A Survey of Liver Stereotactic Body Radiation Therapy Practice Patterns in the United States

Abstract

Although stereotactic body radiotherapy (SBRT) has shown promising results in liver tumors, little is known about its usage in clinical practice. A survey was performed among US radiation oncologists, with results regarding SBRT adoption reported elsewhere (Pan, Cancer 2011). This study presents further analysis of prescriptions, fractionation, and fiducial marker (FM) usage in liver SBRT from that survey. A random sample of 1600 US radiation oncologists was surveyed regarding SBRT usage. Physicians were asked about their practice (type, size, and location), years in practice, years of SBRT experience, use of FM and body frame, target localization techniques, motion management, and most common prescription. A biological equivalent dose (BED) was calculated using the linear quadratic model with α/β = 10. Chi-square tests were performed to identify differences in fractionation and dose per fraction. Spearman's rank correlation coefficients (rs) were calculated to identify associations with BED and FM usage. Of the 1600 physicians surveyed, 40% of contactable physicians responded; 64% of evaluable respondents used SBRT, of which 55% treated liver. Of liver SBRT users, 141 (89%) supplied their most common prescription. The reported prescriptions were varied, with the most common being 15 Gy x 3 (19%), 10 Gy x 5 (14%), and 20 Gy x 3 (12%). The most common number of fractions used was 3 (48%), 5 (38%), and 4 (9%). Practice type, use of body frame and FM, years of SBRT experience, and target localization techniques were not associated with significant differences in fractionation. The median dose per fraction among all prescriptions was 12 Gy. A fraction size of ≥15 Gy for liver SBRT was reported more frequently by respondents who adopted SBRT at any disease site earlier (2000-2008) as compared to more recently (2009-2010) (48% vs 32%, p = 0.02). = The median BED was 106 Gy (12 Gy x 4), including 12% of respondents who treated with BED of 180 Gy (20 Gy x 3). The use of body frame (rs = 0.20, p = 0.02), and practice in an academic center (rs = 0.20, p = 0.02) were associated with higher BED, while increased number of fractions (rs: -0.41, p<0.001) and additional years in practice (rs: -0.17, p = 0.04) were associated with lower BED. Of liver SBRT users, 57% reported the use of FM. Rank correlation identified the use of planar imaging (rs = 0.27, p = 0.001) and gating for motion management (rs = 0.20, p = 0.03) as positively associated with FM usage, while the use of a body frame (rs: -0.18, p = 0.03) had a negative association. There is wide variation in prescription patterns among US radiation oncologists for liver SBRT, with no single prescription accounting for more than a fifth of responses. Further study is required to ascertain optimal dose and fractionation schemes in liver SBRT.