A new metastatic breast cancer diagnosis can be overwhelming. Focusing on what’s in front of you and what you might expect from living with the disease may help. Knowing about potential side effects of chemotherapy, such as back pain, can help you recognize and manage issues sooner and make it easier to cope.

Chemotherapy is a long-standing treatment option for metastatic breast cancer. As crucial as it is in increasing survival (and progression-free survival), chemotherapy can have a wide range of side effects and long-term complications.

Chemotherapy can cause nerve pain and may lead to sciatica-like symptoms, such as pain running down the back, legs, and feet. “After chemo, I really thought something was going on with my leg, as the bone pain in my shin just kept getting worse,” one MyBCTeam member wrote. “It turned out to be pressure on my sciatic nerve.”

The pain can be intense and persistent and may lower your quality of life. New or worsening symptoms should be checked by your healthcare provider right away to rule out serious complications.

What Is Sciatica, and What Does It Feel Like?

Sciatica is a pain that radiates along the sciatic nerve. The sciatic nerve starts in the lower back and extends down the hips and buttocks to the back of each leg. Sciatica is most often caused by a pinched or compressed sciatic nerve, which leads to inflammation and pain.

The pain can range from mild to severe and is often described as a sharp, radiating pain in the hips and lower back that feels like burning or an electric shock. Compression on the nerve from improper back support while sleeping can lead to nighttime or morning back pain. Sometimes, sciatica can lead to tingling or numbness in the leg.

How Members Describe It

Many MyBCTeam members have shared their experiences with sciatica. Some say the pain is relentless and unbearable, while others describe it as a dull ache:

“I went in to have my fifth round of chemo. Fifteen minutes in, I felt a pain that started in my back and ran around to my side and down my leg. It was unbearable.”

“The pain is from the foot up to my buttock, but the worst is the back of the thigh. I am taking tamoxifen but not sure that is it.”

“I have been having sharp shooting pain in my left leg. It started as a gradual dull pain around my butt area then went all the way down my leg to my ankles. Can this be related to the chemo and anastrozole I’m taking?”

“My sciatic pain started midway through my first six chemo treatments and has now progressed to the point where I can hardly function.”

Because sciatica affects people differently, tell your oncology team about any new or worsening symptoms, such as low back pain that spreads down your leg, as soon as they happen.

Nerve Damage From Chemotherapy and Sciatica

Although chemotherapy can slow the progression of many types of cancers, it can also cause a variety of side effects, some of which can be severe. Certain breast cancer treatments have been shown to affect the nervous system.

Chemotherapy-Induced Peripheral Neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is nerve damage caused by chemotherapy. It can lead to numbness, tingling, and pain in the hands or feet, often described as pins and needles. CIPN can lead to muscle weakness and balance problems that may place additional strain on the lower back and sciatic nerve.

CIPN can interfere with simple activities, such as picking up an object or buttoning a shirt. It can also lead to serious complications, such as dangerous falls.

Certain types of chemotherapy drugs are more likely to cause nerve damage. Medications widely used in breast cancer treatment that can cause nerve damage or changes include:

• Platinum-based drugs — Cisplatin, carboplatin, and oxaliplatin
• Taxanes — Paclitaxel and docetaxel
• Vinca alkaloids — Vincristine and vinorelbine

How Common Is CIPN?

The likelihood of developing CIPN depends on the type of chemotherapy drug, its dose, schedule, and whether it’s given with other chemotherapy drugs. Your previous treatments (surgery, radiation, and chemotherapy) and other health conditions also play roles. However, CIPN is one of the most serious complications associated with anticancer drugs.

CIPN occurs in 57 percent to 83 percent of people who’ve received taxanes. Of those people, 2 percent to 33 percent experience severe neuropathy. CIPN typically starts within the first two months of chemotherapy and can last for months to years.

Taxane Acute Pain Syndrome

In many cases, CIPN develops from acute (early-onset) pain, usually in the hips, legs, and feet. Taxane chemotherapy drugs often cause this type of pain, called taxane acute pain syndrome (TAPS), which is also known as paclitaxel-associated acute pain syndrome or taxane-induced myalgia-arthralgia syndrome.

TAPS pain is often described as sharp, burning, and radiating, and it usually goes away in a few days.

