Introduction and frequency
Sarcomas are malignant tumors that, unlike cancers originating from epithelial cells, arise from cells of mesenchymal origin, i.e. connective tissue in the broadest sense. These include bone, cartilage, adipose tissue, blood vessels, and hematopoietic tissues, and sarcomas can arise in any of these. The basic division of sarcomas is into bone sarcomas and soft tissue sarcomas. The term sarcoma comes from the Greek word for flesh. Sarcomas are relatively rare tumors, and some forms can appear already in childhood. According to the place of origin, the most common sarcomas are the extremities (50%), followed by the trunk (40%) and the head (10%).
Risk factors
Risk factors for the development of sarcoma are still insufficiently known. Exposure to radiation increases the risk, as do some chemicals (thorium dioxide, arsenic...). In Kaposi's sarcoma, the influence of herpes virus 8 and HIV is important. It is known that soft tissue sarcomas occur more often in people with some of the inherited genetic syndromes, such as Gardner syndrome, Li-Fraumeni syndrome, tuberous sclerosis and some others.
Signs and symptoms
Symptoms of soft tissue sarcoma vary depending on the type and site of origin. Firm, painless lumps / nodules often appear, which grow over time.
Establishing a diagnosis
The diagnosis is not simple because it is a very heterogeneous disease. According to the classification of the World Health Organization from 2013, there are over 100 different subtypes of this disease. It is necessary to do a biopsy and then consult a pathologist who has experience in diagnosing sarcoma. Careful planning of the initial biopsy is important in order not to compromise the possibility of subsequent surgical treatment if it is indicated. Other tests (CT / MR and others) are performed according to the indication. In many cases, CT of the chest is required, because the lungs are the most common site of metastasis. Lymph nodes are rarely affected, in about 3% of cases. Adequate tumor markers do not exist. You can read more about the diagnosis of malignant diseases in general in a separate article .
Figure 1. Gastrointestinal stromal tumors (GIST) are a specific type of sarcoma that arises in the digestive system. Namely, the intestinal wall, in addition to the epithelial cells from which a typical adenocarcinoma in the intestine or stomach can arise, also contains connective tissue from which a sarcoma can develop. Fortunately, these tumors are relatively rare and have a better prognosis compared to classical cancers in the intestine and stomach.
Stage of the disease
Soft tissue sarcomas are divided, like other malignant diseases, into 4 stages. Factors associated with a worse prognosis are age over 60 years, tumors larger than 5 cm in diameter, high grade and positive margins after surgery.
In stage I, the tumor is grade 1.
In stage II, the tumor is grade 2 or 3, but its maximum diameter is up to 5 cm.
In stage III, the tumor is grade 2 or 3 and has a maximum diameter greater than 5 cm
In stage IV, the disease has spread to distant parts of the body (metastases).
Treatment
Stage I. Low-grade sarcomas have a low metastatic potential, but the disease can return locally after treatment. Given the above, the choice of treatment is surgery with 1 to 2 cm of healthy tissue margins in all directions. In case of unresectable tumors or when surgery is not possible for any reason (high risk of surgery due to other diseases, need to amputate a limb to achieve clean margins...), radiotherapy can be applied.
Stage II . The basis is surgical treatment, but the risk of metastases is higher. In case of sarcoma on the extremities, local control of the disease can be achieved not only by amputation of the limb, but also by sparing surgery (limb-sparing) with the addition of radiotherapy before or after the procedure. In the case of tumors in the area of the back part of the abdomen (retroperitoneum), it is often difficult to achieve a complete resection of the tumor due to its size and anatomical location, and in many cases it is necessary to remove some of the organs in the abdomen and apply additional radiotherapy. In the case of an estimated high risk for metastasis, chemotherapy is added to the treatment.
Stage III . The basis of treatment is surgery, to which in most patients radiotherapy and/or chemotherapy are added.
Stage IV . In case of extended disease, it is necessary to apply systemic treatment - chemotherapy or targeted therapy. The choice of cytostatic depends on the type of sarcoma. Some of the most commonly used are doxorubicin, gemcitabine, trabectedin, eribulin, pazopanib, ifosfamide (alone or in combination with etoposide), dacarbazine, temozolomide, vinorelbine and regorafenib. In case of stabilization of the primary tumor, surgical treatment of lung metastases can be considered. It is important to note that one of the options is to be included in appropriate clinical studies.
Our team favors personalized treatment of sarcoma in the metastatic stage of the disease, given the generally unsatisfactory results of chemotherapy treatment. Sarcomas are tumors that can have specific genetic changes (mutations) that can enable the application of highly effective targeted therapy. In accordance with the above, we recommend, in consultation with our oncologist, to carry out a complete genetic profiling of the tumor, in order to analyze whether the disease is reactive to any of the targeted drugs or immunotherapy, in which case the treatment results can be extraordinary.
Additional points of interest
Gastrointestinal stromal tumor (GIST) is a specific type of soft tissue sarcoma and is the most common sarcoma of the gastrointestinal tract. GIST occurs in the digestive system anywhere from the esophagus to the rectum, and is most often found in the stomach and small intestine. Rarely, GISTs arise elsewhere in the abdomen outside the digestive tract. In most patients, the disease is less aggressive than a typical sarcoma, and the basis of treatment in localized disease is surgery, while systemic therapy is used in the presence of metastases. In the framework of systemic therapy, a whole series of drugs is approved, of which the targeted drug imatinib is mostly used in the 1st line of therapy, but depending on the tolerance of the therapy and the results of the treatment, others may also be used. For example, avapritinib is recommended for patients with a detected PDGFRA exon 18 mutation.
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