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Soft Tissue Sarcoma: Staging, Grading, Risk Stratification, Treatment

Soft tissue sarcoma staging systems are used to describe the severity of cancer, based on the size, extent of invasion, and the spread of disease to different body parts. Staging helps to determine disease prognosis and treatment strategy.

STS of the Trunk, Extremities (limbs), and Retroperitoneum:

TNM is the most commonly used system for staging STSs of the trunk, extremities (limbs), and retroperitoneum by the medical community.

“T” stands for “Tumor Size”, “N” for “Lymph Nodes”, and “M” for “Metastasis”. Numbers and/or letters after T (1, 2, 3, and 4), N (0 and 1), and M (0 and 1) provide more details about each of these factors.

Additionally, STS of the trunk, extremities (limbs), and retroperitoneum is graded to assess the aggressiveness of the disease. A three-tiered French Federation of Cancer Centers Sarcoma Group (FNCLCC) grade system is the most commonly used system to grade the STS.

In this system, the grade of a tumor is determined with the help of 3 parameters: differentiation (appearance of cell morphology under the microscope), mitotic activity (rate of cancerous cell division), and extent of necrosis (extent of dead tissue present in the tumor mass).

Each parameter is scored as follows: differentiation (1–3), mitotic activity (1–3), and necrosis (0–2), where a higher score indicates abnormal cells morphology, high rate of cell division, and presence of high amount of dead tissue, respectively. The scores are added to assign the grade to a tumor, where G1 = a score of 2 or 3; G2 = a score of 4 or 5; and G3 = a score of 6 to 8.

Once T, N, and M categories and the overall grade of a tumor are determined through different diagnostic techniques, this information is combined to assign an overall stage (from 0 to IV) to the disease. Following table describes the characteristics of different stages assigned to the STS of the trunk, extremities (limbs), and retroperitoneum:

STAGE TNM and GRADE Trunk & Extremities Retroperitoneum
IA T1 N0 M0 G1/X The primary tumor is </=5 cm in size. No spread to nearby lymph nodes or distant body parts. The assigned grade is G1 or grade could not be assigned or is unknown. The primary tumor is </=5 cm in size. No spread to nearby lymph nodes or distant body parts. The assigned grade is G1 or grade could not be assigned or is unknown.
IB T2-4 N0 M0 G1/X The primary tumor size may range from >5 cm to >15 cm. No spread to nearby lymph nodes or distant body parts. The assigned grade is G1 or grade could not be assigned or is unknown. The primary tumor size may range from >5 cm to >15 cm. No spread to nearby lymph nodes or distant body parts. The assigned grade is G1 or grade could not be assigned or is unknown.
II T1 N0 M0 G2-3 The primary tumor is </=5 cm in size. No spread to nearby lymph nodes or distant body parts. The assigned grade is G2 or G3. The primary tumor is </=5 cm in size. No spread to nearby lymph nodes or distant body parts. The assigned grade is G2 or G3.
IIIA T2 N0 M0 G2-3 The primary tumor is >5 cm but </=10 cm in size. No spread to nearby lymph nodes or distant body parts. The assigned grade is G2 or G3. The primary tumor is >5 cm but </=10 cm in size. No spread to nearby lymph nodes or distant body parts. The assigned grade is G2 or G3.
IIIB T3-4 N0 M0 G2-3 The primary tumor size may range from >10 cm to >15 cm. No spread to nearby lymph nodes or distant body parts. The assigned grade is G2 or G3. The primary tumor size may range from >10 cm to >15 cm. No spread to nearby lymph nodes or distant body parts. The assigned grade is G2 or G3.
Any T N1 M0 Any G N/A The primary tumor of any size. The disease has spread to nearby lymph nodes. No spread to distant body parts. The assigned grade may have any value.
IV Any T N1 M0 Any G The primary tumor of any size. The disease has spread to nearby lymph nodes. No spread to distant body parts. The assigned grade may have any value. N/A
Any T Any N M1 Any G The primary tumor of any size that might or might not have spread to nearby lymph nodes. The disease has spread to distant body parts, such as the lungs. The assigned grade may have any value. The primary tumor of any size that might or might not have spread to nearby lymph nodes. The disease has spread to distant body parts, such as the liver or lungs. The assigned grade may have any value.

Stage grouping for STS in the abdomen, thoracic visceral organs, and Head & neck region require further data collection and has not been established yet.

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TREATMENT

The soft tissue sarcoma treatment usually depends on many factors, including but not limited to the type of sarcoma, stage of disease, the location of the disease, performance status, patient’s preference, along with other factors. Following are the preferred treatment approaches for different stages of soft tissue sarcoma, but the final decision is taken after clinical assessment of the patient by an oncologist.

STAGE TREATMENT
Stage I Stage I-STSs are low-grade tumors of any size. If possible, surgical resection with negative margins is considered as the standard treatment.

