Demographics and tumor specific variables

A total of 5,664 patients underwent surgery alone (SA) without RT, 730 patients underwent neoadjuvant RT and surgery (NRT + S), and 1,091 underwent surgery and received adjuvant RT (ART + S). Patients had a mean age of 62.4 (± 13.2), 60.7 (± 12.6), and 60.9 (± 12.6) in the SA, NRT + S, and ART + S cohorts, respectively. Patients were predominately Caucasian in all three cohorts (SA: n = 4826, 85.2%, NRT + S: n = 621, 85.1%, ART + S: n = 899, 82.4%) and had a Charlson Deyo score of 0 (SA: n = 4329, 76.4%, NRT + S: n = 574, 78.6%, ART + S: n = 849, 77.8%). While the majority of patients were treated at academic medical centers (SA: n = 3324, 58.7%, NRT + S: n = 504, 69.0%, ART + S: n = 452, 41.4%), this did not necessarily correlate with high volume centers. Most patients were treated at centers that saw on average < 5 cases per year (SA: n = 4327, 76.4%, NRT + S: n = 498, 68.2%, ART + S: n = 1008, 92.4%). In addition, most patients had liposarcoma (SA: n = 3754, 66.3%, NRT + S: n = 392, 53.7%, ART + S: n = 534, 48.9%) and tumors > 10 cm (SA: n = 3390, 59.9%, NRT + S: n = 394, 53.9%, ART + S: n = 600, 54.9%). All demographic data can be found in Table 1.

Table 1 Comparison of no radiation, neoadjuvant radiation, and adjuvant radiation populationsUtilization of radiation therapy over time and survival analysis

Over time, the use of radiation therapy for the treatment of RPS decreased on average by < 1% per year (p = 0.018, Fig. 1A). Even though there was a decrease in RT, 24.5% of the population was still receiving RT in the most recent year of diagnosis (2017). There was also a shift from the use of adjuvant to neoadjuvant RT. On average, the use of neoadjuvant radiation therapy increased by 13% per year and the use of adjuvant radiation therapy decreased by 6% per year (p < 0.0001, Fig. 1B). There was no difference in overall survival comparing patients who received RT and surgery versus surgery alone (p = 0.0793, Fig. 2A). There was also no difference in overall survival among patients who received neoadjuvant versus adjuvant RT (p = 0.6899, Fig. 2B).

Fig. 1

A The overall use of radiation therapy has decreased over time. B There has been a shift from using adjuvant radiation therapy to neoadjuvant radiation therapy

Fig. 2

Survival analysis comparing. A Radiation therapy and surgery alone and B adjuvant and neoadjuvant therapy in patients with retroperitoneal sarcomas

Factors associated with receiving radiation therapy

On univariable analysis, age, sex, race, ethnicity, great circle distance, facility type, year of diagnosis, annual hospital volume, tumor differentiation, histology, tumor size, and tumor grade were each associated with receipt of RT and therefore, included in the multivariable analysis. On multivariable analysis, older patients (OR 0.984, CI 0.979–0.989, p < 0.0001) and patients treated at an academic/research program (OR 0.553, CI 0.384–0.797, p = 0.0015), comprehensive community cancer program (OR 0.648, CI 0.458–0.918, p = 0.0145), or integrated network cancer program (OR 0.577, CI 0.392–0.850, p = 0.0053) were less likely to receive radiation therapy compared to individuals treated at a community cancer program. In addition, patients with a later year of diagnosis were less likely to receive RT (OR 0.964, CI 0.933–0.997, p = 0.0308). Compared with patients who had well differentiated tumors, individuals with moderately differentiated tumors (OR 1.639, CI 1.1262–2.127, p = 0.0002), poorly differentiated tumors (OR 1.820, CI 1.451–2.283, p < 0.0001), or undifferentiated tumors (OR 1.665, CI 1.263–2.194, p = 0.0003) were associated with receipt of radiation therapy (Table 2). Patients with liposarcomas (OR 0.762, CI 0.615–0.857, p = 0.0002) compared to leiomyosarcoma and patients with larger tumors > 10 cm (OR 0.795, CI 0.684–0.923, p = 0.0026) were less likely to receive RT as shown in Table 3.

Table 2 Comparison of neoadjuvant radiation and adjuvant radiation populationsTable 3 Multivariable analysis for factors associated with receiving any type of radiation therapyFactors associated with receiving neoadjuvant radiation therapy

On univariable analysis, sex, ethnicity, great circle distance, facility type, year of diagnosis, annual hospital volume, tumor differentiation, tumor size, and tumor grade were all associated with receipt of neoadjuvant RT and included on the multivariable analysis (univariable analysis in Table 2). Histology was included on multivariable analysis for clinical significance. On multivariable analysis, male patients (OR 1.371, CI 1.066–1.762, p = 0.014) and traveling from further away (great circle distance OR 1.005, CI 1.001–1.010, p = 0.024) were associated with receiving neoadjuvant RT. Patients treated at academic/research programs (OR 6.162, CI 2.531–15.001, p < 0.0001) or integrated network cancer program (OR 4.261, CI 1.405–12.924, p = 0.011) compared to a community cancer program and treated at hospitals with an average of > 10 cases/year (OR 14.795, CI 6.058–36.136) compared to hospitals with < 5 cases/year were associated with receiving neoadjuvant RT over adjuvant RT. Patients with liposarcomas (OR 0.574, CI 0.409–0.805, p = 0.001) compared to leiomyosarcoma was associated with receiving adjuvant RT. Larger tumor size (> 10 cm, OR 2.009, CI 1.477–2.733, p < 0.0001) was associated with receiving neoadjuvant over adjuvant RT. The results of multivariable analysis are noted in Table 4.

Table 4 Multivariable analysis for factors associated with receiving neoadjuvant radiation therapy compared to adjuvant radiation therapy