Sacral chordoma is a rare, slow-growing type of bone cancer that affects the sacrum, the triangular bone at the base of the spine, commonly known as the tailbone. This tumor is locally aggressive, meaning it tends to grow into nearby tissues and structures, though it may take years before it spreads to distant parts of the body. The unique origin and location of this tumor present specific challenges for both diagnosis and treatment.
Understanding Sacral Chordoma
Sacral chordoma is a very uncommon diagnosis, accounting for approximately 1% to 4% of all primary bone tumors. Despite its overall rarity, it is the most frequently occurring primary malignant tumor found specifically in the sacrum. The tumor originates from remnants of the notochord, which is an embryonic structure that normally disappears early in development. Small portions of the notochord remain in the nucleus pulposus of the spinal discs.
These leftover notochordal cells can undergo malignant transformation, leading to a chordoma, which typically occurs along the midline of the spine. The sacrum and coccyx are the most common sites, representing about 50% of all chordoma cases. Patients are most frequently diagnosed in their 50s and 60s, and the condition affects males more often than females.
The slow-growing nature of the tumor often allows it to reach a significant size before symptoms prompt a medical evaluation. This prolonged growth pattern contributes to the difficulty of achieving a successful treatment outcome later on. The tumor’s cellular structure is distinct, characterized by physaliferous cells, which are vacuolated or “foamy” cells, a feature identified during a biopsy.
Identifying Symptoms and Diagnosis
The symptoms associated with sacral chordoma arise primarily from the tumor pressing on surrounding nerves and structures within the pelvis. The most common initial symptom is persistent pain in the lower back or coccyx area, which often worsens when sitting. This pain typically does not respond well to typical pain medications. As the tumor expands, it begins to affect the delicate network of nerves that exit the lower spine, leading to neurological issues.
Patients may experience numbness, tingling, or weakness that radiates down one or both legs due to compression of the sciatic nerve or other nerve roots. A significant symptom is a change in bladder or bowel function, such as constipation, urinary difficulties, or even incontinence. These issues occur when the tumor affects the sacral nerves controlling these functions. In more advanced cases, the tumor may be palpable as a mass during a physical or rectal examination.
Diagnosis relies on a combination of advanced imaging and tissue analysis. Magnetic Resonance Imaging (MRI) is the preferred initial imaging technique because it provides clear detail of the tumor’s size, soft tissue involvement, and its relationship to nearby nerves. A Computed Tomography (CT) scan is also used to assess the extent of bone destruction caused by the tumor and to detect any distant spread.
The definitive confirmation of sacral chordoma requires a biopsy, where a small tissue sample is removed for microscopic examination by a pathologist. This procedure is typically guided by imaging, such as a CT scan, to ensure accuracy and minimize the risk of tumor cells spreading along the needle tract, a complication known as “seeding”. Pathologists look for the characteristic physaliferous cells. They also test for the presence of the protein brachyury, which is highly elevated in nearly all chordomas, confirming the diagnosis and distinguishing it from other bone cancers.
Primary Treatment Approaches
The primary goal in treating sacral chordoma is to achieve local control of the tumor through two main modalities: surgery and specialized radiation therapy. Successful treatment requires a multidisciplinary team of orthopedic oncologists, neurosurgeons, and radiation oncologists. The treatment strategy is carefully individualized based on the tumor’s size, exact location, and whether complete removal is possible.
Surgery remains the most effective treatment, offering the best chance for long-term survival. The procedure involves an en bloc resection, meaning the entire tumor is removed in one piece with a wide margin of healthy surrounding tissue. This complete removal is critical because even microscopic amounts of residual tumor significantly increase the risk of local recurrence, which is a major challenge with this cancer.
Achieving a clean margin is complicated by the sacrum’s location, which is tightly packed with major nerves, blood vessels, and the bowel. Surgeons must balance the need for a wide margin against the necessity of preserving neurological function. Resection of sacral nerve roots, particularly S2 and below, can lead to functional deficits, including loss of bladder, bowel, and sexual function.
Radiation therapy is used as a complementary or definitive treatment, depending on surgical feasibility and outcome. Chordomas are relatively resistant to conventional photon-based radiation, necessitating the use of high-dose, highly focused techniques. Specialized treatments like Proton Beam Therapy or Carbon Ion Therapy are preferred because they deliver a high radiation dose directly to the tumor while sparing surrounding healthy tissues.
High-dose radiation is often used in an adjuvant setting following surgery, especially if the surgical margins were not completely clear of cancer cells. For patients whose tumors are deemed inoperable due to size or proximity to critical structures, these advanced radiation techniques can be used as the primary, definitive treatment. The precise targeting ability of proton therapy makes it superior for tumors near dose-sensitive organs.
Monitoring and Prognosis
Long-term management of sacral chordoma centers on rigorous monitoring due to the tumor’s high propensity for local recurrence, even years after treatment. Follow-up care involves regular imaging, typically using MRI scans, to detect any signs of tumor regrowth as early as possible. In the first year after treatment, scans may be scheduled every three months, with the interval gradually lengthening over time.
Regular follow-up also addresses potential long-term side effects resulting from the aggressive nature of the treatment. Patients who undergo extensive sacral resection or high-dose radiation may require ongoing rehabilitation and management for chronic issues. These issues include neuropathic pain, motor weakness, and persistent bowel or bladder dysfunction. A dedicated rehabilitation team helps patients adapt and manage these functional changes to improve their quality of life.
Prognosis is highly variable and depends significantly on the initial surgical outcome. Achieving clear, tumor-free surgical margins is the single most important factor influencing local recurrence and long-term survival. Five-year overall survival rates range from approximately 50% to over 70%, with the highest rates achieved after complete surgical removal. The tumor is slow to metastasize, but it can spread to distant sites, such as the lungs and liver, complicating the long-term outlook.