Abstract
BackgroundThe STAR-TReC trial is an international multi-center, randomized, phase II study assessing the feasibility of short-course radiotherapy or long-course chemoradiotherapy as an alternative to total mesorectal excision surgery. A new target volume is used for both (chemo)radiotherapy arms which includes only the mesorectum. The treatment planning QA revealed substantial variation in dose to organs at risk (OAR) between centers. Therefore, the aim of this study was to determine the treatment plan variability in terms of dose to OAR and assess the effect of a national study group meeting on the quality and variability of treatment plans for mesorectum-only planning for rectal cancer.MethodsEight centers produced 25 × 2 Gy treatment plans for five cases. The OAR were the bowel cavity, bladder and femoral heads. A study group meeting for the participating centers was organized to discuss the planning results. At the meeting, the values of the treatment plan DVH parameters were distributed among centers so that results could be compared. Subsequently, the centers were invited to perform replanning if they considered this to be necessary.ResultsAll treatment plans, both initial planning and replanning, fulfilled the target constraints. Dose to OAR varied considerably for the initial planning, especially for dose levels below 20 Gy, indicating that there was room for trade-offs between the defined OAR. Five centers performed replanning for all cases. One center did not perform replanning at all and two centers performed replanning on two and three cases, respectively. On average, replanning reduced the bowel cavity V20Gy by 12.6%, bowel cavity V10Gy by 22.0%, bladder V35Gy by 14.7% and bladder V10Gy by 10.8%. In 26/30 replanned cases the V10Gy of both the bowel cavity and bladder was lower, indicating an overall lower dose to these OAR instead of a different trade-off. In addition, the bowel cavity V10Gy and V20Gy showed more similarity between centers.ConclusionsDose to OAR varied considerably between centers, especially for dose levels below 20 Gy. The study group meeting and the distribution of the initial planning results among centers resulted in lower dose to the defined OAR and reduced variability between centers after replanning.Trial registrationThe STAR-TReC trial, ClinicalTrials.gov Identifier: NCT02945566. Registered 26 October 2016, https://clinicaltrials.gov/ct2/show/NCT02945566).
Highlights
The STAR-TReC trial is an international multi-center, randomized, phase II study assessing the feasibility of short-course radiotherapy or long-course chemoradiotherapy as an alternative to total mesorectal excision surgery
The STAR-TReC trial is an international multi-center, randomized, phase II study assessing the feasibility of short-course radiotherapy (SC-RT) or long-course chemoradiotherapy (LC-CRT) with subsequent two-stage response assessment as an alternative to total mesorectal excision (TME) surgery
This is a smaller clinical target volume (CTV) compared to the current standard for radiotherapy of rectal cancer and it is specially tailored for early stage disease, with the goal of organ preservation
Summary
The STAR-TReC trial is an international multi-center, randomized, phase II study assessing the feasibility of short-course radiotherapy or long-course chemoradiotherapy as an alternative to total mesorectal excision surgery. Complications of TME surgery include anastomotic leaks, urinary and fecal incontinence and sexual dysfunction. Research for this early stage rectal cancer patient group has focused on alternative strategies, such as limited resections and active surveillance of good responders after chemoradiotherapy [7,8,9,10]. The STAR-TReC trial is an international multi-center, randomized, phase II study assessing the feasibility of short-course radiotherapy (SC-RT) or long-course chemoradiotherapy (LC-CRT) with subsequent two-stage response assessment as an alternative to TME surgery. A novel target volume is used which includes only the mesorectum [12]
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