TAPS has been reported in many people undergoing taxane chemotherapy, and estimates vary by study. The symptoms generally start within 24 to 48 hours of receiving taxane and can last up to a week. The syndrome is believed to be caused by toxic effects of the drug and inflammation. TAPS may be associated with later CIPN in some studies.

Aromatase Inhibitor-Induced Musculoskeletal Symptoms

Aromatase inhibitors, such as letrozole, anastrozole, and exemestane, are effective at lowering the risk of breast cancer after menopause.

These hormonal therapies are sometimes combined with cyclin-dependent kinase 4/6 inhibitors, a type of targeted therapy that helps slow cancer cell growth. Examples include abemaciclib, palbociclib, and ribociclib.

Aromatase inhibitors are medications that lower estrogen levels. They can cause arthralgia (joint pain) in the hands, knees, back, hips, and shoulders. This is called aromatase inhibitor-induced musculoskeletal symptoms (AIMSS).

AIMSS can also cause stiff joints and sore, weak muscles. Aromatase inhibitors work by lowering the body’s estrogen levels, which has been shown to reduce bone density and increase the risk of arthralgia and osteoporosis.

Although the pain caused by aromatase inhibitors is more of a stiffness than the sharp pain of neuropathy, muscle weakness, and inflammation caused by these drugs can affect the lower back and sciatic nerve. As a result, symptoms that resemble sciatica can develop.

One small study found that 47.7 percent of participants with breast cancer who were on hormone therapy experienced muscle and joint pain.

Back Pain From Spinal Metastases

Breast cancer that’s spread to the spine can also cause back pain. Metastatic breast cancer, by definition, is breast cancer that metastasizes (spreads) to another part of the body, commonly the lungs, bones, liver, or brain.

Breast cancer that spreads to the bone (bone metastases) often affects the spine. When this happens, it’s known as spinal metastases.

Studies have shown that about two-thirds of bone metastases are spinal metastases, and one-third of spinal metastases cause symptoms, including:

• Pain
• Neurological issues
• Balance issues

Pain occurs most often, affecting approximately 90 percent of people with spinal metastases from metastatic breast cancer. These symptoms can be debilitating and greatly impact quality of life.

The type of spine or back pain you have can give doctors clues about where the tumor is and how serious it may be. For example, shooting or burning pain may mean the tumor is pressing against or irritating certain nerves. Constant, deep, aching back pain that gets worse at night may be a sign of tumor growth or swelling caused by the tumor.

Talk to your oncologist if you have back pain, whether or not you’re receiving chemotherapy. They can help find the cause and recommend a plan to relieve the pain.

How To Manage Sciatica and Lower Back Pain

Lower back pain and sciatica caused by chemotherapy and hormone therapy drugs can greatly diminish quality of life during breast cancer treatment. Sometimes chemotherapy and hormone therapy drugs need to be used long term, making strategies to manage the painful side effects even more important.

Treatment options for CIPN may differ from true sciatica. Your healthcare team will help you determine the right medication plan for you. To relieve pain and symptoms of nerve damage, your doctor may recommend drugs such as:

• Pain relievers, including nonsteroidal anti-inflammatory drugs (NSAIDs)
• Anti-seizure medications, such as gabapentin or pregabalin
• Antidepressants, such as duloxetine
• Corticosteroids to control inflammation
• Pain-relieving patches or cream, such as lidocaine or capsaicin

Ways to manage pain without medication include physical therapy and exercise, which can help improve mobility, balance, and coordination, as well as practices like acupuncture and massage.

Some researchers suggest that cancer rehabilitation should start with prehabilitation — getting ready for treatment before you start it. The goal of prehabilitation is to boost physical and mental health as much as possible before chemotherapy, radiation, or surgery lowers them.

Speak With Your Care Team

If you develop nerve pain during or after receiving chemotherapy, it’s important to talk to your doctor right away to prevent serious complications and permanent nerve damage. It’s also important to rule out the possibility that your pain is caused by another serious medical condition. Your doctor can help you find ways to manage chemotherapy side effects and live well.

Join the Conversation

On MyBCTeam, people share their experiences with breast cancer, get advice, and find support from others who understand.

Have you had back pain since starting chemotherapy? Let others know in the comments below.