RTOG 0933 reported significant benefit in memory preservation and quality of life as compared to historical controls in using hippocampal-avoidance whole brain radiation therapy (HA-WBRT) in the treatment of multiple brain metastases (1). With the publication of the NRG CC001 randomised trial showing better preservation of cognitive function and patient-reported symptoms with no difference in intracranial progression or overall survival, HA-WBRT with memantine is now established as a new standard of care for treatment of multiple brain metastases (2). However, the planning aspect is significantly...

10 patient datasets were contoured by 3 radiation oncologists following the RTOG atlas and inter-clinician conformality was assessed using the Dice co-efficient for overlap and Hausdorff maximal and average distances for variability. Auto-contours were generated for the same 10 patient datasets in Elements TPS and compared against all radiation oncologists’ contours. The RTOG-based clinician and MRI-atlas based Elements auto-contours were then compared to those of a neuroradiologist’s.

The manual contours by the radiation oncologists had reasonable conformality with each other with an average Dice co-efficient of 0.766 for both the left and right hippocampi. Hausdorff maximum distance was 4.8mm for the left hippocampus and 5.2 mm for the right hippocampus. [Fig 1] [Fig 2] When comparing Elements auto-contours with clinician contours, there was less spatial overlap with a lower average Dice co-efficient of 0.537 for the left hippocampus and 0.574 for the right. Average maximum Hausdorff distance was almost double that between...

The current results show reasonable conformality of clinician manual contouring using the RTOG Atlas. Differences in clinician contours when compared with neuro-radiologist contours may be due to differences in RTOG-atlas guidelines adhered to by clinicians compared to a more anatomy-based contouring by the neuroradiologist. Whilst Elements TPS could be utilized as a starting point, contours will require modification by clinicians to conform to the RTOG atlas. Future study into other auto-contouring systems and contouring by radiation therapists after training will be undertaken.

Gondi V, Pugh S, Tome WA, et al. Preservation of Memory With Conformal Avoidance of the Hippocampal Neural Stem-Cell Compartment During Whole-Brain Radiotherapy for Brain Metastases (RTOG 0933): A Phase II Multi-Institutional Trial. J Clin Oncol. 2014 Oct 27; 32(34): 3810-3816. Brown PD, Gondi V, Pugh S, et al. Hippocampal Avoidance During Whole-Brain Radiotherapy Plus Memantine for Patients With Brain Metastases: Phase III Trial NRG Oncology CC001. J Clin Oncol. 2020 Apr 1; 38(10): 1019-1029. Gondi V, Tome WA, Rowley H, et al. Hippocampal contouring:...