Why does a person with cancer feel so much pain? This is a pertinent question for many patients. During cancer treatment, pain can be caused by the disease itself, by procedures to combat tumors, or by diagnostic tests. Patients may also experience pain exacerbated by sadness, anxiety, and depression, which can worsen simple conditions and require specialized attention.
Oncologic pain can almost always be relieved or reduced and should not be considered a normal part of the disease. It is important to communicate what you are feeling to your oncologist and medical team, as pain control is important for the effectiveness of treatment.
For this reason, palliative care is part of cancer treatment and is essential, as pain-free patients sleep and eat better and maintain their daily activities, including physical exercise, which contributes to the success of oncologic therapy. Therefore, pain control is part of the treatment.
Pain can be managed by the oncologist, hematologist, and also by the palliative care team. Some selected cases may be referred to an anesthesiologist specialized in pain management.
Learn what is done to alleviate the pain caused by cancer and its origin.
Pain in oncologic treatment according to its causes
The main pains felt by cancer patients, according to their causes, are:
Pains caused by the tumor
- Bone infiltration – is the most common cause of pain in cancer. It can manifest locally or at a distance and especially affects patients with multiple myeloma or with bone metastases – the most common being those from breast, prostate, and lung tumors. Tumor growth or secondary fractures can cause injury, compression, traction, or laceration of nervous structures, leading to ischemic, peripheral neuropathic, or myelopathic pain;
- Compression of the spinal cord – when a tumor invades the spine, it can press on the spinal cord. The first sign is usually pain in the back of the neck or sore throat, sometimes with numbness or weakness in an arm or leg. This compression must be treated quickly to prevent other consequences;
- Compression or infiltration of peripheral nerves – infiltration or compression of trunks, plexuses, and/or nerve roots by the tumor can determine acute and intense pain. Neoplasms of the head and neck or metastatic lesions to the cervical lymph nodes can compress the cervical plexuses (in the neck region), causing local pain radiating to the nape or retroauricular region, shoulder, and jaw;
- Infiltration and occlusion of blood vessels and lymphatics – tumor cells can infiltrate and/or occlude blood vessels and lymphatics, causing vasospasm, lymphangitis (inflammation), and possible irritation of perivascular afferent nerves. Tumor growth near blood vessels leads to partial or total occlusion, producing venous stasis (inflammation in the skin) or arterial ischemia or both. Ischemia causes pain and claudication; and
- Infiltration of hollow viscera or invasion of ductal systems of solid viscera – the occlusion of organs of the digestive, urinary, and reproductive systems (stomach, intestines, bile ducts, ureters, bladder, and uterus) produces obstruction of visceral emptying and leads to contraction of smooth muscle, muscle spasm, and ischemia, producing constant diffuse visceral pain (like a colic), with a feeling of weight. Organs like the liver, pancreas, and adrenal glands may also present pain.
Pains caused by surgical treatment
- Surgical pain – Surgery is performed to treat cancers that have grown as solid tumors, but other treatments, such as chemotherapy or radiotherapy, may also be administered concurrently. Depending on the type of surgery, feeling pain is expected. However, there are medications that can be prescribed to alleviate or reduce pain; and
- “Phantom” pain – It is also an effect of surgeries involving the removal of a limb, such as a leg, arm, or even the breast. The patient may still feel pain or have other unusual or unpleasant sensations that seem to be coming from the absent part of the body. Phantom pain is real, not imaginary. It is important to communicate with the doctor and the pain management team.
Pain caused by other cancer treatments
- Peripheral neuropathy – pain, burning, tingling, numbness, weakness, or strange sensations in the hands, arms, legs, and feet can be caused by some types of chemotherapy drugs (or due to vitamin deficiencies and other health problems such as diabetes and infections);
- Mouth and throat pain – chemotherapy can cause sores and pain in the mouth and throat (stomatitis or mucositis). If the pain is severe and uncontrolled, it can prevent the patient from eating, affecting their overall health; and
- Radiation therapy pain – depending on the area where the radiation therapy is applied, mucositis (mouth sores), skin burns, and other painful injuries can occur.
