In May in Vienna, five studies presented at ESTRO (European Society for Radiotherapy and Oncology) 2025 showcased how radiotherapy is reshaping the landscape for anal and rectal cancers. From reduced-dose treatments to cutting-edge combinations with immunotherapy and chemotherapy, these innovations offer safer, more effective, and organ-preserving alternatives to traditional surgery.
The PLATO-ACT4 trial, led by Professor David Sebag-Montefiore, MBBS, FRCR, FRCP, and colleagues, demonstrated that a reduced-dose, shorter-course highly focused radiotherapy technique (intensity-modulated radiation therapy [IMRT]) offers excellent tumor control with fewer side effects for early-stage anal cancer. The randomized phase II trial, conducted across 28 UK sites, showed similar efficacy and late toxicity levels using a reduced-dose IMRT regimen over 4.5 weeks and standard-dose IMRT over 5.5 weeks. “Our results support moving toward shorter, more personalized radiotherapy,” said Dr. Sebag-Montefiore. “This approach reduces the treatment burden for both patients and health-care systems.”
David Sebag-Montefiore, MBBS, FRCR, FRCP
Corrie Marijnen, MD
The STAR-TREC study showed that organ-preserving strategies are feasible for patients treated with radiotherapy alone as well as for patients treated with radiotherapy and chemotherapy. Among 344 patients at 37 international sites, 80% of those treated with chemoradiotherapy and 61% of those treated with radiotherapy alone could be spared surgery at 1 year. “Avoiding surgery helps preserve bowel function and quality of life,” said Professor Corrie Marijnen, MD, of the Netherlands Cancer Institute.
PRIME-RT, a trial conducted across the UK, found that 67% of evaluable patients receiving a short course of radiotherapy—meaning only five outpatient sessions (no overnight stay)—combined with immunotherapy had a complete response. “By combining immunotherapy with radiotherapy, we are seeing higher response rates than expected, especially with short-course radiotherapy,” said Professor Campbell Roxburgh, PhD, MBChB, of the University of Glasgow.
Similarly, in the STELLAR II trial from China, immunotherapy added to short-course radiotherapy and chemotherapy increased complete disappearance of the tumor for 45.5%, compared with 25% who had standard treatment. “By combining immunotherapy with short-course radiotherapy and chemotherapy, we may be able to improve survival rates and, crucially, help more patients avoid invasive surgery and its long-term effects,” said Professor Jing Jin, PhD, of the National Cancer Centre, China.
The phase III STELLAR trial tracked 591 patients in China with locally advanced rectal cancer over 5 years. It found that short-course radiotherapy followed by chemotherapy improved survival by 8.4% compared with standard long-course chemoradiotherapy—with no negative impact on anorectal function or quality of life. “This could be a game-changer for patients, offering a faster, equally safe, and potentially more effective option,” said Dr. Jin.
DISCLOSURE: For disclosures of all study authors, visit ESTRO.org.
