Ewing’s Sarcoma

(PNET)

Ewing’s sarcoma is a round cell tumor, a component of Primitive neuroectodermal family of tumors (PNET). It is the second most common primary bone tumor affecting age group of 5-20 years commonly.

What is the cause of Ewing’s sarcoma?

The etiology of Ewing’s sarcoma is evident as reciprocal translocation between chromosome 11 and 22 in 85 % of cases. Immunohistochemistry (IHC) identifies CD99, Fli-1, vimentin, s-100, leu-7.

How in Ewing’s Sarcoma identified?

Pain is the most common presenting symptom, increasing in the night and may be associated with trivial trauma. A palpable mass grows rapidly thereafter accompanied by raise in temperature and the symptoms are noticed for duration of 3-9 months associated with loss of weight and appetite.

It is common to suspect local inflammation or osteomyelitis based on the presentation and duration of symptoms.

It most commonly involves bones such as pelvis followed by shaft or diaphysis of long bones, scapula, clavicle, chest wall and soft tissues.

Nearly 75 % of individuals present with solitary primary tumor without any distant metastases.

How to know the extent & spread of Ewing’s sarcoma in the body?

The individual undergoes successive examinations such as plain radiograph, MRI followed by Biopsy.

Increase in ESR and LDH is noted in majority of individuals with Ewing’s sarcoma.

A Bone marrow aspiration is performed from posterior aspect of iliac bone to look for marrow involvement.

PET CT (whole body) is performed to identify metastases and complete staging.

10 % of patients present with microscopically detectable bone metastases.

How is of Ewing’s sarcoma treated?

The treatment of Ewing’s sarcoma is by a multidisciplinary team similar to osteosarcoma.

Ewing’s sarcoma has a better response to chemotherapy (Vincristine, Doxorubicin and Cisplatin-VAC protocol is commonly followed) and radiotherapy compared to osteosarcoma, but better outcomes are obtained when neoadjuvant chemotherapy is followed by surgical removal of primary tumor infrequently followed by adjuvant therapy.

Radiotherapy is used as adjuvant therapy when the surgical margins after tumor removal are narrow or post chemotherapy when the tumor is found in inaccessible sites such as inside pelvis, sacrum and large size of primary tumor (It is debated that risk of recurrence with radiotherapy alone is 10-20 %).

How is Limb Salvage possible in Ewings’s Sarcoma?

Surgical removal is with wide margins followed by reconstruction of the defect.

Reconstruction options include the same modalities as discussed in osteosarcoma which are individualized.

The advantage in Ewing’s sarcoma is that in certain situations radiotherapy can be provided to the tumor preoperatively when the initial tumor size appears large and the surgical margin expected is narrow increasing the risk of recurrence.

If an individual has distant metastases (lung most common), it can be surgically removed after removal of primary tumor.

Postoperatively adjuvant chemotherapy is provided (4-6 months) and can be altered based on tumor necrosis response after neoadjuvant chemotherapy.

Rehabilitation is provided according to the type of reconstruction.

How often should I visit the doctor?

The individual is followed up every 3 months for the first 2 years, followed by 6 months every 3 years (aggressive monitoring of the patient until 5 years).

Overall survival of primary non metastatic Ewing’s sarcoma at presentation is 60 – 70 %.

Distant metastases and local recurrence may necessitate change in chemotherapy protocol depending on the nature of event.

Solitary metastasis and local recurrences require to be surgically removed. Survival of this specific category of individuals is 20-30 % at 5 years.

Occurrence of multiple widespread metastases or multiple local recurrences increase morbidity and mortality risk.

Are there any prognostic factors for Ewing’s sarcoma?

Certain prognostic features have been identified for Ewing’s sarcoma.

Better prognosis is for primary tumor without metastasis, long bone involvement compared to pelvis and axial sites, small tumor size (less than 200 ml), and children compared to adults, lung metastases compared to bone metastasis and response to initial chemotherapy.