Bone tumor

Primary tumors of bone can be divided into benign tumors and cancers. Common benign bone tumors may be neoplastic, developmental, traumatic, infectious, or inflammatory in etiology. Some benign tumors are not true neoplasms, but rather, represent hamartomas, namely the osteochondroma. The most common locations for many primary tumors, both benign and malignant include the distal femur and proximal tibia (around the knee joint). Examples of benign bone tumors include osteoma, osteoid osteoma, osteochondroma, osteoblastoma, enchondroma, giant cell tumor of bone and aneurysmal bone cyst.

Malignant primary bone tumors, known as bone sarcomas, include osteosarcoma, chondrosarcoma, Ewing sarcoma, fibrosarcoma, and other types. While malignant fibrous histiocytoma (MFH) - now generally called "pleomorphic undifferentiated sarcoma" - primary in bone is known to occur occasionally,^[9] current paradigms tend to consider MFH a wastebasket diagnosis, and the current trend is toward using specialized studies (i.e. genetic and immunohistochemical tests) to classify these undifferentiated tumors into other tumor classes. Multiple myeloma is a hematologic cancer, originating in the bone marrow, which also frequently presents as one or more bone lesions.^[10]

Germ cell tumors, including teratoma, often present and originate in the midline of the sacrum, coccyx, or both. These sacrococcygeal teratomas are often relatively amenable to treatment.^[11]

Secondary bone tumors are metastaticlesions which have spread from other organs, most commonly carcinomas of the breast, lung, and prostate. Rarely, primary bone malignancies such as osteosarcoma may also spread to other bones.^[12] Reliable and valid statistics on the incidence, prevalence, and mortality of malignant bone tumours are difficult to come by, particularly in older adults (those over 75 years of age) - because carcinomas that are widely metastatic to bone are rarely ever curable. Biopsies to determine the origin of the tumour in cases like this are rarely done.

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  Stage 1A bone cancer
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  Stage 1B bone cancer
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  Stage 2A bone cancer
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  Stage 2B bone cancer
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  Stage 3 bone cancer

Chemotherapy and radiotherapy are effective in some tumors (such as Ewing's sarcoma) but less so in others (such as chondrosarcoma).^[15] There is a variety of chemotherapy treatment protocols for bone tumors. The protocol with the best-reported survival in children and adults is an intra-arterial protocol where tumor response is tracked by serial arteriogram. When tumor response has reached >90% necrosis surgical intervention is planned.^[16][17]

One of the major concerns is bone density and bone loss. Non-hormonal bisphosphonates increase bone strength and are available as once-a-week prescription pills. Strontium-89 chloride is an intravenous medication given to help with the pain and can be given in three-month intervals.

Treatment for some bone cancers may involve surgery, such as limb amputation, or limb sparing surgery (often in combination with chemotherapy and radiation therapy). Limb sparing surgery, or limb salvage surgery, means the limb is spared from amputation. Instead of amputation, the affected bone is removed and replaced in one of two ways: (a) bone graft, in which bone is taken from elsewhere on the body or (b) artificial bone is put in. In upper leg surgeries, limb salvage prostheses are available.

There are other joint preservation surgical reconstruction options, including allograft, tumor-devitalized autograft, vascularized fibula graft, distraction osteogenesis, and custom-made implants.^[18] An analysis of massive knee replacements after resection of primary bone tumours showed patients did not score as highly on the Musculoskeletal Tumour Society Score and Knee Society Score as patients who had undergone intra-articular resection.^[19]

Over the past two decades, CT guided radiofrequency ablation has emerged as a less invasive alternative to surgical resection in the care of benign bone tumors, most notably osteoid osteomas. In this technique, which can be performed under conscious sedation, a RF probe is introduced into the tumor nidus through a cannulated needle under CT guidance and heat is applied locally to destroy tumor cells. Since the procedure was first introduced for the treatment of osteoid osteomas in the early 1990s,^[20] it has been shown in numerous studies to be less invasive and expensive, to result in less bone destruction and to have equivalent safety and efficacy to surgical techniques, with 66 to 96% of patients reporting freedom from symptoms.^[21][22][23] While initial success rates with RFA are high, symptom recurrence after RFA treatment has been reported, with some studies demonstrating a recurrence rate similar to that of surgical treatment.^[24]

Thermal ablation techniques are also increasingly being used in the palliative treatment of painful metastatic bone disease. Currently, external beam radiation therapy is the standard of care for patients with localized bone pain due to metastatic disease. Although the majority of patients experience complete or partial relief of pain following radiation therapy, the effect is not immediate and has been shown in some studies to be transient in more than half of patients.^[25] For patients who are not eligible or do not respond to traditional therapies ( i.e. radiation therapy, chemotherapy, palliative surgery, bisphosphonates or analgesic medications), thermal ablation techniques have been explored as alternatives for pain reduction. Several multi-center clinical trials studying the efficacy of RFA in the treatment of moderate to severe pain in patients with metastatic bone disease have shown significant decreases in patient reported pain after treatment.^[26][27] These studies are limited however to patients with one or two metastatic sites; pain from multiple tumors can be difficult to localize for directed therapy. More recently, cryoablation has also been explored as a potentially effective alternative as the area of destruction created by this technique can be monitored more effectively by CT than RFA, a potential advantage when treating tumors adjacent to critical structures.^[28]