In a case when negative margins were not obtained, further surgical resection to remove all cancerous tissue is the preferred approach. If further surgery is not possible, radiotherapy may be employed to decrease the chances of disease recurrence.

If the tumor is present at such a location (e.g. retroperitoneum, trunk, and head and neck,) that it cannot be entirely removed without functional disability, radiotherapy may be employed as the first-line treatment. This may cause the tumor to shrink sufficiently that it can be removed surgically.
Stage II or III Most Stage II- and III-STSs are high-grade tumors that tend to spread quickly and some of them have already spread to nearby lymph nodes. If possible (without any significant functional disability), surgical resection with negative margins is considered as the standard treatment. Any lymph node with the sign of disease spread should also be removed. Radiotherapy with/without chemotherapy may be considered after complete removal of the tumor.
In case of the positive margin, further surgical resection to remove all cancerous tissue is the preferred approach. If further surgery is not possible, radiotherapy may be employed to decrease the chances of disease recurrence.

If tumor is too large or present at such a location (e.g. retroperitoneum, trunk, and head and neck,) that it cannot be entirely removed without functional disability, or if surgery is not possible due to overall health of the patient, radiotherapy with or without chemotherapy may be employed as the first-line treatment. This may cause the tumor to shrink sufficiently that it can be removed with surgery. Further treatment, such as more radiotherapy/chemotherapy and/or supportive care or any other treatment may be provided based on the response to initial treatment.
Stage IV Stage IV-STSs are cancers that have spread to a distant body parts. For patients with a single site of disease spread and a small primary tumor that can be entirely removed with surgery, a surgical resection with the negative surgical margins for the primary tumor and the distant site is considered as the preferred treatment. As appropriate, tumor ablation, embolization, or radiotherapy may be employed instead of surgical resection for the secondary tumors.
For patients with a widespread disease or when the primary and secondary tumors cannot be removed by surgery, chemotherapy is usually employed. Any other suitable treatment may be employed as palliative treatment.

Following is the brief description of various treatment types employed for different STSs:

  1. Surgery: Surgery is the treatment of choice for most early-stage and some higher stage STSs that has not spread to distant body parts and can be completely removed.

    The goal of surgery is to remove entire cancerous tissue along with some healthy tissue. This is possible for some early-stage disease where the tumor is confined to a specific area, and complete resection can be performed with ease.

    However, a complete resection is not always possible, such as in the case of advanced-stage disease, the disease involving a vital organ/structure, or when a surgical resection will lead to a significant functional disability. Surgery may also be performed to collect biopsy sample in some cases.

  2. Radiation Therapy: Radiation therapy uses high-energy x-rays or other high-energy radiations which are directed to the affected area to kill cancerous cells. Radiotherapy can be employed either by using an external radiation source (external beam radiation therapy) or by directly placing the source of radiation near the cancer tissue (brachytherapy).

    It can be employed alone as the first-line treatment for certain early-stage STSs or can be combined with other treatment options, such as surgery and/or chemotherapy for some advanced-stage STSs. It may be considered in some patients who cannot tolerate surgery or in case of disease recurrence after primary treatment. It is sometimes used for palliation of symptoms of the disease such as pain, bleeding, and obstructive problems.

  3. Chemotherapy: Chemotherapy means treatment with anti-cancer drugs that kill or decrease the growth of rapidly growing cancer cells. Chemotherapy is generally employed for the treatment of advanced stage STS that has spread to distant body parts and cannot be removed completely with surgical resection.

    Depending on the physician’s preference and patient’s condition, it may also be combined with other treatment options, like radiotherapy, to accelerate the benefit achievement. It may be associated with side effects due to its effect on normal body cells apart from cancerous cells.

  4. Targeted Therapy: Targeted drugs works differently than chemotherapy drugs that they target a specific gene or protein characteristic of the cancer cells that help them to divide and grow indefinitely.

    For example, Olaratumab targets PDGFR-alpha, Pazopanib targets tyrosine kinases, Imatinib targets both the KIT and PDGFRA proteins, etc. They are generally used alone or in combination with chemotherapy for the treatment of advanced-stage STSs or STSs that possess specific proteins.

  5. Palliative Treatment: It do not directly treat STSs but helps in improving the overall quality of life by providing relief from the symptoms and by reducing the suffering caused by the disease. It is generally given as supportive care for advanced staged STSs along with other treatments.

    It may include but not limited to: using drugs or other interventions to reduce swelling, pain, bleeding, and other symptoms such as nausea, vomiting, and diarrhea; surgical interventions or radiotherapy may also be employed.

It is very important to assess the benefits of each treatment option versus the possible risks and side effects before making a treatment decision. Sometimes, patient’s choice and health condition are also important to make a treatment choice.

Following are the goals for soft tissue sarcoma treatment:

  • Prolongation of life.
  • Reduction of symptoms.
  • Improvement of overall quality of life.
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