Pain due to procedures and exams
Diagnostic exams for cancer can be painful, but this should not prevent them from being performed. All pains can be treated and relieved.
Types of pain during cancer treatment
The intensity of pain varies from person to person and also throughout the day or night. Understanding the type of pain helps in choosing the medication to alleviate it.
Acute pain – intense and lasts for a relatively short time. It usually disappears as the wound heals, for example;
Chronic or persistent pain – can range from mild to severe and is longer lasting. To be considered chronic, it must last more than three months;
Disruptive pain – “breaks through” the relief provided by analgesics. It typically appears quickly, lasts up to an hour, and feels very similar to chronic pain, but more intense. It can occur several times a day. Some people have disruptive pain when doing an activity like walking or getting dressed. For others, it occurs without any specific cause.
Pain management in cancer treatment
Opioid medications are typically used to treat moderate to severe pain in cancer patients. They are drugs similar to endorphins, natural substances produced by the body to control pain. They should be prescribed and used with great care due to the risks of interactions with other medications or alcoholic beverages.
Not every patient experiences side effects associated with opioids, but when they occur, the most common ones are drowsiness, nausea, vomiting, and constipation in the first days of use. Many of these effects improve after the first week, while others may require treatment for control. Other less common side effects include itching, mental effects (such as nightmares, confusion, and hallucinations), slow or shallow breathing, or difficulty urinating.
Opioids should not be stopped suddenly. Tapering off is done gradually, with medical assistance, to avoid reactions such as excessive sweating and diarrhea.
Non-opioid medications control mild to moderate pain.
The most common types of non-opioid medication are dipyrone (analgesic and antipyretic, used alone or to enhance the effect of opioids), paracetamol (relieves pain but does not reduce inflammation), and nonsteroidal anti-inflammatory drugs (NSAIDs) (generally should be avoided by those allergic to aspirin or any other NSAID, those undergoing chemotherapy, those taking steroids, lithium, blood pressure medications, or blood thinners, those with stomach ulcers or a history of ulcers, and those with kidney problems).
Other medications that can be used during cancer pain treatment:
- Antidepressants – to treat tingling or burning nerve-related pain, which can be caused by surgery, radiotherapy, chemotherapy, or the tumor itself;
- Antihistamines – help control nausea, aid in sleeping, and control itching;
- Anxiolytics – used for severe pain accompanied by muscle spasms and to reduce anxiety;
- Stimulants and amphetamines – enhance the action of opioids in pain control and reduce the drowsiness they cause;
- Anticonvulsants – help control tingling and burning nerve-related sensations; and
- Steroids – relieve bone pain, pain caused by spinal cord compression and brain tumors, and pain caused by inflammation.
Complementary therapies for pain control during cancer treatment
Many patients wonder what they can do to reduce cancer pain. Patients experiencing pain should always inform their doctor so that the best course of action can be determined. Alongside medications, alternative methods can be adopted to help control pain. The main ones are:
- Acupuncture – can help with controlling nausea caused by chemotherapy and with pain itself;
- Massage – reduces stress, anxiety, depression, insomnia, and pain;
- Meditation – has an effect on pain, anxiety, and high blood pressure by relaxing the body and mind;
- Yoga – can help alleviate some cancer symptoms and control pain.
Myths and truths about pain and cancer treatment
Using pain medication causes dependence.
MYTH. This does not occur if the medication is prescribed and the patient strictly follows the treatment plan.
Those who use opioids are already in a terminal state of cancer.
MYTH. In addition to being untrue, this contributes to the stigma associated with opioids.
Patients who endure pain are stronger and will overcome the disease more easily.
MYTH. Enduring pain without taking medication to consider oneself “strong” can actually harm the treatment and jeopardize the chances of success.
Talking about pain interferes with the doctor’s decisions regarding cancer treatment.
MYTH. The specialist is trained to prescribe medications that do not interfere with the ongoing treatment plan.
Pain should be controlled from the earliest symptoms.
TRUE. The earlier it is controlled, the better the patient’s quality of life and the greater the chances of treatment success.
