The National Cancer Institute (NCI) of the National Institutes of Health (NIH) publishes an e mail blog entitited Current Contents to which one can subscribe. On January 23rd, their blog focused on non-opiod methods of managing cancer pain (see below). Pain is a common and much-feared symptom among people being treated for cancer and long-term survivors. Cancer pain can be caused by the disease itself, its treatments, or a combination of the two. It may be short-lived or chronic, and for some people it can persist long after treatment ends.
The most common cancer types, such as breast, lung, prostate, and colon cancer, rarely cause pain at the site where they originate. One of the most common types of cancer pain is bone pain. Cancer-induced bone pain occurs when metastatic tumors of cancers that start in other parts of the body grow in the bone marrow, the sponge-like tissue in the center of most bones. In fact, bone pain may be the first symptom of several forms of cancer, including prostate and lung cancer.
Researchers have found that “tumors in bone stimulate the sprouting of pain-transmitting nerve fibers near the tumor. Once tumor cells are established in the bone marrow, they hijack the molecules that regulate cells involved in breaking down bone, called osteoclasts. As a result, the osteoclasts get bigger and then they avidly digest bone. To digest bone, osteoclasts create an acidic environment that is almost like pouring battery acid on bone. The causes of bone cancer pain are twofold. First, sensory neurons, or nerve fibers, in bone “detect the acidic environment and signal it as pain. Second, excess osteoclast activity results in microfractures or full fractures of bone that can cause extreme pain.”
Denosumab (Prolia) and bisphosphonates like alendronate (Fosamax), are both first-line therapies for cancer-induced bone pain caused by metastatic cancer. Both denosumab and bisphosphonates, which were originally developed to treat osteoporosis, help maintain bone integrity by reining in osteoclast activity. A potential new treatment for bone pain due to metastatic cancer is an antibody called tanezumab, which blocks the activity of a pain-signaling molecule called nerve growth factor (NGF). Researchers found that in mice, tanezumab blocks nerve-sprouting in bone and reduces the development of late-stage cancer pain. Tanezumab is now being tested in phase 3 clinical trials for cancer-induced bone pain. A related approach seeks to block the actions of NGF by blocking its receptor, known as TrkA (tropomyosin receptor kinase A), on sensory nerve fibers. There is also keen interest in using cannabinoids, chemicals found in marijuana, to treat cancer-induced and other types of bone pain but this research is still in the stage of animal testing.
The NCI article below also describes chemotherapy-induced peripheral neuropathy (CIPN), often an undesirable side effect of chemotherapy. This is often the reason that patients must reduce their chemotherapy dose or stop treatment prematurely. Other sections in the NCI blog include non-drug approaches to relieving pain and other challenges to pain management.
The entire NCI blog can be found at the following link.