Osteosarcoma is a rare bone cancer originating in cells that form new bone tissue. It often develops in the long bones of the arms and legs, especially around the knee. When this cancer spreads beyond its initial site to other body parts, it is called metastatic osteosarcoma. This indicates a more advanced stage, increasing complexities for diagnosis and treatment.
What Metastatic Osteosarcoma Means
Metastasis occurs when cancer cells detach from the primary tumor and travel through the bloodstream to establish new tumors in distant sites. For osteosarcoma, cells invade surrounding tissues, enter the circulatory system, and colonize new locations.
The lungs are the most frequent site for osteosarcoma to spread, occurring in approximately 80% of metastatic cases. Other bones are also common sites, appearing in 10% to 30% of patients at diagnosis. Less common sites include the brain, lymph nodes, and various soft tissues and organs like the heart, kidney, liver, and pancreas. The presence of metastatic disease at diagnosis often leads to a less favorable prognosis compared to localized disease.
Identifying Metastasis
Detecting metastatic osteosarcoma involves imaging techniques and, sometimes, biopsies. Initial evaluation often includes plain radiographs, but more detailed imaging is required for comprehensive assessment. These advanced methods visualize the tumor’s extent and identify any spread.
Computed tomography (CT) scans are used to identify metastatic lesions, especially in the lungs. A chest CT scan is more sensitive than a standard chest X-ray for detecting small lung nodules. CT scans also help define the primary tumor’s extent within the bone and surrounding soft tissues.
Magnetic resonance imaging (MRI) provides detailed images of soft tissues and bone marrow. It is effective for assessing the primary tumor’s extent, including spread within the bone and into adjacent soft tissues. MRI can also detect “skip metastases,” which are small, separate tumors in the same bone but distant from the main tumor. Whole-body MRI is highly sensitive for identifying skip metastases and other distant spread.
Bone scans use a small amount of radioactive material to detect cancer spread to other bones. Areas of increased bone activity, called “hot spots,” can indicate metastatic lesions. Positron Emission Tomography (PET) scans, often combined with CT (PET/CT), use a radioactive sugar absorbed by rapidly growing cancer cells. PET/CT provides a whole-body view, showing osteosarcoma spread to the lungs, other bones, or organs, and helps assess treatment response.
While imaging tests suggest osteosarcoma or its spread, a biopsy is the only definitive way to confirm diagnosis and tumor grade. This involves removing a small tissue sample for microscopic examination. If metastases are present at diagnosis, these sites may also be biopsied to confirm cancer cells.
Comprehensive Treatment Strategies
Treating metastatic osteosarcoma requires a multi-modal approach to target the disease effectively. The primary goal is to remove or control both the original tumor and any metastatic sites. This often involves a sequenced combination of systemic therapy and local treatments.
Chemotherapy is a primary treatment, typically involving drugs like high-dose methotrexate, doxorubicin, and cisplatin (the “MAP” regimen). This systemic treatment is usually administered before surgery (neoadjuvant chemotherapy) to shrink the primary tumor and visible metastases. It is also given after surgery (adjuvant chemotherapy) to eliminate remaining cancer cells. While chemotherapy has improved survival rates, its effectiveness can be more limited in patients with metastatic disease at diagnosis compared to those with localized tumors.
Surgical removal of the primary tumor is a standard procedure, with limb-sparing surgery often an option. This involves removing the tumor with a margin of healthy tissue and replacing the bone with a graft or prosthesis. For metastatic lesions, especially in the lungs, surgical removal (metastasectomy) is often pursued if tumors are resectable. The ability to surgically remove all metastatic sites is a significant factor in improving outcomes.
Radiation therapy plays a limited role compared to chemotherapy and surgery, as osteosarcoma cells can be resistant. However, it can be used when a tumor cannot be completely removed by surgery, or for pain control and local management of unresectable lesions. Advanced techniques like stereotactic body radiation therapy (SBRT) are being explored for recurrent or metastatic osteosarcoma, showing promise in targeting tumors with high precision.
Emerging therapies and clinical trials are exploring new avenues to improve outcomes. These include high-dose chemotherapy with autologous stem cell transplantation, which allows for more intensive chemotherapy by rescuing healthy blood-producing cells. Immunotherapies and molecularly targeted drugs, which specifically attack cancer cells based on their unique biological characteristics, are also under investigation. A multidisciplinary team, including oncologists, surgeons, and radiation oncologists, typically develops the treatment plan.
Outlook and Supportive Care
The outlook for metastatic osteosarcoma remains challenging. Historical survival rates for widespread disease were less than 20%. However, chemotherapy advancements have improved outcomes, with some studies reporting 5-year overall survival rates ranging from 10% to 40%. Prognosis varies depending on factors like the number and location of metastases, the primary tumor’s response to chemotherapy, and if all visible cancer can be surgically removed. Patients with lung metastases, especially those with fewer nodules and successful surgical removal, tend to have a better prognosis than those with more widespread or extrapulmonary metastases.
Supportive care is an integral component of managing metastatic osteosarcoma, focusing on improving the patient’s quality of life. This comprehensive approach addresses physical symptoms and the emotional and psychological well-being of patients and their families. Pain management is a significant aspect, as osteosarcoma can cause considerable pain due to tumor growth or treatment side effects.
Pain relief strategies include non-opioid drugs for mild pain and stronger opioids for moderate to severe pain. Radiation therapy can also be used for palliative pain control by slowing tumor growth. Innovative techniques like MRI-guided focused ultrasound (MRgFUS) are being explored for non-invasive pain relief by ablating tumor tissue and deadening pain-sensing nerves.
Psychosocial support for patients and their families is also a high priority. Dealing with a cancer diagnosis, especially one that has spread, can be emotionally taxing. Support groups, counseling, and psychological interventions help patients cope with anxiety, depression, and post-traumatic stress symptoms. Many organizations offer resources and peer support to navigate these emotional challenges.