Review of Rare Sacral Tumors
Tumors of the sacrum are rare but can create serious problems. They can be benign or malignant. They may be primary, which means they develop first right in the sacrum. Or they can be the result of local invasion or metastases. Local invasion means they start in a nearby area (like the pelvis or rectum) and spread to surrounding tissues. Metastases refers to the fact that the cancer cells spread from someplace else farther away -- most often the lung, breast, prostate, kidney, gastrointestinal tract, or thyroid.
In this review article, neurosurgeons from Johns Hopkins University bring us up-to-date on the various types of sacral tumors, how to diagnose them, and how to treat them. Tumors anywhere in the body can be classified in different ways. Sacral tumors are put into one of four main groups. Those groups are congenital (present at birth), metastatic (malignant cancer spread from somewhere else in the body), primary osseous (forms first in the bone), or primary neurogenic (forms first in the nerve tissue of the sacrum).
Most of the time, sacral tumors are the result of cancer someplace else in the body. Regardless of where the tumor arises (in the sacrum first or metastasized from elsewhere), the diagnosis is difficult to make and can often be delayed significantly. Symptoms develop slowly.
The patient may experience back and/or buttock pain that seems to get better or worse with certain movements. This type of back pain is referred to as mechanical low back pain. Often the symptoms mimic other less serious back problems. The patient may be treated conservatively with pain relievers. If symptoms persist, they may be referred to a physical therapist. All of this can delay an accurate diagnosis for months to years.
It isn't until the tumor grows large enough to cause additional symptoms such as loss of bowel and/or bladder control or change in deep tendon reflexes that the true nature of the problem is discovered. In other cases, severe, chronic and painful constipation or sexual dysfunction are the first clues to tip the doctor to look more closely at the problem. Sometimes pressure on the nerves in the sacral area causes severe enough pain that the diagnosis is finally made.
Additional diagnostic studies may include X-rays or more advanced imaging such as CT scans, MRIs, and/or bone scans. X-rays are very unreliable for these kinds of tumors. The tumor may not show up -- or other structures in the area can block a clear view of the tumor. That's unfortunate because it can mean the diagnosis is delayed again.
CT scans may be more helpful. Certain features of the tumors may be seen more clearly with this type of imaging because it is more detailed and more sensitive. CT scans are also used to guide needle biopsy, which is used to detect sacral tumors with greater accuracy. The authors discuss when to use needle biopsy and what kinds of risks there are with this type of diagnostic testing. If the results of needle biopsy are unclear, then open biopsy may still be required.
Bone scans are able to show where lesions are present, but they don't answer the question of what are those lesions? A more advanced form of bone scan called SPECT can help tell the difference between benign and metastatic lesions. Some experts advise ordering SPECT scans for anyone suspected of having cancer in the lumbar spine, sacrum, or pelvic areas.
Once the diagnosis has been made, then a plan of care is established. Pain control is the first priority. These tumors can be very large and press on many structures creating intense pain. The location so close to nerves (called the lumbosacral plexus) in the lumbar and sacral areas creates severe nerve pain in the majority of patients.
Pain relievers such as mild analgesics may not be enough. Some patients require opioid therapy (narcotic drugs). Other medications used to control cancer pain include corticosteroids, antidepressants, anticonvulsants, and even indwelling (continuous) nerve blocks.
Surgery to remove the tumor isn't always possible right away. The tumor can be too large or too enmeshed with other structures to remove it easily. Radiation may be used first to shrink as much of the tumor as possible. But even radiotherapy has its limits because the area involved can be large, complex, and difficult to reach.
Newer technology with stereotactic radiosurgery focuses several cross-fired beams of radiation to a single point or smaller area at a time. This helps reduce damage to the surrounding tissue that doesn't need radiation. Computer-controlled robotic spinal radiosurgery is now available. You may have heard of this as it is referred to as CyberKnife treatment. It's not available everywhere, and studies are ongoing but early results are very favorable.
And finally, there's surgery. Tumors that are advanced by the time they are diagnosed make surgery difficult and complex. Removing the tumor, a procedure called resection, isn't always a straightforward process. The anatomy of the pelvic and sacral areas is a challenge. Bowel, bladder, and sexual function are easily disrupted by any changes in this area. The patient's preoperative health can also make a difference (e.g., diabetes, high blood pressure, heart disease).
Some patients just won't be able to have surgery to remove the tumor. For example, this may be the case if the tumor has invaded the spinal cord, nearby organs, or major blood vessels and can't be cut out easily. Or there may be so much bone involved that it's impossible to amputate enough soft tissue and bone to get it all without major disfigurement or loss of function.
Even for those for whom surgery is an option, multiple procedures may be needed to reconstruct vital bowel and bladder structures. Removal of the entire sacrum (called sacrectomy) can be a major undertaking, especially if the sacroiliac joints are compromised by the tumor. This anatomical area provides support, stability, and biomechanical function for the entire lower body.
Some patients will need additional radiotherapy after surgery. Patients who have surgery combined with follow-up radiotherapy have the best outcomes when compared with surgery alone or radiotherapy alone. Measures of outcome are reported in terms of pain levels and ability to walk again. For example, in one study, 84 per cent of the patient who had surgery followed by radiotherapy were able to walk again. Many of those patients were unable to walk before the surgery. This was compared to only 57 per cent who were able to walk having only received radiotherapy.
Great improvements have been made even in the last 10 years in surgical techniques for these kinds of problems. Many patients are able to regain motor function and walk again. Prognosis is good for pain reduction. Disease-free survival is possible but the rates vary with each tumor type. Recurrence can occur, but the incidence of such was not reported in this article.
Daniel M. Sciubba, MD, et al. Diagnosis and Management of Sacral Tumors. In Journal of Neurosurgery: Spine. March 2009. Vol. 10. No. 3. Pp. 244-256.