ESTRO 2024 Congress Report

Professor Marta Scorsetti, in her presentation at ESTRO 2024, explored the use of stereotactic body radiation therapy (SBRT) in the treatment of oligometastatic colorectal cancer (CRC). CRC is globally prevalent, and 60% of patients develop metastases within five years. About 20% of these cases are oligometastatic, characterised by a limited number of metastases and a more indolent disease that is suitable for local ablative treatments. Use of SBRT can increase local control to prevent symptoms, maintain quality of life, ablate visible metastases to prolong progression-free survival, reduce tumour burden to extend overall survival, ablate resistant clones to enhance systemic therapy efficacy, delay disease progression, and synergise with systemic therapies to improve outcomes.

Studies show that combining local treatment with systemic therapies improves the survival rates of those with oligometastatic CRC. Phase II trials demonstrate that aggressive approaches, such as a combination of radiofrequency ablation or resection with chemotherapy, significantly improve outcomes. SBRT has proven effective in controlling the disease with low rates of morbidity and toxicity. Clinical evidence shows that its use leads to high local control rates that are comparable with surgical outcomes for liver and lung metastases. Advantages of SBRT include its non-invasive nature, low toxicity, the feasibility of its use for most patients and body sites, the ability to use it to treat multiple lesions simultaneously, and its compatibility with most systemic therapies.

SBRT's effectiveness is highlighted in clinical scenarios such as the treatment of liver, lung and lymph node oligometastases. Key predictive factors for SBRT efficacy include radiation dose, tumour size, histotype and the success of previous treatments. Higher doses are correlated with better local control and overall survival rates, while smaller tumour volumes show better prognoses. Studies indicate that there are significant predictors of outcome, including the time from metastasis to the application of SBRT, the site of treated metastases, whether systemic therapy has been administered before SBRT, and control of treated metastases. For example, a study of 270 patients with 437 metastases found that a time from metastasis to SBRT treatment of more than 12 months, the site of the treated metastases, prior systemic therapy, and control of treated metastases were significant predictors of overall survival.

Prof Scorsetti concluded that future research should focus on phase III randomised controlled trials, the identification of true oligometastatic patients through the use of biomarkers and advanced imaging, and the exploration of interactions between local and modern systemic treatments. Ongoing trials, which are expected to conclude in the next few years, will help to refine treatment protocols and improve patient outcomes.

Prof Ciro Franzese

Humanitas University &Humanitas Research Hospital IRCCS, Rozzano, Milano, Italy