How are soft tissue sarcomas in children treated?

The treatment strategy for tumors in children and adults is different, which is due to several factors:

• performing organ-preserving operations in children is associated with great technical difficulties due to anatomical and functional features;
• the use of radiation therapy in young children can lead to serious complications (for example, disruption of the growth of individual organs and the body as a whole), more pronounced than in adults;
• In pediatric oncology, more stringent high-dose chemotherapy regimens have been developed, including multicomponent regimens (carrying out such chemotherapy treatment in adults is often impossible due to poorer tolerability);
• The long-term effects of all types of therapy in children are socially more significant due to their potentially longer life expectancy compared to adults.

The listed differences determine the need to carefully select treatment tactics, taking into account the individual characteristics of the child and the potential risk of delayed complications.

Due to the rarity of non-rhabdomyosarcoma soft tissue tumors, their treatment should be carried out within the framework of multicenter studies that allow obtaining reliable results and, based on them, optimizing treatment methods. In the treatment of this type of tumor, specialists of various profiles should participate: surgeons, chemotherapists, radiologists. Due to the need to perform mutilating operations in some cases, it is advisable to early include orthopedists, rehabilitation specialists and psychologists in the treatment process, on whom the patient's quality of life will largely depend in the future.

At the surgical stage of treatment, the possibility of complete excision of the tumor within healthy tissues is determined. This is an extremely important prognostic factor. The absence of residual tumor means a favorable prognosis. If residual tumor remains, the need and possibility of repeated radical surgery are considered.

The role of chemotherapy in soft tissue sarcomas is ambiguous. In relation to chemotherapy, it is generally accepted to divide tumors into sensitive (PMC-like), moderately sensitive and insensitive. A number of modern programs for the treatment of soft tissue sarcomas (CWS, SIOP) are based on this division. Tumors sensitive to chemotherapy include rhabdomyosarcoma, extraosseous Ewing's sarcoma, peripheral neuroectodermal tumors, synovial sarcoma. Moderately sensitive tumors include malignant fibrocytic histiocytoma, leiomyosarcoma, malignant vascular tumors, alveolar sarcoma of soft tissues and liposarcoma. Fibrosarcoma (except for congenital) and neurofibrosarcoma (malignant schwannoma) are insensitive to chemotherapy.

With the exception of rhabdomyosarcoma and synovial sarcoma, large prospective studies have not shown improvement in outcome (overall and event-free survival) using adjuvant chemotherapy in children with soft tissue sarcomas.

The basic drugs used in the treatment of soft tissue sarcomas have long been vincristine, dactinomycin, cyclophosphamide and doxorubicin (VACA regimen). A number of studies have shown the greater effectiveness of ifosfamide compared to cyclophosphamide. Due to the unsatisfactory results of treatment to date with incomplete removal of the tumor, a search is underway for new drugs, more effective combinations and chemotherapy regimens.

The role of radiation therapy in the treatment of soft tissue sarcomas is to ensure local tumor control. Radiation doses in various protocols vary from 32 to 60 Gy. According to some researchers, the combined use of surgical and radiation treatment allows for adequate local control in 80% of patients. Some clinics are actively introducing alternative methods of radiation exposure - brachytherapy and intraoperative electron beam irradiation. Preoperative tumor irradiation, which has shown good results in adults, is used less frequently in pediatric oncology.

In case of local recurrence of the disease, an attempt is made to resect the tumor. In these cases, neoadjuvant chemotherapy is effective, including in younger children with fibrosarcoma and hemangiopericytoma. Among all soft tissue sarcomas, these tumors, as well as dermatofibrosarcoma and malignant fibrocytic histiocytoma, are less aggressive and rarely metastasize. They can often be cured by surgical removal.

In cases where alveolar sarcoma of soft tissues has not been completely removed, chemotherapy is ineffective.

Desmoplastic small round cell tumor - a tumor of unknown histogenesis - is usually localized in the abdominal cavity and small pelvis, which makes its complete removal difficult. In this case, the tactics are based on the complex use of surgical, radiation and chemotherapeutic treatment.

Treatment for clear cell soft tissue sarcoma is primarily surgical with possible irradiation for residual tumor. Attempts to use chemotherapy in this case have proven ineffective.

In highly malignant tumors such as angiosarcoma and lymphangiosarcoma, the prognosis is determined by the possibility of their complete removal. There is a report of the successful use of paclitaxel in this type of tumor.

Hemangioendothelioma, which occupies an intermediate position between hemangioma and hemangiosarcoma in malignancy, is most often localized in the liver in children. It can grow asymptomatically and even regress spontaneously. Sometimes this tumor is accompanied by the development of consumption coagulopathy (Kasabach-Merritt syndrome). In this case, active surgical tactics are necessary. There are reports of successful use of chemotherapy (vincristine, dactinomycin, cyclophosphamide) and interferon alpha-2a. If there is no effect, liver transplantation is indicated.

Treatment tactics for extraosseous osteosarcoma deserve special attention. The effectiveness of chemotherapy for this type of tumor remains poorly understood. However, according to some authors, treatment of this neoplasm should be carried out according to the principles developed for the treatment of soft tissue sarcomas.

If complete excision of the tumor is impossible or if metastases are present, radiation and chemotherapy are mandatory. The overall four-year survival rate when using the VACA scheme is approximately 30%, and relapse-free survival is 11%. Surgical treatment of solitary metastases is indicated when they are localized in the lungs. Currently, persistent attempts are being made to improve the effectiveness of treatment in this group of patients by intensifying chemotherapy and using new schemes including ifosfamide and doxorubicin.

An unsolved problem is the treatment of recurrent soft tissue sarcomas. When developing treatment tactics, previous therapy, localization of the process and the patient's condition are taken into account. Cure is possible in a small number of cases with complete excision of the tumor and its metastases. The effectiveness of radiation and chemotherapy in relapses has not been clarified and requires evaluation in randomized multicenter studies.

Forecast

The prognosis for soft tissue sarcomas depends on the histological type, the completeness of surgical resection, the presence or absence of metastases, the patient's age, and a number of factors specific to a particular tumor. For fibrosarcoma and hemangiopericytoma, the prognosis is significantly better in younger patients. For neurofibrosarcoma and liposarcoma, the prognosis is determined by the completeness of excision. For leiomyosarcoma, the prognosis is worse if the tumor develops within the gastrointestinal tract. The prevalence of the process, the volume of the residual tumor, and the degree of malignancy are decisive prognostic factors for vascular tumors (hemangioendothelioma, angiosarcoma, lymphosarcoma). The presence of metastases is an extremely unfavorable prognostic factor for any neoplasm. Late metastases, which significantly worsen the prognosis, are characteristic of alveolar sarcoma and melanoma of soft tissues.

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