How are soft tissue sarcomas in children treated?

The strategy of treating tumors in children and adults is different, which is connected with several points:

• carrying out organ-saving operations in children is associated with great technical difficulties due to anatomical and functional features;
• the use of radiotherapy in young children can lead to serious complications (for example, disruption in the growth of individual organs and the body as a whole), more pronounced than in adults;
• In children's oncology, more stringent schemes of high-dosage chemotherapy have been developed. Including multicomponent regimens (carrying out similar chemotherapeutic treatment in adults is often impossible in connection with the worst tolerability);
• the long-term effects of all therapies in children are socially more significant due to the potentially longer life expectancy compared with adults.

The listed differences determine the need to carefully choose treatment tactics with the obligatory consideration of the individual characteristics of the child and the potential risk of delayed complications.

In connection with the rarity of non-bloomingomyosarcoma soft tissue tumors, their treatment should be carried out within the framework of multicenter studies that allow obtaining reliable results and on their basis optimize the methods of treatment. In the treatment of this type of tumors should take part specialists of various profiles: surgeons, chemotherapists, radiologists. In connection with the need to conduct crippling operations in a number of cases, it is advisable to include early in the treatment process orthopedists, rehabilitation specialists and psychologists, from which the quality of life of the patient will in no small measure depend on.

At the surgical stage of treatment, the possibility of complete excision of the tumor within the limits of healthy tissues is determined. This is an extremely important prognostic factor. The absence of a residual tumor means a favorable prognosis. If the residual tumor is preserved, the necessity and possibility of a repeat radical operation is considered.

The role of chemotherapy in soft tissue sarcomas is ambiguous. With respect to chemotherapy, the division of tumors into sensitive (PMC-like), moderately sensitive and insensitive is generally accepted. On the basis of this division, a number of modern programs for the treatment of soft tissue sarcomas (CWS, SIOP) have been constructed. Chemotherapy-sensitive tumors include rhabdomyosarcoma, extrinsic Ewing sarcoma, peripheral neuroectodermal tumors, synovial sarcoma. Moderately sensitive include malignant fibrocytic histiocytes, leiomyosarcoma, malignant vascular tumors, alveolar soft tissue sarcoma and liposarcoma. Insensitive to chemotherapy fibrosarcoma (with the exception of congenital) and neurofibrosarcoma (malignant schwannoma).

With the exception of rhabdomyosarcoma and synovial sarcoma, in large prospective studies using adjuvant chemotherapy in children with soft tissue sarcomas, there was no improvement in treatment outcomes (total and event-free survival).

The basic drugs used in the treatment of soft tissue sarcomas. Vincristine, dactinomycin, cyclophosphamide and doxorubicin (VACA regimen) have long remained. A number of studies have shown a greater efficacy of ifosfamide compared with cyclophosphamide. In connection with the unsatisfactory results of treatment with incomplete removal of the tumor, new drugs, more effective combinations and chemotherapy regimens are being searched.

The role of radiation therapy in the treatment of soft tissue sarcomas is to provide local control of the tumor. The radiation doses in various protocols range from 32 to 60 Gy. According to some researchers, the joint use of surgical and radiation treatment allows to achieve adequate local control in 80% of patients. In some clinics, alternative methods of radiation exposure are actively introduced - brachytherapy and intraoperative irradiation with an electron beam. Preoperative irradiation of the tumor, which showed good results in adults, is less commonly used in pediatric oncology.

With local recurrence of the disease, they try to cut the tumor again. In these cases, non-adjuvant chemotherapy is effective, including in children of younger age group with fibrosarcoma and hemangiopereticoma. Among all soft tissue sarcomas, these tumors, as well as dermatofibrosarcoma and malignant fibrocytic histiocytoma, are less aggressive and rarely metastasize. Their cure is often possible by surgical removal.

With not completely removed alveolar soft tissue sarcoma, chemotherapy is ineffective.

Desmoplastic tumor from small round cells - a tumor of unknown histogenesis - is usually localized in the abdominal cavity and small pelvis, which makes it difficult to completely remove it. In this case, the tactic is based on the complex use of surgical, radiation and chemotherapeutic treatment.

Treatment for light-cellular sarcoma of soft tissues is mainly surgical with possible irradiation with residual tumor. Attempts to use chemotherapy in this case proved ineffective.

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

Gemangioendothelioma, malignant, occupying an intermediate position between hemangioma and hemangiosarcoma, in children is most often localized in the liver. It can grow asymptomatically and even spontaneously regress. Sometimes this tumor accompanies the development of consumption coagulopathy (Kazabaha-Merrita syndrome). In this case, an active surgical tactic is necessary. There are reports of successful use of chemotherapy (vincristine, dactinomycin, cyclophosphamide) and interferon alfa-2a. If there is no effect, liver transplantation is indicated.

Special attention should be paid to the therapeutic tactics of extraosseous osteosarcoma. The effectiveness of chemotherapy with 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 therapy of soft tissue sarcomas.

If it is not possible to completely excise the tumor or in the presence of metastases, radiotherapy and chemotherapy are mandatory. The overall four-year survival with the VACA regimen is approximately 30%, the recurrence-free survival rate is 11%. Surgical treatment of solitary metastases is indicated for their localization in the lungs. Currently, there are persistent attempts to increase the effectiveness of treatment in this group of patients through the intensification of chemotherapy and the use of new regimens with the inclusion of ifosfamide and doxorubicin.

An unresolved problem is the therapy of recurrences of soft tissue sarcomas. When constructing treatment tactics, the previous therapy, the 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 efficacy of radiotherapy and chemotherapy in relapses is not clear 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 age of the patient, and also on a number of factors specific to a particular tumor. In fibrosarcoma and hemangiopericytoma, the prognosis is significantly better in younger patients. With neurofibrosarcoma and liposarcoma, the prognosis determines the completeness of excision. With 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 (hemangiendothelioma, angiosarcoma, lymphosarcoma). The presence of metastases is an extremely unfavorable prognostic factor for any neoplasm. Late metastases, significantly worsening the prognosis, are characteristic of alveolar sarcoma and melanoma of soft tissues.

[1], [2], [3], [4], [5], [6]