I. General Information about Tumors
A tumor is simply an abnormal growth and often times the cause is not known. It is a collection of cells that are clones from an original cell that grew uncontrollably. In most cases this does not occur because of careful checks and balances within the body. The actual cell of origin (i.e. bone, muscle, fat, nerves, etc.) will often determine the nature and behavior of the tumor. A tumor can be benign or malignant (cancerous). A benign tumor is not a cancer and rarely is life-threatening. A malignant tumor is a cancer and can spread throughout the body. These cells have the ability to enter the blood / lymph system and spread to distant sites. Their biology varies but all have the ability to be life-threatening. It is suggested that a combination of genetic, acquired and environmental influences predispose us to tumor formation.
II. Types of Bone Cancer
Bone cancer can either be primary (sarcomas) or secondary (metastatic). Primary implies the tumor is derived from the bone itself whereas secondary suggests it is from another site and spread to the bone (ie. Metastatic bone disease / cancer). The most common sources of metastatic bone cancer are:
- Breast (2) Lung (3) Thyroid (4) Kidney (5) Prostate
(These are considered carcinomas)
Approximately 12-13,000 people are diagnosed with a sarcoma each year in the United States and of these only 2,500 are of the bone. This is dramatically less than the number of patients diagnosed with metastatic bone cancer. About 1.2 million people are diagnosed with cancer annually and it is predicted that half will develop metastatic disease.
Other forms of bone cancer exist such as multiple myeloma and lymphoma. These forms are generally systemic diseases and only need surgical intervention if chemotherapy and / or radiation is not effective in controlling pain or if the bones are at risk of fracture.
III. What is a Sarcoma and Carcinoma?
Sarcomas are cancers that derive from mesodermal cells (bone, muscle, fat, etc.). They often have a predictable growth pattern and usually appear “ball-like” and normally push adjacent anatomical structures out of the way. These cancers can metastasize and this most commonly occurs to the lungs and less commonly to other bones, the liver and rarely the lymph nodes. The tendency of distant spread is based on the grade which is determined by a pathologist after a thorough microscopic review of a biopsy. Generally, the higher the grade, the more aggressive the cancer. Depending on a variety of factors, soft tissue and bone sarcomas are treated differently. For example, chemotherapy is used for many pediatric high-grade sarcomas but this is significantly less common in the adult. Surgery is almost always necessary, however radiation has specific indications.
Carcinomas as mentioned above are another group of cancers that can be found within bone but originate from another site. They behave in a different manner and typically violate normal anatomic boundaries. They are infiltrative and can spread essentially anywhere. This makes them more difficult to remove surgically. Many of these require chemotherapy and radiation.
IV. What is Chemotherapy and How does it Work?
Chemotherapy is a description of a variety of toxic medications that provide systemic treatment against cancer. There are different mechanisms of action however they all try to achieve the same goal, which is to kill cancer cells. Unfortunately, the drugs are not particularly selective and often target good and bad cells. The response is often based on growth and tissue type. The side effects that are most common are attributable to organs and tissues with rapid turnover. As a result, diarrhea and hair loss are frequently noted since the gastrointestinal tract and the scalp are metabolically active and often producing new cells. For some sarcomas, neoadjuvant chemotherapy (preoperative chemotherapy = induction chemotherapy) is used to kill the tumor, make it smaller, and facilitate removal. In addition, it is employed as a systemic treatment to eliminate microscopic disease throughout the body. In a similar way, adjuvant chemotherapy (postoperative chemotherapy) is often used to eradicate any microscopic residual disease. The medications used are determined by a medical or pediatric oncologist who works intimately with the multi-disciplinary team. In some instances, patients are enrolled in national chemotherapy protocols / trials which may provide the most advanced but at times experimental treatments if they meet criteria.
V. What is Radiation and How does it Work?
Radiation is simply a method of local tumor control. It can be administered in several ways. The most common is external beam radiation which is a technique for delivering a beam of high-energy x-rays to a tumor. The x-rays are generated outside the patient often in a linear accelerator and is specifically targeted at the tumor site. Its goal is to kill tumor cells but requires careful treatment planning to spare the surrounding normal tissues. The treatment is administered by a radiation oncologist. The process is divided into three main parts: (1) simulation (2) treatment planning (3) treatment delivery. The treatments are painless, however depending on the dose and the patient, the side effects vary. These include problems such as stiffness, scarring, burns, lymphedema / swelling, muscle atrophy and contractures, radiation induced cancers, fracture, nerve damage and pain. External beam radiation can be used before or after sarcoma resection if indicated. It is infrequently used for bone sarcomas unless the tumor cannot be removed surgically but commonly for soft tissue sarcomas. There are advantages and disadvantages. Other options exist including tomotherapy, Cyberknife, and brachytherapy which may play a role in very select cases.
VI. Do I Need Surgery and What Options are There?
The need for surgery for musculoskeletal tumors is based on the diagnosis. Some benign lesions can be treated conservatively with careful observation and repeat radiographic studies. However, benign but aggressive tumors normally need surgery which (if appropriate) can be done by a curettage (“scraping or scooping out”) procedure. This is often done in conjunction with burring the cavity and using a form of adjuvant such as an Argon beam coagulator (laser-type, plasma) device. The bone often needs to be reinforced with graft, bone cement, or hardware (plate, screws, rods, etc).
Both soft tissue and bone sarcomas are usually removed surgically. Over 90 percent of patients can have a limb sparing operation (surgery that preserves the limb rather than amputation). The advances in chemotherapy, reconstructive options and surgical technique have pushed the envelope in terms of available surgical choices. Portions or entire bones including the joints can now be replaced quite effectively. The overall goal is to remove all of the cancer but provide as close to normal function as possible.
Metastatic bone disease can be treated in many ways. Over the past several decades patients with cancer that has spread to the bone have lived longer. As a result, the surgical options vary from simply reinforcing a bone that is at risk for fracture versus complete resection of the bone with endoprosthetic (metallic implant) reconstruction. These procedures are quite effective in reducing pain and providing a better quality of life. Often times the surgery chosen is directly related to the risks and benefits as well as the overall prognosis. This is determined by careful planning between the musculoskeletal oncologist, medical oncologist and radiation oncologist.