Top Line: Is there a standard, reproducible way to build intentional hotspots into VMAT lung SBRT plans?
The Study: Back in the day, 3D-conformal and dynamic conformal arc SBRT plans naturally produced intratumoral hotspots. Modern VMAT can easily eliminate that dose heterogeneity if the planner isn't careful, potentially sacrificing a biological advantage. This technical report describes the “SPICE” (Stereotactic Planning with Intentional Central Escalation) approach to deliberately reintroduce dose heterogeneity. All patients were treated on a conventional LINAC with FFF beams (6 or 10 MV), typically with two partial VMAT arcs. Common prescriptions were 50 Gy/5, 48 Gy/4, or 34 Gy/1, with OAR constraints per RTOG 0813/0915. The contouring framework centered on a novel structure: the Definitive Target Volume (DTV). After defining the IGTV, all nearby OARs received a uniform 3 mm PRV expansion, and this PRV was subtracted from the IGTV to create the DTV. They used three planning tiers. Extra SPICE was the most aggressive where the entire DTV was uniformly escalated to at least 120% of Rx dose, with Dmax kept below 150%. This was preferred when no OARs were in the neighborhood. Regular SPICE (the workhorse tier) placed a focal hotspot within the DTV with Dmax exceeding 115%-120% of the Rx. Non-SPICE planning kept things homogeneous (Dmax < 110%, ideally < 107.5%, with Dmax confined to the IGTV) and was reserved for ultracentral tumors. All of these specifically respected OAR dose limits over supratherapeutic DTV doses.
TBL: SPICE is a systematic, tiered approach to strategically placing hotspots with lung tumors during lung SBRT in order to gain a little extra BED without risking toxi..ahem, adverse effects to organs at risk. | Johnson, Pract Radiat Oncol 2026
The Study: Back in the day, 3D-conformal and dynamic conformal arc SBRT plans naturally produced intratumoral hotspots. Modern VMAT can easily eliminate that dose heterogeneity if the planner isn't careful, potentially sacrificing a biological advantage. This technical report describes the “SPICE” (Stereotactic Planning with Intentional Central Escalation) approach to deliberately reintroduce dose heterogeneity. All patients were treated on a conventional LINAC with FFF beams (6 or 10 MV), typically with two partial VMAT arcs. Common prescriptions were 50 Gy/5, 48 Gy/4, or 34 Gy/1, with OAR constraints per RTOG 0813/0915. The contouring framework centered on a novel structure: the Definitive Target Volume (DTV). After defining the IGTV, all nearby OARs received a uniform 3 mm PRV expansion, and this PRV was subtracted from the IGTV to create the DTV. They used three planning tiers. Extra SPICE was the most aggressive where the entire DTV was uniformly escalated to at least 120% of Rx dose, with Dmax kept below 150%. This was preferred when no OARs were in the neighborhood. Regular SPICE (the workhorse tier) placed a focal hotspot within the DTV with Dmax exceeding 115%-120% of the Rx. Non-SPICE planning kept things homogeneous (Dmax < 110%, ideally < 107.5%, with Dmax confined to the IGTV) and was reserved for ultracentral tumors. All of these specifically respected OAR dose limits over supratherapeutic DTV doses.
TBL: SPICE is a systematic, tiered approach to strategically placing hotspots with lung tumors during lung SBRT in order to gain a little extra BED without risking toxi..ahem, adverse effects to organs at risk. | Johnson, Pract Radiat Oncol 2026