer continues over time; this is called incident or breakthrough pain. Excoriating pain can occur suddenly or frequently, often occurring after posture changes, weight-bearing activities or movement of the affected joints or limbs.
From the above mentioned types of pain, breakthrough pain is hardest to handle or control as the dosage of opioids needed to control this pain are generally higher than required to control ongoing pain. The higher dosages of medication can result in sedation, somnolence and constipation.
While there have been significant advances in cancer treatment and diagnosis, the basic neurobiology of bone cancer pain is poorly understood. Moreover, new perceptions into the risk factors and mechanisms that induce cancer pain are now emerging from animal studies. The elements originating from tumor cells, inflammatory cells, and cells derived from bone appear to be involved synchronously in driving this frequently difficult-to-control pain state. Moreover, our understanding of the mechanisms involved in the pathophysiology of bone cancer pain will improve both our capability to provide mechanism-based therapies and the quality of life of cancer patients.
There are a variety of therapeutic modalities and drugs used in combination or stand alone for the treatment of bone cancer pain such as nonsteroidal anti-inflammatory drugs (NSAIDs), opioids, bisphosphonates, radiation, and surgical intervention. Most advanced bone cancer pain requires, opioids which is the mainstay for analgesic therapy. However, there could eventually be an evolving opioid tolerance or an increase in the severity of the pain. Moreover, with advancement in research it is suggested that in conjunction to fluctuating doses of morphine required to alleviate pain, the use of palliative therapies such as focal radiation or chemotherapy suggest that the high opioid doses are a minor reflection of the intensity correlated with the bone cancer pain state.
Hence, a major drawback in dealing with opioids for advanced bone cancer pain is that doses needs to be escalated frequently as the same doses are often insufficient to block movement-evoked breakthrough pain.
To summarize the major developments in the prevention and treatment of bone cancer pain requires new understandings into the processes and mechanisms that initiate and maintain this debilitating pain state.