What is Cancer Pain?
Pain is an unpleasant physical sensation usually associated with injury or harm to the body.
People with cancer may have pain from the cancer itself or from treatments like chemotherapy, surgery or radiation therapy. Nerve pain or neuropathic pain is common in people with cancer and is caused by changes in nerve function from the cancer or its treatment.
Short term pain that lasts for hours or weeks is called acute pain. Pain that lasts longer than three months is called chronic pain.
Most chronic cancer pain is from the tumor pressing on nerves, bones, soft tissue or organs. Other causes include:
- Blockage in the intestines or urinary system
- Immune or hormonal changes
- Inflammation inside the body
- Damaged nerves from chemotherapy
- Damaged bones from steroid medicines
- Nerve injury from surgery
- Phantom pain is when a person feels pain in a part of the body which is no longer there, e.g. pain after limb removal
- Lymphoedema - swelling in one or more limbs from built-up fluid
Most acute cancer pain has an identifiable cause which can be a result of treatments and tests to find out more about the illness. The cancer itself can also cause acute pain. Examples include:
- Burning pain from injected medicines
- Numb hands and feet (neuropathy) and painful inflammation in the digestive tract (mucositis) from chemotherapy or radiation therapy
- Fractures from cancer in the bones
- Blockage of an internal body part
- Infections like shingles or fungal infections
- Bleeding in a tumor
- Deep vein thrombosis (DVT)
- Pain from lumbar puncture and biopsies to find out more about the cancer
People feel pain differently depending on the type of pain they have. The pain may be there all the time or it may come and go.
People with nerve (neuropathic) pain describe it as stabbing, prickling, burning, tingling or like “pins and needles”.
Bone pain is aching, dull and throbbing and is usually worse at night.
Soft tissue pain affects the muscles, skin and joints. It feels throbbing, sharp and aching.
People feel internal organ pain (visceral pain) in the trunk of the body; it is described as deep, squeezing, sickening or dull.
Cancer pain can affect most parts of a person’s life. It is often difficult for people with pain to socialise and carry out normal day-to-day activities like working, hobbies, cooking, bathing and sleeping. Cancer pain is upsetting and can lead to depression and anxiety.
Some cancer pain can be a sign of a serious problem in the body. It’s important to see a doctor you have any of these symptoms:
- Sudden or severe pain
- New pain
- Change in the type or location of pain
- Long term pain that gets worse or does not get better with treatment
The goal of treatment is to control pain so people with cancer can have a better quality of life.
Doctors use information about the patient and the disease to choose the right pain treatment, such as:
- How the patient describes the pain
- Patient history
- Physical examination
- Results of tests and imaging
- Cancer treatment
Medicines for Cancer Pain
Doctors usually use opioid medicines to treat cancer pain such as:
Non-opioid painkillers such as paracetamol, ibuprofen and naproxen are also commonly used.
Medicines which are usually used to treat other conditions like steroids, antidepressants and medicines for bone problems can also help with some types of cancer pain.
Medicines for cancer pain may be taken orally, injected or absorbed through the skin via a patch.
Other Treatments for Cancer Pain
When pain is a direct effect of the tumor, chemotherapy, radiation therapy or surgery can provide relief.
Nerve block, trigger point injection, spinal cord stimulation, physical therapy and massage are other options for some types of cancer pain. Your doctor will be able to provide more information about these treatments.
Treatment with Medical Cannabis
Pain is felt when nerve cells detect a problem somewhere in the body and send a signal through the spinal cord to the brain. The brain translates this message into the sensation of pain.
The endocannabinoid system is part of this signalling process. It is thought that cannabis can suppress pain by interacting with the endocannabinoid system, specifically the CB1 receptor.
The cannabis plant contains many compounds which affect the human body in different ways. Cannabinoids THC (Δ9- tetrahydrocannabinol) and CBD (cannabidiol) are the most abundant active compounds. THC is responsible for most of the mind-altering effects of cannabis.
Various forms of cannabis and cannabinoids have been tested in studies on pain, however very few were conducted in cancer patients.
- Improving Quality of Life With Nabilone During Radiotherapy Treatments for Head and Neck Cancers: A Randomized Double-Blind Placebo-Controlled Trial.
This trial looked into the effects of nabilone on the quality of life of cancer patients, including pain. Nabilone is a man-made compound similar to THC. This trial was double-blind which means neither the patients nor the staff knew which treatment was administered.
56 patients receiving radiation therapy for head and neck carcinomas were given either nabilone or a placebo each week during radiation therapy and for four weeks after radiation therapy.
Results found that at the dose tested, nabilone was not more effective than the placebo for relieving symptoms associated with pain, nausea, loss of appetite, weight, mood and sleep
- Nabiximols for opioid-treated cancer patients with poorly-controlled chronic pain: a randomized, placebo-controlled, graded-dose trial.
This double-blind study looked into the effect of nabiximols on people with advanced cancer and pain that responds poorly to opioids. Nabiximols is a specific extract of cannabis, and contains THC and CBD.
263 participants were divided into four groups and given a placebo, low-dose nabiximols, medium-dose nabiximols or high-dose nabiximols for five weeks. Questionnaires were used to record average pain, worst pain and sleep disruption.
Results found that the proportion of patients reporting pain relief was greater for nabiximols than for placebo overall, particularly in the low-dose and medium-dose groups. Unwanted effects were dose-related; only the high-dose group compared unfavourably to the placebo.
- Multicenter, double-blind, randomized, placebo-controlled, parallel-group study of the efficacy, safety, and tolerability of THC:CBD extract and THC extract in patients with intractable cancer-related pain.
This double-blind study compared the efficacy of a THC:CBD extract and a THC extract with placebo for relieving pain in patients with advanced cancer.
177 participants with cancer pain that was not adequately controlled with opioids were divided into three groups and given either the THC:CBD extract, the THC extract or a placebo for two weeks. They recorded their pain severity on a numeric scale.
Results found that THC:CBD performed better than the placebo (improvement of -1.37 vs. -0.69), whereas the THC group showed a nonsignificant change (-1.01 vs. -0.69). Twice as many patients in the THC:CBD group had a reduction of more than 30% from their original pain score in comparison with placebo.
Both treatments were well tolerated. 60% of patients experienced side effects including somnolence, dizziness and nausea, mostly of mild or moderate severity. One patient experienced fainting most likely due to THC.
Long term effects of cannabis usage and interactions with other medicines are not yet fully understood. Further clinical trials are needed before any conclusions can be drawn on the use of cannabis products in cancer pain.
References available at end of page.
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Related Advocacy Groups
There are several organizations in Australia which provide information and support to people with cancer and their families. Below are links to their websites:
Breast Cancer Network Australia
National Breast Cancer Foundation