ESTRO 2026 congress report
 

Report by the ESTRO Lower GI Focus Group

At ESTRO 2026, the lower GI track showed just how fast this field is moving. In rectal and anal cancer, the discussion is no longer simply about escalation or de-escalation. It is about personalisation: preserving organs when possible, selecting patients more accurately, integrating advanced imaging, and measuring value not only through oncological outcomes, but also through quality of life and patient-reported outcomes.

Rectal cancer: organ preservation as a clinical strategy

One of the strongest threads across the congress was the shift from standardised pathways to risk-adapted and response-adapted treatment. In rectal cancer, organ preservation is increasingly being framed as a realistic endpoint for selected patients, supported by better staging, multidisciplinary decision-making, and more refined radiotherapy strategies.

The debate around preservation made clear that radiotherapy, surgery—including trans-anal excision—chemotherapy, and immunotherapy should not be seen as competing silos, but as components of a more selective and individualised treatment landscape. Tumour board sessions reinforced a central message: intensification and organ-sparing approaches now need to be judged not only by response rates, but also by durability, bowel function, and patient experience.

This connects with a broader evolution in target definition and treatment delivery. As the first study to prospectively explore mesorectum-only irradiation as part of an organ-preservation strategy, STAR-TREC helped establish a new direction for volume-adapted radiotherapy: smaller volumes, smarter escalation, and better integration with systemic or immune-based approaches. At the same time, the growing emphasis on MRI-based target definition and adaptive workflows reflects how technical precision is becoming inseparable from clinical ambition.

Sessions on individualised treatment of primary rectal cancer reinforced another important point: better patient selection begins with better interpretation. Updated imaging guidance, including the distinction between rectal and sigmoid tumours using the sigmoid take-off, is not a technical detail; it directly shapes treatment choices. The same applies to sequencing. Total neoadjuvant treatment continues to push systemic therapy earlier, but the real shift is conceptual: surgery is no longer the automatic endpoint for every patient.

This was especially visible in presentations on MRI-guided adaptive dose escalation, where the focus was not only on feasibility, but also on how to identify poor responders early and intensify treatment in a biologically meaningful way, as shown in studies such as MARS and THUNDER-2.

In locally recurrent rectal cancer, the upcoming ESTRO guidelines highlight the complexity of reirradiation. The message was measured but important: reirradiation is feasible, but only with rigorous individualisation, careful attention to cumulative dose, advanced planning techniques, and, ideally, treatment in expert centres. This is a reminder that innovation in lower GI oncology is also about safe salvage.

The APHRODITE trial, presented by Ane Appelt, added another important piece to the organ-preservation discussion: how best to treat patients who are not candidates for upfront surgery, including elderly and frail patients. Risk-adapted radiotherapy with mesorectum-only irradiation and tumour dose escalation improved 6-month clinical complete response in early rectal cancer, while underlining that toxicity, quality of life, and bowel function are essential to defining the true value of preservation strategies.

Anal cancer: PLATO and risk-adapted radiotherapy

In anal cancer, the PLATO trials stood out as one of the clearest examples of radiotherapy moving away from a one-size-fits-all model. The PLATO platform provides a risk-adapted framework across disease stages. ACT3 supports local excision plus selective low-dose chemoradiotherapy for early margin-positive disease, with excellent compliance and acceptable toxicity. ACT4 shows that reduced-dose IMRT in early anal cancer achieves strong 3-year locoregional control with similar patient-reported late toxicity, supporting de-escalation as a patient-friendly option. ACT5 explores dose escalation for locally advanced disease, but early results do not yet show improved complete response or patient-reported outcome benefit, with further follow-up needed before changing practice.

Overall, the main takeaway from ESTRO 2026 is clear: lower GI is becoming one of the most sophisticated areas in radiation oncology because it is learning to be more selective. More adaptation, more integration, more attention to function, and a stronger commitment to understanding benefit from the patient’s perspective—that is where the field is moving. And it is moving fast.

#ESTRO26 #RadiationOncology #RectalCancer #AnalCancer #OrganPreservation #RiskAdaptiveRadiotherapy #PatientReportedOutcomes

 

 

Letizia Deantonio, MD
Senior consultant, Radiotherapy Clinic, Oncology Institute of Southern Switzerland, EOC
Faculty of Biomedical Sciences, Università della Svizzera Italiana
Switzerland
letizia.deantonio@eoc.ch
ESTRO Lower GI Focus Group Member