2.0 b10a5c9d-2005-4b10-816f-350beee67788 *AOS_Rectum hypofx 25/20Gy 5fx SIB v1 Pelvis Rectum *AOS_Rectum hypofx 25/20Gy 5fx SIB AOS sample template - to be copied, reviewed, modified as deemed appropriate, and approved by site physicist Summary: 5fx pre-op rectum to 25/20 Gy SIB Reference: Myerson et al, "Five fractions of radiation therapy followed by 4 cycles of FOLFOX chemotherapy as preoperative treatment for rectal cancer", Int J Radiat Onc Biol Phys 2014:88(4);829-836. Version 1.3 Created: 2/23/2025 (PHH) Last updated: 4/18/2025 (PHH) - Corrected OAR label (Bowel_Small) ********************************************************************* Rx: "Two nested target volumes receiving a total of 20 and 25 Gy in... 5 fractions... (with) at least 95% of the PTV (must) be covered by 95% of the prescription dose. Maximum allowed dose was 115% of prescription." - Myerson et. al Contouring: "The clinical target volume 20 Gy (CTV20Gy) was an elective nodal target volume defined by the Radiation Therapy Oncology Group (RTOG) guidelines (31). CTV25Gy included the rectum and the mesorectal compartment over the length of involved rectum with a 1-cm margin cephalad and caudad. If CTV25Gy extended into the distal rectum, its lateral borders included the full thickness of the sphincteric musculature. Any clinically positive nodal regions within the pelvis were also included within CTV25Gy, including the mesorectum with involved perirectal nodes. If involved perirectal nodes continued more than 1 cm cephalad or caudad to the primary tumor, then the mesorectal coverage was appropriately extended."- Myerson et. al Margins: Paraphrasing the 'Methods' section of Myerson et. al: CTV_20 = elective nodal target volume consistent with RTOG guidelines. CTV_25 = rectum and mesorectal compartment over the length of involved rectum with a 1.0 cm margin cephalad and caudad, and any clinically positive nodal regions within the pelvis. PTV_20 = CTV_20 plus 0.5 cm margin PTV_25 = CTV_25 plus 0.5 cm margin * note that a smaller PTV expansion that accounts for machine uncertainty and interfraction motion should be considered for daily online adaptive treatment. OAR Constraints: "Normal tissue constraints were that small bowel be kept below an absolute maximum of 25 Gy and that volume at or above 20 Gy (V20Gy) be kept as small as possible for small bowel (preferably <50 cc), uninvolved large bowel (defined as large bowel lying outside CTV20Gy), and femoral heads. Bowel was contoured tightly, as described in the RTOG normal tissue guidelines (32)." Constraints for Femur_L, Femur_R and Bowel_Large-CTV_20 are based on clinical judgment consistent with Myerson's statement that "volume at or above 20 Gy (V20Gy) be kept as small as possible". Myerson did not include a constraint for Bladder. This was added based on clinical judgment, with Priority = 3. Structures have been named according to TG 263. 7200 FMA 3.2 Small bowel 4278222976 Bowel_Small 15900 FMA 3.2 Urinary bladder 4294967040 Bladder 32842 FMA 3.2 Femur head & neck right 4294934528 Femur_R 32843 FMA 3.2 Femur head & neck left 4278190208 Femur_L 7201 FMA 3.2 Large bowel 4290536451 Bowel_Large R-429EC SRT Planning target volume 4294901760 PTV_20 Target2 R-429EB SRT Clinical target volume 5 Target3 R-429EB SRT Clinical target volume 5 Body BODY 99VMS_STRUCTCODE 1.0 Body plus other external items -5 ]]> R-429EB SRT Clinical target volume 4280918220 CTV_20 R-429EB SRT Clinical target volume 4280918220 CTV_25 R-429EC SRT Planning target volume 4294901760 PTV_25 Target3 R-429EB SRT Clinical target volume 5 Body BODY 99VMS_STRUCTCODE 1.0 Body plus other external items -5 ]]> NormalTissue 99VMS_STRUCTCODE 1.0 Unidentified structure 4291864166 Bowel_Large-CTV_20 OAR5 7201 FMA 3.2 Large bowel Target2 R-429EB SRT Clinical target volume Body BODY 99VMS_STRUCTCODE 1.0 Body plus other external items -5 ]]> Target1 4 VolumeDose ShouldBeMoreOrEqual 95 Relative 20 Absolute 1 2 Target4 5 VolumeDose ShouldBeMoreOrEqual 95 Relative 25 Absolute 1 1 DoseVolume ShouldBeLessOrEqual 0.03 Absolute 115.00000000000001 Relative 3 3 OAR1 VolumeDose ShouldBeLess 50 Absolute 20 Absolute VolumeDose ShouldBeLessOrEqual 100 Absolute 20 Absolute 2 1 OAR1 DoseVolume ShouldBeLess 0.03 Absolute 25 Absolute 3 2 OAR1 MeanDose OAR2 VolumeDose ShouldBeLessOrEqual 50 Relative 25 Absolute 3 1 OAR2 MeanDose OAR3 VolumeDose ShouldBeLessOrEqual 10 Relative 20 Absolute VolumeDose ShouldBeLessOrEqual 25 Relative 20 Absolute 3 4 OAR4 VolumeDose ShouldBeLessOrEqual 10 Relative 20 Absolute VolumeDose ShouldBeLessOrEqual 25 Relative 20 Absolute 3 5 ControlRegion1 VolumeDose ShouldBeLessOrEqual 50 Absolute 20 Absolute VolumeDose ShouldBeLessOrEqual 100 Absolute 20 Absolute 2 2 ControlRegion1 MeanDose OAR5 MeanDose NoNormalization 1 None 1 None 1 None 1 None 1 None