|Sarcomas of Soft Tissue: The Basics|
|Carolyn Vachani, RN, MSN, AOCN|
|The Abramson Cancer Center of the University of Pennsylvania|
| Last Modified: April 23, 2012
What is sarcoma?
Sarcoma is a cancer of the soft tissue or bone. (This article will discuss soft tissue sarcomas, and sarcomas of the bone will be discussed separately). Soft tissues include muscles, tendons, fibrous tissues, fat, blood vessels, nerves, and synovial tissues (found in joints). Sarcomas are more specifically named by the tissues they affect. For example, sarcoma that arises from the bone is called osteosarcoma (although there are other types that form in the bone), and a sarcoma of the fat cells is called liposarcoma. (See list below for types of soft tissue sarcomas). Soft tissue sarcomas encompass a group of 50 different types of tumors, with most types considered extremely rare. Sarcomas account for less than 1% of all adult cancer diagnoses, with close to 11,000 new cases annually in the soft tissues and 2,800 new cases annually in the bone. Soft tissue sarcomas can develop from any site in the body, but the majority form in the extremities (about 50%), most commonly in the thigh. The remaining cases are evenly distributed throughout the rest of the body (10-15% in the trunk, <10% in the head & neck and 15% in the retroperitoneum).
Am I at risk for sarcoma?
Soft tissue sarcomas (STS) can develop in people of all ages, with approximately 20% of cases in people under age 40, 30% in people from 40-60 years of age, and 50% in people older than 60. In most cases of sarcoma, no specific cause is known. Sarcomas can develop secondary to radiation therapy for another cancer, but these are most often osteosarcomas. There is thought to be an increased risk with exposure to chemicals used in certain industries, but research of these chemicals has produced mixed results, and a clear-cut association has not been found. The agents in question include: phenoxyacetic acids (forestry workers), TCDD (tetrachlorodibenzo-p-dioxin), Agent Orange (Vietnam veterans), chlorophenols (sawmill workers), thorotrast (formerly used as radiology contrast), vinyl chloride, and arsenic (vineyard workers). There is also thought to be a link between chronic lymphedema (induced by surgery, radiation, or congenital abnormalities) and a type of sarcoma called lymphangiosarcoma. Lastly, there are a few genetic syndromes that are linked to STS; these include Li-Fraumeni syndrome, neurofibromatosis, and familial retinoblastoma.
Given the lack of a clear-cut cause, one cannot really prevent sarcoma from developing, aside from maybe avoiding the chemicals listed above.
What screening tests are available?
Unfortunately, there is no screening test for STS. Screening tests are developed for the early detection of common or very deadly diseases. Given how rare STS are, they would be difficult to screen for in the general population. In addition, the number of different types of STS would make it very difficult to develop one single screening test that could detect all types.
What are the signs of Soft Tissue Sarcoma?
The signs of STS are dependent on where the tumor has formed. As the majority of STS form in the extremities, those patients will most likely present with the complaint of a mass or lump found in the extremity, with or without swelling. Depending on its location and size, the mass may or may not cause pain. If the tumor arises in the abdomen, it may reach considerable size before it is detected or leads to abdominal or back pain. Tumors arising in the gastrointestinal tract may cause diarrhea, constipation, blood in the stool, or abdominal pain. A uterine sarcoma may cause bleeding, swelling, or pain in the pelvic area.
How are Soft Tissue Sarcomas diagnosed and staged?
In general, blood tests are normal in patients with STS. Initial imaging studies depend on the location of the tumor. For STS located in the extremities or in the pelvic region, magnetic resonance imaging (MRI) is the study of choice. For STS located in the abdomen, CT scan is the preferred study.
