What is Sarcoma?
A sarcoma is a cancer that arises from transformed cells of mesenchymal (connective tissue) origin. Connective tissue is a broad term that includes bone, cartilage, fat, vascular, or hematopoietic tissues, and sarcomas can arise in any of these types of tissues. As a result, there are many subtypes of sarcoma, which are classified based on the specific tissue and type of cell from which the tumor originates. It is important to note that sarcomas are primary connective tissue tumors, meaning that they arise in connective tissues.
Symptoms of bone sarcomas typically include bone pain, especially at night, and swelling around the site of the tumor. Symptoms of soft tissue sarcomas vary, but often present as firm, painless lumps or nodules. Gastrointestinal stromal tumors (a subtype of soft tissue sarcoma) often are asymptomatic, but can be associated with vague complaints of abdominal pain, a feeling of fullness, or other signs of intestinal obstruction.
Diagnosis of bone sarcomas begins with a thorough history and physical examination which may reveal characteristic signs and symptoms (see Signs and Symptoms above). Laboratory studies are not particularly useful in diagnosis, although some bone sarcomas (such as osteosarcoma) may be associated with elevated alkaline phosphatase levels, while others (such as Ewing Sarcoma) can be associated with elevated erythrocyte sedimentation rate. Importantly, however, none of these laboratory findings are specific to bone sarcomas, meaning that elevations in these lab values are associated with many other conditions as well as sarcoma, and thus cannot be relied upon to conclusively diagnose sarcoma.
Diagnosis of soft tissue sarcomas also begins with a thorough history and physical examination. Imaging studies can include either CT or MRI, although CT tends to be preferred for soft tissue sarcomas located in the thorax, abdomen, or retroperitoneum. Positron emission tomography (PET) also may be useful in diagnosis, although its most common use is for staging (see below). As with bone sarcomas, definitive diagnosis requires biopsy of the tumor with evaluation of histology by a trained pathologist.
Surgery is the most common form of the treatment for most sarcomas that have not spread to other parts of the body. Limb-sparing surgery, as opposed to amputation, can now be used to save the limbs of patients in at least 90% of extremity (arm or leg) sarcoma cases. Additional treatments, including chemotherapy and radiation therapy (also called "radiotherapy"), may be administered before surgery (called "neoadjuvant" chemotherapy or radiotherapy) and/or after surgery (called "adjuvant" chemotherapy or radiotherapy). The use of neoadjuvant or adjuvant chemotherapy and radiotherapy significantly improves the prognosis for many sarcoma patients.
Treatment of sarcoma, especially when the sarcoma has spread, or "metastasized", often requires chemotherapy but existing chemotherapeutic medicines are associated with significant toxicities and are not highly effective in killing cancer cells. Therefore, research to identify new medications to treat sarcoma is bing conducted as of 2019. One possibility is the use of cancer immunotherapy (e.g., immune checkpoint inhibitors like anti-PD1, anti-PDL1, and anti-CTLA4 agents) to treat sarcomas.
Journal of Clinical Oncology and Cancer Research,