Long-term Oncologic Outcomes After Neoadjuvant Radiation Therapy for Retroperitoneal Sarcomas.

Retroperitoneal sarcomas (RPSs) require multidisciplinary care, yet they often represent a therapeutic dilemma because of the heterogeneous nature of their biology, behavior, and natural history. Characterized by multiple histologic subtypes—the most common being liposarcoma (40%) and leiomyosarcoma (25%)—median survival ranges from approximately 3 to 12 years for high- and low-grade tumors, respectively.1 After tumor grade, the most important factor impacting survival is extent of resection, as incomplete resection is associated with a 70% higher risk of death.2 However, negative margins are often difficult to achieve, especially in large tumors that encroach on vital organs or other structures, and incomplete resection occurs in up to one-fifth of operations.2,3 There are several hypothetical benefits for the use of neoadjuvant radiation therapy (RT) in patients with RPSs. As compared with adjuvant RT, administration of radiation in the preoperative period may allow the radiation oncologist to better define the target volume so that the RT can be focused on the tumor rather than the adjacent normal structures. If RT is delivered after surgery, the adjacent normal structures frequently fall into the postoperative tumor bed, which can limit the radiation dose to the target and increase the amount of radiation to normal structures. This may be a particular concern for bowel, which can become fixed as a consequence of fibrosis and adhesions, so that the same segment of bowel receives daily radiation during adjuvant RT.3,4 In addition, several studies have suggested that preoperative RT may improve short-term oncologic outcomes (eg, tumor resectability and achievement of negative margins) in retroperitoneal and other soft tissue sarcomas.5 Finally, there is some evidence that preoperative RT may decrease locoregional recurrence.5–8 Unlike extremity sarcoma, mortality among patients with RPSs is often secondary to local recurrence rather than distant metastasis.9 Thus, it is conceivable that improvements in local control may translate to increases in overall survival, although this remains widely debated.5–8 Notably, a randomized controlled trial evaluating the efficacy of neoadjuvant RT in the treatment of RPS has never been completed. In 2006, the American College of Surgeons Oncology Group had to terminate its phase 3 trial Z9031 because of inadequate patient accrual. Eight years later, efforts are underway by the European Organisation for Research and Treatment of Cancer (EORTC) to recruit patients for a similar, multicenter trial (EORTC 62092-22092).10 However, even if accrual is successful, results are still years away. The National Cancer Data Base (NCDB) is administered by the American College of Surgeons together with the American Cancer Society and at present contains data from more than 1500 cancer institutions including more than 30 million patients.11 The Commission on Cancer estimates that the NCDB captures approximately 70% of all cancer diagnoses in the United States.11 Thus, the NCDB is a particularly valuable tool for evaluating rare malignancies in which highly specialized treatment modalities are offered only at select institutions. The purpose of this study was to utilize the NCDB to evaluate long-term oncologic outcomes associated with neoadjuvant RT for RPSs.