What is the most common bone tumor?

Introduction

Osteosarcoma is the most frequently occurring primary bone tumor, with approximately 800-900 new cases diagnosed each year in the United States. It is highly malignant with a tendency to metastasize. Osteosarcoma predominantly affects children and young adults when bones are growing rapidly near the ends of long bones, though a second peak incidence occurs in adults over 65 years of age. If diagnosed early, the outlook for osteosarcoma is more promising than in decades past, however, it remains a serious cancer requiring intensive treatment. Osteosarcoma is a type of bone cancer, so consulting an orthopedist oncologist who specializes specifically in bone tumors is advised.

Symptoms Symptoms of osteosarcoma include:

• Localized bone pain: One of the initial symptoms is localized pain where the tumor occurs, typically in the large bones of the arm near the shoulder or leg near the knee. At first, osteosarcoma pain may only occur at nighttime but typically progresses over time to become constant. The pain may get worse with activity.
• Swelling/Mass: As the tumor eats away bone tissue, it progresses outward into surrounding soft tissue. This manifests as noticeable swelling circumferentially around the limb where it has originated. Eventually, as the swelling grows, a palpable mass may be felt depending on tumor size and location.
• Fractures: The tumor may weaken the bone it develops within, causing pathologic fracture with minor trauma that would not usually cause breakage. Suspected stress fractures not improving with conservative care may also lead to asking further questions.

Causes and Risk Factors

The exact cause of osteogenic sarcoma is unknown, but various factors can increase one’s risk of development:

• Age: The first peak incidence occurs in adolescence during rapid bone growth. Osteosarcoma proliferation seems to begin with errors in replicating DNA to make new osteoblast bone cells. A second peak occurs later in life.
• Growth Spurts: Rapid bone growth in unusually tall individuals going through growth spurts may predispose cells toward malignant changes. The longer bones grow, the more chance issues can develop. Those with taller adult height seem at higher risk. Variants in genes regulating height and growth may play a role.
• Radiation Exposure: Particularly in previously treated radiotherapy fields, damage to osteoblasts from ionizing radiation exposure seems capable of later causing chromosome errors that result in bone cancer.
• Genetic Conditions: Certain genetic disorders substantially increase osteosarcoma risk including Li-Fraumeni syndrome, Rothmund-Thomson syndrome, Bloom syndrome, Werner syndrome, and hereditary retinoblastoma among others. Evaluating children of cancer survivors seems prudent.
• Previous Chemotherapy: Certain drugs used to treat other cancer types (alkylating agents, topoisomerase inhibitors) heighten secondary osteosarcoma occurrence probability. The mechanism relates to the ability of these agents to break chromosomal strands.

Diagnosis

A combination of imaging tests and biopsy will facilitate an osteosarcoma diagnosis:

Imaging Tests

• X-rays detect radiolucent bone destruction and mineralized bone-forming tumor matrix. It can also reveal any tumor-related sunburst pattern of speculations or Codman’s triangle from periosteal elevation.
• CT scanning gives a higher resolution three-dimensional view allowing detailed pre-surgical assessment of tumor size, location, extension into soft tissues, and skip metastases presence.
• MRI scanning excels at evaluating medullary content and the extent of soft tissue mass in the tumor; it is the preferred modality for mapping relative to neurovascular structures for surgery planning.

Biopsy

Microscopic tissue examination confirms diagnosis since inconsistent bone anatomy or imaging artifacts occasionally result in misdiagnosis. Routinely two types of biopsy are completed:

1. Core Needle Biopsy: Multiple samples are obtained under imaging guidance using a hollow, core sampling needle inserted through soft tissues and into the tumor itself.
2. Open Surgical Biopsy: Once imaging localizes the tumor, surgeons take multiple small but deeper incisional wedge biopsy samples using a larger needle or forceps directly from the tumor and surrounding tissues. This procedural approach has fallen from favor due to potential contamination risk.

Three Things are Evaluated Histologically:

1. Tumor necrosis percentage
2. Mitotic activity
3. Tumor differentiation staging

These prognostic criteria can be combined with anatomical staging and histological class grading. Cytogenetic and molecular studies also guide treatment selection and outcome prediction.

Treatments

Modern standard treatments for osteosarcoma include:

• Neoadjuvant & Adjuvant Chemotherapy: Utilized before and after surgery, chemotherapy uses chemicals to target and kill systemic micrometastatic cancer cells circulating to the lungs or elsewhere. Regimens combine methotrexate plus other augmentative or alternating drugs for maximum survival benefit.
• Definitive Surgery: Whenever feasible, total gross tumor resection surgery occurs next – usually at week 10-12 once initial chemotherapy shrinks the soft tissue component for salvageability. Surgeons remove the entire tumor as a cylindrical segmental bone defect, replacing the missing section with cadaver bone, an autograft, implanted metal, or a composite prosthesis. With poor response, amputation may still be required. Follow-up is intense.
• Radiation Therapy: While previously avoided due to effects on bone growth, charged particle beam or proton beam radiotherapy now allows high-dose localized ablation with reduced field sizes to destroy remaining tumor cells usually displaced during medical treatment or surgery. Stereotactic approaches ensure accuracy.

Improved understanding of osteosarcoma at the molecular level may soon help optimize and customize treatment. Targeted biological agents could supplement chemotherapy drugs of the past that merely attacked all rapidly dividing cells. Gene sequencing early on also guides what second agents to transition toward in relapsed disease.

Outlook

Survival rates by stage for osteosarcoma are as follows:

• Localized Tumor: Around 70% now survive long-term if the mass has not yet spread.
• Metastatic Tumor: Only about 30% will achieve lasting remission if metastasis already occurred with a poorer prognosis when outside the lungs or pleural cavity at diagnosis.

Early diagnosis, specialized treatment at oncology hospitals with the best orthopedic doctor, clinical trial participation, and postoperative monitoring for recurrence are vital to combat osteosarcoma’s tendency for aggressive growth and metastasis formation. Counseling can provide children and parents guidance when faced with this disruptive bone cancer before, during, and after therapy. Support groups ease isolation and provide networking for funding assistance concerns beyond insurance.