Radiotherapy for metastatic nodal disease in colorectal cancer

Radiation therapy (RT) is one of the main pillars of cancer treatment, using high-energy radiation to destroy or damage cancer cells by inducing DNA damage. Innovations in radiation techniques have enabled an evolving paradigm where ablative radiotherapy has become an acceptable treatment option to select cancer patients with limited disease. We review the available literature pertaining to RT in the setting of the oligometastatic state, oligometastatic colorectal cancer (CRC), and nodal CRC oligometastases. Key take aways are provided, including: 1) use of modern ablative radiotherapy techniques is safe and effective for nodal irradiation in the abdominopelvic cavity where unique dosimetric challenges of critical organs had previously limited dose escalation; 2) dose escalation is imperative to optimize local control and may contribute to a benefit in overall survival; 3) RT can be integrated into the treatment strategy of incorporating repeated use of local treatments for limited-extent relapse and prolonged chemotherapy-free survival; and, 4) selection for certain prognostic factors can define patient subgroups who derive greatest benefit from RT. We further suggest practical considerations in patient selection and details on treatment planning/delivery based on curations of the literature’s reported experience and our institutional practice; case examples are also reviewed. As much of the evidence pertaining to treatment of nodal CRC oligometastases is limited to retrospective and/or heterogeneous patient cohorts, prospectively enrolled trails are needed to confirm safety and efficacy, as well as better define dose constraints and optimized dose regimens. Particle therapy, image-guided adaptive RT, and biology-guided RT techniques have promising applications in the treatment of oligometastatic CRC.