In this blog series, we present excerpts from Dr. David Stewart’s book A Short Primer on Why Cancer Still Sucks. If you would like to read Dr. Stewart’s 13 other reasons, plus what the future of cancer research might look like, copies are available through Amazon Books or at whycancerstillsucks.com.
Pain: It is one of the most feared complications of cancer. There are three main types of pain. Somatic pain comes from cancer damaging or compressing body parts like bone or skin that have lots of nerve fibers that carry pain signals. With somatic pain, the patient can usually point right at the area that is painful. Neuropathic or neuralgic pain results from the cancer invading or compressing nerves. Neuropathic pain is often more difficult to control than somatic or visceral pain. Visceral pain is from growth of a cancer in an inner organ like the lung, liver, or pancreas. When it does cause pain, the pain is vague and difficult to localize and describe. No matter what the type of pain, radiotherapy, and systemic therapies that cause even modest tumor shrinkage can be more potent pain killers than morphine. These therapies reduce pain by reducing the tumor’s pressure on surrounding structures and by enabling healing of damaged tissues. One major development over the past few decades has been the emergence of the specialty of palliative care, which has helped in the ways that pain can be controlled.
Weight loss and loss of appetite: Patients with some cancers (like cancers of the stomach and pancreas) are more likely to develop cachexia (weight loss) than are patients with other types of cancer. Since cancers rely on high amounts of glucose, some people have argued that eating a low sugar diet should help fight the cancer. The reason that this is unlikely to work is that the cancer can produce a ready supply of glucose for itself just by breaking down a patient’s normal tissues.
Immune cells release cytokines which break down, fat, muscle, and other body tissues. Cytokines can also suppress the brain’s appetite center. Additionally, they may alter the sense of taste, and may also interfere with the ability of stomach muscles to contract. If the stomach is not contracting properly, it can take a long time for the stomach to empty.
Depression and anxiety, common psychological side effects of a breast cancer diagnosis, can also decrease appetite.
Researchers have investigated a few ways to manage low appetite to help cancer patients. For example, corticosteroids like prednisone or dexamethasone may markedly stimulate the appetite; however, corticosteroids can also cause problems, particularly if they are continued for a long duration of time. Marijuana and cannabis derivatives have also been assessed for their ability to improve appetite, but there is little evidence that they help much. Making a patient’s tumor shrink with therapy may improve appetite and weight loss.
Fatigue/weakness: Increased fatigue is often one of the early symptoms of cancer. A cancer can cause fatigue by wasting a body’s energy and by causing muscle breakdown. While both systemic therapies and radiotherapy often directly cause fatigue, many patients notice a substantial improvement in their energy level as their cancer shrinks. Another very important factor in combating fatigue is to stay as active as possible and maintain muscle mass. We now know that inactivity leads to increased muscle loss, and this worsens not only fatigue but also increases the risk of other problems, including confusion/delirium, blood clots, pneumonia, and bed sores.
Cancer and cancer treatment can also cause low hemoglobin (anemia) that can contribute to fatigue. Some cancers also release substances that make the blood calcium level go up or that make sodium levels go down. High calcium levels and low sodium levels can cause drowsiness, weakness, and confusion. Treatment of the cancer, using transfusions to correct low hemoglobin levels, and using other approaches to correct high calcium or low sodium can all help with management of cancer-related fatigue.
Infection: Infections are very common in cancer patients. Cancers may cause infections by eroding through barriers, such as the skin or the lining of the gastrointestinal tract. This erosion permits bacteria to invade into deep tissue that are normally protected by these barriers. Another way that cancers can increase the risk of infection is by blocking the normal flow of body fluids. Usually, body fluids flush out bacteria that enter the urinary tract, lung, lymphatic system, and biliary system. If fluid flow is blocked by a growing tumor, the fluid can stagnate, permitting the bacteria to grow and cause an infection. As cancers grow, they may also suppress the immune system. This can increase the risk of reactivation of some viruses, such as the herpes zoster (chicken pox) virus that causes shingles.
Swelling: Swelling (also called edema) is very common in patients with advanced cancer. It can arise in several ways. For example, increased pressure in veins (due to blockage by a blood clot or tumor) or lymphatic channels (due to blockage by tumor or scar tissue) will increase pressure within the veins or lymphatic channels. This can lead to leakage of fluid into surrounding tissues. Also, if the main vein draining the upper part of the body (the superior vena cava, or SVC) is compressed by a tumor, this may cause edema of the face and arms. Edema can also be caused by increasing leakiness of capillaries and by decreased blood albumin levels in patients with cancer. Inactivity also increases edema. Muscles contracting while walking help force tissue fluids back into the blood stream, and inactivity decreases these muscle contractions. If a person spends most of the day sitting, gravity will also contribute to development of leg edema. Patients who cannot lie down to sleep due to pain or shortness of breath will also develop leg edema.