About 300 new cases of osteosarcoma are diagnosed each year in the United States. This disease occurs more often in boys than in girls, usually arising in areas of rapid bone growth. Therefore it is most likely to occur during the growth spurt of puberty and at the sites of especially rapid growth, such as the ends of the leg bones, upper arms, and hips.
Typically, the disease may be brought to a parent’s attention by a child’s complaints of persistent pain after a relatively minor injury, such as a fall or bad bruising. X rays show an enlargement near the growing end of the bone, with areas of excessive new bone formation and destruction. The layer of tissue that surrounds and protects normal bone (the periosteum) is elevated by the tumor growth, producing bony spines at right angles to the main bone shaft, creating a so-called sunburst appearance.
The cancer frequently spreads, usually to the lungs. It rarely metastasizes to the lymph nodes, the common route of spread in many other types of cancer. After involving the lungs, the cancer cells occasionally spread to other bones and soft tissues.
In the past, spread of the cancer to the lungs became apparent within six months in 50 percent and within a year in 80 percent of patients with osteosarcoma. This occurred despite early amputation of the affected limb, leading the assumption that undetected microscopic spread of the cancer to the lungs was probably present in at least 80 percent of the patients at the time of initial diagnosis. Before the use of chemotherapy, the expected cure rate with amputation alone was only about 10 to 20 percent. Because of this bleak outlook, radiation therapy was at one time used as the initial means of treatment, with the intent to avoid amputation in patients who were probably going to die from their lung metastases.
Following this logic, the primary bone tumor was irradiated and amputation was performed only if the patient did not appear to have lung metastases within four to six months.
As a result of this treatment strategy, some patients could occasionally avoid amputation if local irradiation of the bone tumor produced good results. Very often, however, cancer spread occurred during (or before) the radiation therapy and amputation had to be performed later to relieve suffering and prolong life as much as possible. Thus, amputation remained a standard form of treatment.
Recent advances have markedly improved the overall survival rate and changed the approach to treatment, again demonstrating the giant steps forward that have been made in cancer therapy in recent years. Today’s typical treatment involves surgical removal of the primary tumor, followed by chemotherapy to destroy the microscopic lung metastases that remain despite surgical treatment in more than 80 percent of osteosarcoma patients.
The dramatic change in the outlook for osteosarcoma began in the 1970s with the discovery that several chemotherapeutic agents were effective. (These include such potent anticancer drugs as methotrexate with citrovorum factor, adriamycin, cisplatin and cyclophosphamide.) Chemotherapy has now been used for about a decade and has produced survival rates of about 70 to 90 percent.
There is some dispute, however, over whether this improved survival can be totally credited to the addition of chemotherapy to the treatment regimen. Researchers at the Mayo Clinic, for example, contend that there has been a “natural” increase in survival that cannot be attributed entirely to chemotherapy. Be that as it may, the fact that a number of anticancer drugs are effective in treating osteosarcoma is not disputed, and this has prompted studies to determine whether chemotherapy alone can be used to treat the primary tumor as well as the lung metastases, thereby avoiding amputation.
This treatment plan, known as “limb salvage,” is being investigated at several leading cancer centers in the United States. It involves the administration of anticancer drugs before surgery. In the subsequent operation, only the tumor itself (rather than the entire limb) is removed, and a metal bone prosthesis is inserted.
In some instances in which the tumor is extremely small, the preoperative chemotherapy may be eliminated. Following the removal of the tumor, most patients continue to receive chemotherapy for varying periods of time. This approach is still experimental and is being tried on only a small number of patients. Selection is based on age, the potential for surgical removal of the tumor without resorting to amputation, and the attainment of maximum growth in patients with cancers of the lower limbs.
This method of experimental treatment follows the guideline that any new therapy must be expected to be at least as effective as present therapies, if not more so, and should be tried in only a small group of closely monitored patients in order to produce a clear conclusion as to its efficacy and possible advantages.
In addition, at several cancer centers the use of preoperative chemotherapy is being studied in patients about to undergo amputation. These studies are intended to determine, by actually observing the effects of preoperative drugs on tissues that are later removed, whether a chemo-therapeutic regimen designed to treat the primary tumor also works against microscopic disease. This effort is being further enhanced by the recent development of cell culture techniques that permit the testing of various anticancer drugs to measure their effectiveness in a laboratory setting. The technique is similar to that used in laboratory tests to determine which antibiotics should be used to treat a particular bacterial infection.
Although spread of the cancer to distant organs is still very common in osteosarcoma, it should be emphasized that the outlook for patients with this disease has improved dramatically in recent years. With the current highly effective multidrug regimen, cures are being achieved in patients who would have been considered hopeless just a few years ago. Therefore a diagnosis of metastatic disease is no longer a death warrant. Metastases are usually treated with a combination of surgery, drugs and, occasionally, radiation therapy. Overall, a 40 percent cure rate can be expected in patients who even at the initial diagnosis are found to have lung metasta-ses. The cure rate for those patients who later develop metastases to the lung also is steadily improving.
In dealing with osteosarcoma, it should be noted that there are at least three types of the disease, and determining the particular type is important in designing the approach to treatment and judging the probable prognosis. The least malignant type is called parosteal or juxtacortical osteosarcoma. Another closely allied type is designated the periosteal variety. These occur most commonly in the midshafts of the long bones rather than at the growing ends. These particular types are very slow-growing, and any metastases usually occur later in the course of the disease. Treatment generally consists only in the removal of the tumor, although in some cases amputation may be required. The cure rate is about 80 percent, even without adjuvant chemotherapy. In fact, use of chemotherapy in these types of osteo sarcoma is debatable because the drugs themselves involve risks that may outweigh any increased benefit from them. However, this is a situation that varies, and any such judgment should be based on the circumstances of the individual patient.
The second type is known as multifocal osteosarcoma, and, as its name suggests, it occurs in several bones simultaneously, or it may arise in one bone and metastasize to other parts of the skeleton without first involving the lungs. This particular form of osteosarcoma is highly malignant and has a poor prognosis. Treatment is usually the surgical removal of the major tumors and chemotherapy. Radiation therapy also may be used as a palliative measure.A third type is called soft-tissue osteosarcoma because it occurs mostly in the soft tissues. It is treated like conventional osteosarcoma, although its prognosis is not as good. Fortunately this variation of osteosarcoma is extremely rare.