Trends in multi-lesion stereotactic radiosurgery: an IROC survey on the state of the practice.

PURPOSE: The last decade has seen an increase in the treatment of multiple lesions within a single course of stereotactic radiosurgery (SRS). Hardware, software, and processes have evolved to support the clinical adoption of multi-lesion SRS. An understanding of the current state of the practice is needed to provide proper guidance.

METHODS

The Imaging and Radiation Oncology Core (IROC) distributed an addendum on SRS practices along with its annual facility questionnaire. Participants were asked 13 questions regarding their SRS program, including: whether single-isocenter multiple target deliveries are performed, delivery equipment used, the maximum number of lesions treated with a single isocenter, quality assurance practices, and the margins used for treatment.

RESULTS

The survey generated 879 responses from institutions with an SRS program. Among those programs, 91% (n=789) reported treating multiple lesions within a single course of treatment. Among institutions with equipment capable of treating multiple lesions with a single isocenter, 83% (n=504) reported doing so. Practices varied across clinical programs; for example, expansion margins from gross tumor volume (GTV) to planning target volume (PTV) ranged from 0mm to 2+mm. This variation was partially associated with the use of a six degree-of-freedom (6DOF) couch and the maximum number of lesions treated in a single isocenter. Among programs that treated multiple lesions per isocenter, 84.1% used a 6DOF couch compared to only 50.8% that treated one lesion per isocenter (p<0.01, χ2=64.8). Similarly, among institutions that reported no GTV to PTV margin (n=79), 100% used a 6DOF couch while only 55.3% of institutions that used a 2 mm margin reported the use of a 6DOF couch (p<0.01, χ2=73.0).

CONCLUSION

Treatment of multiple lesions in a single course of SRS has become standard practice. However, when treating with a single isocenter, variability exists in clinical practice, highlighting the need for guidance on best practices.