Adjuvant Radiotherapy Improves Survival in Rare Sarcoma Subtype

Adjuvant radiotherapy (RT) was associated with improved survival for patients with non-retroperitoneal abdominal soft tissue sarcomas (NRA-STS), but the addition of chemotherapy did not confer a similar survival benefit. The results, produced from an analysis of data collected in the National Cancer Data Base, were published in the Asia-Pacific Journal of Clinical Oncology.

At 49 months’ median follow-up, RT was associated with an improved 5-year overall survival compared with surgery alone (52% vs 46%; P = .009), with a 29% reduction in risk for death.

“Our provocative analysis hints to the need of radiotherapy incorporation in the management of NRA-STS and preferably to higher radiation dose employing a precise sparing radiotherapy technique,” concluded lead author William Ross Green, MD, Department of Radiation Oncology, Rutgers Robert Wood Johnson Medical School, and fellow researchers.

“It also points to the need to large-scale multi-institutional randomized studies to elucidate the role of chemotherapy and radiotherapy in the management of this disease entity and to guide practitioners on the optimum paradigm to integrate these modalities in relation to surgery.”

Non-retroperitoneal abdominal soft tissue sarcomas is a rare subset of a rare condition. Soft tissue sarcomas represent just 1% of adult cancers; NRA-STS makes up 10% to 20% of STS diagnoses. NRA-STS represented 8.3% of STS diagnoses in this analysis.

The disease displays high local recurrence rates with a resultant low overall survival. Treatment generally includes surgical resection with negative surgical margins, but there is little randomized trial data supporting an ideal treatment regimen. Traditionally, physicians have used adjuvant RT to reduce local failure, and a brachytherapy dose of 42 Gy to 45 Gy has been used to reduce local recurrence rates compared with surgery alone.

Green et al conducted this retroactive analysis comparing surgery and RT with surgery alone and comparing surgery and chemotherapy with surgery alone to determine the usage pattern and survival benefit associated with adjuvant therapy.

From 2004 to 2013, 2832 patients underwent surgery for nonmetastatic NRA-STS, according to the National Cancer Data Base. Five-year survival was superior in patients who received perioperative radiotherapy (HR, 0.75; 95% CI, 0.71-0.78) compared with surgery alone (HR, 0.46; 95% CI, 0.43-0.49).

Outcomes with the addition of adjuvant chemotherapy (HR, 0.46; 95% CI, 0.39-0.54) were similar to results with surgery alone (HR, 0.45; 95% CI, 0.42-0.49)

Univariate analysis showed that male gender, age older than 50 years, comorbidity, tumor larger than 8 cm, positive surgical margins, not receiving perioperative RT and/or receiving an RT dose less than 60 Gy as poor prognostic factors for survival. Those results were consistent on multivariate analysis for all factors except for gender and RT dose covariates.

Propensity score model accounting for age, comorbidity, tumor size, margin status, and chemotherapy use matched 377 patients receiving adjunctive radiotherapy with 377 control patients to reduce the imbalance of covariates across comparison groups. Researchers observed a significant 5-year survival advantage with RT in this population as well (52% vs 46%; P = .009).

The Univariate and multivariate models identified radiotherapy administration, age younger than 50 years, absence of comorbidity, negative surgical margins and smaller tumor size as favorable significant prognostic factor for survival.

Radiation dose <60 Gy showed a trend toward inferior survival. On univariate analysis, RT dose >60 Gy was also associated with a decreased risk for death (HR, 0.54; 95% CI, 0.32-0.89). However, this factor only trended toward significance on multivariate analysis (P = .06).

Positive margins were detected in 455 patients and were not correlated with tumor size. Margin positivity decreased 5-year survival by 19%, from an HR of 0.54 (95% CI, 0.49-0.58) to an HR of 0.35 (95% CI, 0.3-0.4). The use of radiotherapy in the presence of positive margins was associated with reduced mortality (HR, 23%; 95% CI, 0.59-0.97).

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