Current and advancing systemic treatment options for soft tissue sarcomas

INTRODUCTION

Soft tissue sarcomas are a collection of rare malignancies, the treatment of which has evolved over time. Although cytotoxic chemotherapy remains the cornerstone of management of metastatic disease, many new treatments have been developed or show great promise in the treatment of soft tissue sarcoma. Research into the different underlying pathogenesis of individual subtypes has driven progress in treatment. This has allowed development of treatments targeted to specific subtypes of sarcoma.

AREAS COVERED

We provide a review of the current field of systemic therapy in soft tissue sarcoma. This is followed by an in-depth analysis of recent developments in treatment, as well as new treatments that are aimed at specific subtypes of sarcoma, and the biological rationale behind these therapies. We also look in detail at the promising new agents currently in development.

EXPERT OPINION

Much progression has been made in treatment of soft tissue sarcomas with multiple exciting new treatments in development. However outcomes in general remain poor. Further research into the underlying pathogenesis of soft tissue sarcomas may help deliver more effective systemic therapies. Increased collaboration between basic science, translational and clinical investigators is required at national and international levels to maximise progress.

Treating soft tissue sarcomas with adjuvant chemotherapy

Surgery remains the cornerstone of treatment and the only curative loco-regional approach of localized resectable soft tissue sarcoma (STS) in 2011: the usual first-line treatment is wide margin surgery plus radiotherapy, especially in the case of primary tumors arising in the limbs. An optimal initial R0 resection is one of the most reproducible and reliable prognostic factors for survival in resectable STS. Nevertheless, despite improved local control rates, more than half of the patients still develop and die from unresectable, locally advanced, and/or metastatic disease. Unfortunately, very few cytotoxic drugs have shown activity in this clinical setting with the exception of doxorubicin, ifosfamide, and to a lesser extent, dacarbazine. A conventional-dose, single-agent chemotherapy is still considered to be the standard treatment for metastatic disease. The impact of adjuvant chemotherapy after resection of a high-grade STS remains controversial due to the lack of reproducible impact on survival. Because STS is a rare disease, most trials have involved a relatively small number of patients, with heterogeneous groups of histological/molecular subtypes of sarcomas, initial sites of the disease, and patient's characteristics. In a few trials, a lower risk for local recurrence was observed among patients receiving adjuvant chemotherapy but without any significant gain in overall survival. A meta-analysis based on individual data of these randomized studies has confirmed a significant impact of adjuvant chemotherapy on relapse, either local or metastatic, but without any significant benefit on survival. It should be of importance to include the last recent large trials in a new meta-analysis of source data in order to more carefully analyze a possible benefit of systemic adjuvant chemotherapy in localized sarcoma. Until this study is performed, it is an obvious conclusion that adjuvant chemotherapy has not reproducibly demonstrated its capacity to improve overall survival and relapse-free survival in an unselected population of patients. In 2011, there is therefore an urgent need to determine whether or not there are small subpopulations of patients truly benefiting from adjuvant chemotherapy (with conventional agents), and to identify prospectively these populations. With the exception of male, older than 40 years, with a non-optimal resection of their primary (R1 resection) or in the subgroup of grade 3 STS, no other relevant clinical prognostic/predictive factors have been highlighted. The take home messages in 2011 could be as follows: (1) adjuvant chemotherapy is not recommended routinely in high-grade STS; (2) adjuvant chemotherapy is recommended in patients underwent a R1 resection and with a grade 3 STS; (3) adjuvant chemotherapy cannot rescue an inadequate initial surgery; (4) if selected, chemotherapy has to be contain anthracycline and fractionated adequate dose of ifosfamide (around 9 g/m(2) per cycle); (5) the era of adjuvant chemotherapy trials with the same chemotherapy regimen in all histological subtype of sarcoma is ended; and (6) prognosis of patients with a localized STS starts at diagnosis. The dramatic activity of imatinib in GIST, the heterogeneous outcome of each histological subtype of sarcomas akin to being different diseases, and the high sensitivity of some histological subtypes of sarcoma to specific agents clearly open a new era in the management and the evaluation of new agents in the field of STS. The design of the future adjuvant trials has to incorporate these new findings and new prognostic/predictive biomarkers in order to improve the as yet dismal prognosis of patients developing high-grade localized STS.