Back pain and other unusual signs of lung cancer

Early diagnosis of any cancer improves prognosis. That's why being aware of telltale symptoms and undergoing age- and risk-appropriate screenings where available can improve outcomes for many cancer patients. However, lung cancer typically has few symptoms early in the disease. By the time individuals notice something is wrong, their cancer is usually at an advanced stage.

"Many tumors in the lung never cause symptoms, and that's why, without screening, three-quarters of patients present with cancer [that is] too advanced for surgery because it's already spread," says Dr. David Gerber, associate professor of internal medicine and clinical sciences at UT Southwestern Medical Center. Doctors often catch early stage lung cancers incidentally, for example, when they are administering a chest X-ray for another reason.

Lung cancer symptoms are typically nonspecific, and they could indicate many other, less serious conditions. If you're a long-time smoker, you're probably used to a persistent cough, hoarseness, wheezing or shortness of breath, so you may not even think to see your doctor about these symptoms. In fact, you may not seek medical attention until you start feeling pain, at which point, lung cancer is past the early stage.

Read: What to Know About Biopsies for Lung Cancer.

"There are no nerve endings in the lungs, so you can have a large tumor in the lungs without noticing," says Dr. David Carbone, medical oncologist and director of the Thoracic Oncology Center at The Ohio State University Comprehensive Cancer Center – Arthur G. James Cancer Hospital and Richard J. Solove Research Institute. "Most lung cancer patients are diagnosed from symptoms that result from the spread [metastasis] of the cancer to another site, such as the spine or liver."

In fact, new and unexplained back pain is an important red flag to watch for. "If a patient with a history of lung cancer has new back pain, we should think about this seriously and get an image quickly to make sure the cancer is not in the spine," Gerber says.

"Lung cancer is one of the most common cancers to cause bone metastases, and it most commonly metastasizes to the spine," Gerber says. "This is very painful. There is a lot of blood flow to the spine and now there is [also] a tumor in the space." Lung cancers may also metastasize to other weight-bearing bones, such as the hip or femur, which is the big bone in the top of the leg. Patients may undergo radiation or surgery to treat these metastases.

Read: Understanding Targeted Therapies for Lung Cancer.

Carbone says there is a subset of lung cancers that erode into the chest wall as they grow. Unlike the lungs, the wall of the chest is very sensitive to pain. While these tumors are still local – they are contained within the chest and haven't spread – they can cause pain in the chest, shoulder or back. Approximately 25 percent of lung cancer patients experience chest pain, according to the International Association for the Study of Pain.

"Lung cancer metastases can also cause spinal cord compression, resulting in weakness or numbness in the legs," Gerber says. "Patients can have difficulties going to the bathroom, even paralysis."

But the bones are not the only place where lung cancer can cause symptoms. Other common sites of metastases include the brain and liver. In the brain, a metastasized tumor may produce headache, nausea or seizures. A liver metastases causes patients to lose their appetite, experience pain, lose weight or become jaundiced (yellowing of the skin and eyes).

A metastasized tumor can also constrict or entrap a nerve, causing pain or numbness going down the arm or hoarseness if it pinches a nerve in the larynx (voice box).

Lung tumors may also block other structures in the body. For example, if a tumor intrudes into the bronchial tubes, the main airways that deliver air to the lungs, it can cause coughing, shortness of breath or coughing up blood. A metastasized tumor that blocks the esophagus, the tube that connects the mouth to the rest of the digestive system, can cause difficulties swallowing. And a tumor that blocks the main vein between the heart and the upper chest (the superior vena cava) can make the blood back up in the lungs, face and arms.

Read: Do Filtered Cigarettes Lower the Risk of Lung Cancer?

Finally, in rare cases, lung cancers can cause syndromes – collections of symptoms – that are not directly related to the cancer. Paraneoplastic syndromes, for example, occur when the immune system reacts to substances the tumor produces, causing unexplained weight loss or a rare joint problem.

The best way to prevent lung cancer from spreading is to catch it at an early stage. For patients who smoke, or have a history of heavy smoking, (these are the people at the highest risk of developing lung cancer), screening can help detect early stage cancers. The U.S. Preventive Services Task Force and most other professional organizations recommend screening with low-dose CT scans beginning at age 55 for people with a 30 pack-year smoking history. (A pack year is the number of packs of cigarettes per day you smoked multiplied by the years you smoked. So if you smoked two packs per day for 15 years, you'd have a 30 pack-year smoking history.)