Stage 4 breast cancer occurs when cancer first shows up in the breast, and then metastasizes, or spreads to other areas of the body. Common areas for metastases include the lymph nodes, chest wall, bones, lungs, liver, and brain. Other terms for this condition include “advanced” or “metastatic” breast cancer.

By definition, stage 4 breast cancer involves complications, as it has already moved beyond the original cancer site. But additional complications can occur, either directly from the cancer itself, or due to treatments the patient receives. These complications may vary depending on the type of cancer, where it has spread, and what treatment methods are in use. Some common complications include:

  • cancer-related pain
  • skeletal (bone) complications
  • treatment-related complications, such as lymphedema, pain, and sickness

Cancer can cause pain all on its own, as tumors grow and take over formerly healthy areas of the body. The cancer can put pressure on organs, nerves, and bones, causing aching or sharp, stabbing pain. Some types of cancer even secrete certain chemicals that can cause painful sensations.

Breast cancer often spreads to the bones, and there can be a number of skeletal complications as a result. These problems are often caused by bone resorption, a normal process of breaking down bone. In healthy young people, bone is rebuilt at the same rate as it is broken down. In older adults and those with metastasis to the bones, the resorption process occurs more rapidly.

Bone pain

A painful, aching feeling in your bones is often the first sign that cancer has spread to the bone. As the condition progresses, resorption causes a thinning and weakening of the bones. When the bones become too weak, fractures can occur, sometimes without any major injury causing the damage.

Spinal compression

When cancer cells grow in or near the spine, they can put pressure on the spinal cord and adjacent nerves. This pressure can cause pain in the back or neck, numbness or tingling, and difficulty walking. Sometimes it can lead to difficulty controlling the bladder and bowels. Though spinal compression is less common than other bone complications, it can be very serious.


Hypercalcemia refers to elevated levels of calcium in the blood. This occurs when the rate of resorption increases, and the calcium from the bones is released into the bloodstream. Hypercalcemia can lead to serious problems, such as:

  • kidney stones
  • kidney failure
  • irregular heartbeat
  • neurological problems, including confusion, dementia, or coma

Treating bone complications

A certain class of drugs, called bisphosphonates, works to slow the rate of resorption. They work by destroying osteoclasts, the cells responsible for resorption.This helps to lower blood calcium levels, slow the weakening of bone structure, and lessen bone pain.

Because cancer treatments involve the killing and/or removal of abnormal and normal cells from the body, there are usually unpleasant side effects that go along with them. In some cases, a person may feel like the treatment is even worse than the cancer. It’s important to realize that the pain and discomfort of treatment will go away. Healthy cells do recover.

Cancer treatments can cause pain and sickness. Chemotherapy treatments may result in mouth sores, nausea, nerve damage, and diarrhea. Radiation therapy can lead to burning pain and scarring. Surgery is, of course, painful and requires significant time for recovery.


When doctors remove lymph nodes to check for cancer cells, it disrupts the flow of lymph fluid in the body. If not enough lymph nodes are left to properly drain fluid from a particular area, a form of painful swelling called lymphedema can occur.

Relieving treatment-related complications

Lymphedema is best caught early. It can be treated with physical therapy, massage, or a compression sleeve. Pain can be treated with over-the-counter pain relievers, or a doctor may prescribe a stronger painkiller. Side effects from chemotherapy can sometimes be treated with other medications.

You should let your doctor know any time you experience pain or other unpleasant complications from your cancer or your treatment. They can determine if the symptoms indicate a more serious problem, and can also work with you to manage symptoms and help you feel better, faster.