Pelvic normal tissue contouring guidelines for radiation therapy: a Radiation Therapy Oncology Group consensus panel atlas

Abstract

Purpose: To define a male and female pelvic normal tissue contouring atlas for Radiation Therapy Oncology Group (RTOG) trials.

Methods and materials: One male pelvis computed tomography (CT) data set and one female pelvis CT data set were shared via the Image-Guided Therapy QA Center. A total of 16 radiation oncologists participated. The following organs at risk were contoured in both CT sets: anus, anorectum, rectum (gastrointestinal and genitourinary definitions), bowel NOS (not otherwise specified), small bowel, large bowel, and proximal femurs. The following were contoured in the male set only: bladder, prostate, seminal vesicles, and penile bulb. The following were contoured in the female set only: uterus, cervix, and ovaries. A computer program used the binomial distribution to generate 95% group consensus contours. These contours and definitions were then reviewed by the group and modified.

Results: The panel achieved consensus definitions for pelvic normal tissue contouring in RTOG trials with these standardized names: Rectum, AnoRectum, SmallBowel, Colon, BowelBag, Bladder, UteroCervix, Adnexa_R, Adnexa_L, Prostate, SeminalVesc, PenileBulb, Femur_R, and Femur_L. Two additional normal structures whose purpose is to serve as targets in anal and rectal cancer were defined: AnoRectumSig and Mesorectum. Detailed target volume contouring guidelines and images are discussed.

Conclusions: Consensus guidelines for pelvic normal tissue contouring were reached and are available as a CT image atlas on the RTOG Web site. This will allow uniformity in defining normal tissues for clinical trials delivering pelvic radiation and will facilitate future normal tissue complication research.

Fig. 1

Highlights from the Radiation Therapy Oncology Group (RTOG) male pelvis normal tissue atlas: sagittal view (A), coronal view (B), and axial views (C). The full atlas is available on the RTOG Web site. GI = gastrointestinal; GU = genitourinary; MRI = magnetic resonance imaging; PTV = planning target volume.

Fig. 1

Highlights from the Radiation Therapy Oncology Group (RTOG) male pelvis normal tissue atlas: sagittal view (A), coronal view (B), and axial views (C). The full atlas is available on the RTOG Web site. GI = gastrointestinal; GU = genitourinary; MRI = magnetic resonance imaging; PTV = planning target volume.

Fig. 2

Highlights from the Radiation Therapy Oncology Group (RTOG) female pelvis normal tissue atlas: sagittal view (A), coronal view (B), and axial views (C). The full atlas is available on the RTOG Web site. GI = gastrointestinal; GU = genitourinary; GYN = gynecologic; PTV = planning target volume.

Fig. 2

Highlights from the Radiation Therapy Oncology Group (RTOG) female pelvis normal tissue atlas: sagittal view (A), coronal view (B), and axial views (C). The full atlas is available on the RTOG Web site. GI = gastrointestinal; GU = genitourinary; GYN = gynecologic; PTV = planning target volume.

Fig. 3

Variability and difficulty in contouring ovaries. Five experts contoured the ovaries more round and inferior (A) compared with six experts whose contours were more superior and elongated (B). It should be noted that in the final version of the atlas, the ovaries and fallopian tubes comprise the adnexa (Adnexa_R and Adnexa_L) and correlate with the contours in B, whereas the contours in A were not deemed part of the adnexa in the final version.