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Bone Metastases in Lung Cancer: An Introduction

February 17, 2007 - 4:50 pm email to a friend printer friendly view / write comments

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Dr. West

I’ve discussed the general management of metastatic lung cancer, both SCLC and NSCLC, but there are also several common complications that sometimes require particular management. Bone metastases, for instance, may be treated by the same “whole body” approach with chemotherapy that treats other areas of tumor involvement, but may also benefit from additional approaches. Bone metastases are common in oncology, and approximately 30-40% of lung cancer patients develop bone metastases at some point, about half presenting with evidence of bone involvement at the time of diagnosis (bone metastases general review abstract here). These metastases often have a significant impact on a patient’s quality of life, leading not only to pain but also a risk for pathologic fractures (bone breaks because the bone is weakened by cancer involvement leading to reduced structural integrity), potential compression of the spinal cord and other nerves, and high blood calcium levels as bone is broken down (which can lead to confusion, constipation, numbness/tingling, and other problems). With bone metastases comes a risk of impaired mobility, problems with sleeping and eating normally, and a somewhat worse prognosis overall, although there’s a lot of variability in the population.

Treating the underlying cancer with chemotherapy and/or targeted therapy (systemic, or “whole body”) can also lead to improvement in disease in the bones, but sometimes local therapy is indicated. The goals of treating bone disease are primarily to relieve pain and to reduce the risk of fracture, which tends to occur in “weight-bearing” bones like the legs, hips, and spine.

Of the patients with lung cancer who ultimately develop bone metastases (somewhere in the range of 50% of patients with advanced disease), the metastases are without symptoms in 30-60% initially, which leads to this being an underdiagnosed and undertreated problem. The majority of these are in the spine (thoracic or lumbar vertebrae, mainly), ribs, and pelvis; and less likely but sometimes seen the cervical spine (in the neck), femurs (thighs), humerus (upper arm), scapula (shoulder blade), skull, sternum. It’s fair to say that they can be anywhere in the spine, but more likely in the torso, and in the extremities more likely to be higher up.

The most common way to detect bone metastases used to be bone scans, but they used less and less now as PET scans have become more widely available. Bone scans are falsely positive (light up as abnormal but not really cancer) in the setting of prior trauma or degenerative joint disease, and many people have one or more of those, so it can be very difficult or impossible to tell if the spine abnormality on the bone scan is metastatic disease or just garden variety disk disease, the kind that makes back pain one of the top reasons for people to see a health care professional. PET scans are more sensitive (able to pick up disease better) and more specific (what they pick up is more likely to really be cancer) (one abstract on PET for bone mets here), and they’ve become much more widely available. However, many if not most PET scans stop at the mid-femur level, so it’s possible to miss disease lower down in the legs – an uncommon but certainly possible place to develop bony metastases.

Often, those scans still can’t definitely proclaim an abnormal area as cancer. MRI scans are often very, very good at determining details of bony disease and clarifying whether an abnormality is cancer or degenerative changes. Some people can’t undergo an MRI scan because they’re loud and pretty tight, leading about 10% of people just unable to tolerate the close confines. CT scans with “bone windows”, just a way of setting the contrast on the scans, can be useful to assess the bones in people who can’t get an MRI. And then there’s also plain old x-rays, which are also potentially useful in assessing the hips or ribs or other places. They aren’t as clear as an MRI, but they can sometimes provide the added information you need and are certainly widely available and a lot less expensive.

Even with additional studies, sometimes it’s not possible to say definitively whether abnormal areas on these scans are cancer or benign musculoskeletal disease. Occasionally, we need to recommend that patients undergo a biopsy to confirm or exclude bone metastasis. That wouldn’t be widely recommended in most situations in which a patient already has advanced lung cancer, since it’s not as likely to dramatically change treatment plans or prognosis, but in patients who are being staged and may be candidates for surgery and/or aggressive chemo/radiation plans for earlier stage disease, it often makes sense to pursue such a challenging approach only if it wouldn’t be proved futile by progression of metastatic disease in the forseeable future.

I’ll talk about various treatment approaches for bone metastases in some upcoming posts.