Session Item

RTQA practice is known to have significant variation amongst institutions worldwide. It is critical to maintaining patient safety, treatment effectiveness and accuracy. However there is no standard practice, with often only target volume delineation reviewed alone and performed retrospectively. Previous studies have highlighted higher rates of changes made in more complex techniques and subsites. This study aims at evaluating our prospective structured peer review process in a proton beam therapy (PBT) centre.

We reviewed the RTQA cases of all patients treated at The Christie Proton Beam Centre since its opening in November 2018 until February 2021. The RTQA process is carried out weekly, is subsite specific and every case has their target volumes and plans reviewed in detail in the presence of consultants, fellows, physicists and dosimetrists. Since the COVID-19 pandemic, the peer review meetings are now virtual. Every peer review has a standardised RTQA form filled. We classified the peer reviews as having major/minor or no change. A major change was one where the target volumes (GTV and/or CTV) were too small or big; dose fractionation was incorrect to that of the prescription treated and any plan that was changed.  A minor change was one where there were minor modifications to the target volumes, OARs or non-essential suggestions in relation to the plan that didn’t result in the plan being altered eg. addition of an OAR.

There was a total of 1,209 peer reviews for 462 patients. 100% of cases had both volumes and plans peer reviewed prospectively. 591 were reviews of target volumes and 618 were plan reviews. In total there were 208 (17%) major changes, 194 (16%) minor and 807 (67%) with no changes. Of the major changes 137 (66%) were target volumes and 71 (34%) plans. Of the minor changes 174 (90%) were target volumes and 20 (10%) plans. There were more major and minor changes in the brain and head & neck subsites possibly due to their complexity. When diagnoses in the brain were categorised (Table 1) and reviewed against changes using a chi-squared test the resulting p-value = 0.027 suggests a significant relationship between type of diagnoses and likely need for change following peer review.

Target volume delineation and radiotherapy plans particularly in brain, head & neck as well as other complex subsites require mandatory prospective review as highlighted above. We have shown this to be practically achievable and successful despite challenging times.