Given how rare sarcomas are, many physicians have never seen or cared for a patient with sarcoma. When sarcoma is suspected, it is important to seek out a physician team familiar with sarcoma. A biopsy is critical for diagnosis and to determine the exact type of sarcoma. Successful biopsy requires knowledge of sarcomas and their treatment, and is best done by a surgeon familiar with sarcoma, followed by examination of the sample by a pathologist who has experience with sarcoma specimens. Biopsies can be performed as an open (surgical) procedure or a closed (percutaneous) procedure (using a large needle to remove the tissue). The biopsy must be performed properly to collect enough tissue to get a diagnosis, but not so much tissue that it would compromise the definitive surgical treatment of the tumor. In general, the preferred method is the least invasive technique required that still allows the pathologist to give a definitive diagnosis.
Most tumor types are staged using a system developed by experts, but this has been difficult to develop for STS given the number of types and the varying locations. The most widely used system has been developed by the American Joint Committee on Cancer (AJCC) (7th edition). It incorporates tumor size, histologic grade (how different the cells look under the microscope when compared to normal cells) and spread to lymph nodes or other body sites in determining the stage.
These are then combined to give a stage:
In addition to official staging, doctors consider a few characteristics that point to a higher likelihood of relapse when deciding on treatment options. Patients with these characteristics are considered "high risk" and may be treated more aggressively. Some high-risk factors include: high grade (appearance under the microscope), deep location, size > 10cm, age > 50, or presenting with a recurrence in the area of the original tumor. CT scan of the lungs may be performed to assess for spread of the tumor to the lungs, as this is the most common place to which STS metastasize (spread). If the particular tumor type can spread to bone, a bone scan may also be performed to look for metastasis.
How is Soft Tissue Sarcoma treated?
Given the rarity of STS, these patients are best served at a specialty treatment center. A Swedish study demonstrated that local recurrence rates were 2 and a half times higher in patients not referred to specialty centers. The study also found worse outcomes in patients who were referred to specialty centers after their initial surgery. Treatment of STS requires complex multi-modality therapy (surgery, radiation and chemotherapy). Specific treatment is dependent upon the size and location of the tumor, the grade (aggressiveness) of the tumor, and whether or not it has spread. The following is a general review of current treatments, but specific cases should be discussed with the doctors on the team.
Surgery is the primary means of treatment in STS, with the goal of complete tumor removal. Unfortunately, given that most tumors arise in the extremities, this can mean amputation of the affected limb. Through great surgical advances and the use of radiation therapy after surgery, only 10% of patients require amputation today, an overwhelming improvement from previous years. In addition to the tumor, the surgeon typically removes a 2-cm area of normal tissue around the tumor whenever possible. There is a low risk of spread to lymph nodes, therefore lymph node dissection is not routinely performed. However, in certain subtypes, lymph node involvement is more common (angiosarcoma, embryonal rhabdomyosarcoma). In these patients, if lymph node involvement is suspected, removal of these nodes can be curative. For patients with small, low risk tumors, surgery can be curative. However, most patients will also require radiation therapy.
Radiation therapy can be performed before or after surgery, or during surgery through the use of brachytherapy. Studies have clearly shown that treatment with radiation prevents recurrence in the area of the original tumor more so than surgery alone. In addition, radiation in conjunction with limb-sparing surgery allows patients with STS in an extremity to avoid amputation. One question researchers have not been able to confirm is whether this prevention of local recurrence actually improves overall survival rates.
In addition, there is no consensus on when to give radiation to achieve the best outcomes. Pre-operative radiation may allow smaller doses of radiation with smaller, better-defined treatment areas and result in a smaller surgery by shrinking the tumor before surgery. But, preoperative radiation can make precise staging more difficult and can result in poorer wound healing after surgery. One Canadian study, comparing pre and post operative radiation, found tumor recurrence and survival to be equivalent, with some differences in side effects.
In the last 30 years, significant improvements have been made in surgical and radiation techniques, improving survival and quality of life for patients with STS. Unfortunately, improvements have not been seen in regards to chemotherapy treatments for STS. Chemotherapy can be given before surgery (called neoadjuvant), in an effort to shrink the tumor enough to allow for a better resection, or after surgery (called adjuvant). Surgery and radiation can only act on a small area around the tumor site, whereas the main goal behind adjuvant chemotherapy is to kill any cancer cells floating undetected elsewhere in the body. It is these cells that can plant themselves and start to grow in other organs, most commonly the lungs.
