S3038
Invited Speaker
ESTRO 2026
• ACT3: to assess 3-year locoregional failure free rate in participants with anal margin tumours treated with local excision. • ACT4: to a ssess 3-year locoregional failure free rate in participants with early-stage disease. • ACT5: o Pilot phase: to assess acute toxicity rates and treatment compliance within each of the treatment arms. o Phase II: to assess acute toxicity data to determine which arms will be taken forward to phase III. o Phase III: to assess 3-year locoregional failure-free rates and locoregional failure free survival at 3 years post- recruitment, in participants with locally advanced disease. Currently, the results of ACT5 are immature but there is much to learn from the early pilot and early outcome data; those of ACT4 (2) and ACT3 are already informing clinical practice and subject to a current impact assessment. The platform has provided the first trials to integrate and report using the validated EORTC QLQ-ANL27 anal cancer specific Patient Reported Outcome Measures tool and provide insights relating to differing stages of disease and treatment approaches and their impacts on patients. Critically the foreground work and delivery have informed practice alongside the actual trial outcomes, which will be discussed and whilst translational research is ongoing, it is already shedding light on some important areas for future impact.
Units and reduce the reliability of CBCT for dose calculation. Understanding these limitations is a first step in identifying the requirements for better reconstruction techniques. We will then move to the current state of CBCT image quality as provided by commercial systems, looking at both recent improvements and remaining gaps. Different strategies that have been explored to enhance quantitative performance will be discussed, including physics-based corrections, and algorithmic improvements in reconstruction. Furthermore, methods aimed at reducing artifacts and improving HU consistency will be discussed. Finally, the lecture will explore several promising research directions that aim to further improve CBCT image quality and HU robustness, thereby moving towards conventional CT performance. These include advanced scatter correction techniques, dual-energy approaches, and the application of artificial intelligence for image reconstruction and artifact reduction. Together, these developments have the potential to significantly improve image quality and quantitative accuracy, expanding the possibilities for CBCT-based (online) adaptive workflows in the near future, and possibly allow better treatment follow up and radiomics type analyses further in the future as well. 5434 What has PLATO contributed to the treatment of anal cancer to date? Richard A Adams Centre for Trials Research, Cardiff University, Cardiff, United Kingdom. Oncology, Velindre Cancer Centre, Cardiff, United Kingdom The UK Platform Trial for anal cancer "PLATO" (1) builds on a long tradition of national trials pivotal to the optimal treatment of anal cancer. Having commenced recruitment in 2017 "PLATO" attempts to
answer clinical questions in relation to the management of localised anal cancer with
radiotherapy across a spectrum of stages from early (T1N0) to locally advanced (T3/4, any N+). The platform incorporates three trials ACT3, ACT4 and ACT5. • PLATO ACT3 is the first multi-centre phase II study to assess low dose chemoradiotherapy in early margin positive anal carcinoma. • PLATO ACT4 is the first ransomised phase II study to assess IMRT dose de-escalation in early anal carcinoma. • PLATO ACT5 is the first randomised phase II/III study to assess IMRT dose escalation in advanced anal carcinoma. The primary objectives are as follows:
References: (1) Frood R, et al Personalising anal cancer radiotherapy dose (PLATO): protocol for a multicentre integrated platform trial. BMJ Open. 2025 Nov 9;15(11):e109655. doi: 10.1136/bmjopen-2025-109655. PMID: 41213708; PMCID: PMC12658545. (2) Gilbert A, et al PLATO trial study group. Standard versus reduced-dose chemoradiotherapy in anal cancer (PLATO-ACT4): short-term results of a phase 2 randomised controlled trial. Lancet Oncol. 2025 Jun;26(6):707-718. doi: 10.1016/S1470-2045(25)00213- X. Epub 2025 May 4. PMID: 40334666.
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