Seventy five percent of patients will be cured with surgery and radiation alone, so it is important to limit chemotherapy treatment to those patients at highest risk for relapse, as chemotherapy carries with it the downside of significant toxicity. Of the available chemotherapies, only a small handful of drugs have shown any effect on STS. These medications are: doxorubicin, ifosfamide, epirubicin, gemcitabine, and dacarbazine. Although there have not been any large, controlled trials to determine which regimen provides the best outcomes, smaller trials seem to say chemotherapy does provide a benefit for some patients at high risk for recurrence, but is not considered standard of care for all. Each case requires individual consideration based on tumor type, grade, completeness of the surgery (chemotherapy cannot make up for an incomplete surgery) and other predictors of high risk for recurrence.
Clinical trials have been looking at targeted therapies in the treatment of STS, which often contain mutations that may be susceptible to these therapies. This is based on the success of treatment for an STS called gastrointestinal stromal tumors (GIST). This tumor’s prognosis has been transformed since the availability of imatinib, a tyrosine kinase inhibitor. Researchers hope to identify abnormalities in other subtypes of STS and then medications that target these mutations.
Follow Up Care
STS that metastasize generally spread to the lungs first. Researchers have learned that by surgically removing metastases limited to the lungs, they can greatly improve survival, in what would otherwise be a dismal prognosis. This is not a small procedure, so patients have to be healthy enough to endure a surgical resection of the lung tumor(s).
After initial treatment, patients should be seen and examined every 3-4 months for 3 years, every 6 months for 2 years, then annually (may be less frequent for stage I cases). Periodic CT scans or MRIs of the original tumor site may allow detection of a recurrence before symptoms arise. Abdominal sarcomas should be scanned every 3-6 months for 3 years, then annually, as recurrence is more difficult to detect in the abdomen using physical examination alone. Chest x-ray or CT scan of the chest can be performed every 6-12 months to monitor for lung metastases.
Hyperthermic Isolated Limb Perfusion (HILP) is a technique that is being used to treat STS in the extremities (legs or arms). The circulation to that limb is basically cut off and chemotherapy is infused directly into it, all while the limb's temperature is heated above normal temperatures. This technique makes the chemotherapy far more potent than administering it through a regular IV. HILP is being studied in patients who would otherwise require amputation or those who have a localized area of recurrence.
Chemotherapy is being studied in high doses, but results have yet to improve survival much. There are new, investigational agents being studied in clinical trials, but given the small numbers of cases and the number of subtypes of STS, it can take considerable time for these to be proven worthy.
Clinical trials have played and continue to play an important role in the treatment of sarcomas. In the past 20 years, considerable improvements have been made in sarcoma therapy, particularly surgical treatments, with great improvements in rates of amputations. The treatments we have today were refined through clinical trials, and many new avenues continue to be explored. Talk with your physician about current clinical trials for sarcomas in your area or visit our clinical trials matching service.
This article is meant to give you a better understanding of soft tissue sarcomas. Use this knowledge when meeting with your physician, making treatment decisions, and continuing your search for information. You can learn more about sarcoma on OncoLink through the related links on the right.
Links to other resources
Sarcoma Foundation of America – The SFA raises money for sarcoma research and aims to raise awareness of sarcoma. The site has information for patients as well.
Sarcoma Alliance– This website, started by a sarcoma survivor, is based on the mantra "guidance, education, and support". They also maintain a list of specialty centers.
Liddy Shriver Sarcoma Initiative – Increases public awareness of sarcoma, raises funds for research, and provides support and information to sarcoma patients, their families, and medical professionals.
NCI STS Information – Overview of STS on the National Cancer Institute Site.
Types of Soft Tissue Sarcoma (and the tissue it arises from)