Case Report: Innovative radiotherapy strategies in advanced colon cancer with oligometastasis: a case of online adaptive radiotherapy and lattice stereotactic re-irradiation

Conventional radiotherapy demonstrates limited efficacy in advanced colon cancer with bulky radio-resistant metastatic lesions. A case report detailing the outcomes and toxicity profile of a 71-year-old female with progressive colon cancer and pulmonary oligometastasis treated using an individualized radiotherapy approach is presented. The patient, with an ECOG performance status of 3, presented severe symptoms including partial intestinal obstruction, intractable cough, and hemoptysis following multiple lines of systemic therapy and prior intensity-modulated radiotherapy (IMRT) to lung metastases (5750 cGy in 23 fractions, delivered 17months earlier). Following multidisciplinary evaluation, online adaptive radiotherapy (oART) using a fan-beam CT-guided linear accelerator system was administered to the ascending colon primary tumor (50 Gy in 25 fractions). Concurrently, spatially fractionated radiotherapy (SFRT) was employed for the radio-resistant bulky pulmonary lesion: lattice radiation therapy (LRT) PTVpeak (22.5 Gy in 3 fractions) followed by sequential conventional fractionation to PTV (30 Gy in 15 fractions). No acute radiotherapy-related adverse events were observed. At 11-month follow-up, both target lesions exhibited partial response (PR) on imaging, accompanied by complete alleviation of intestinal obstruction and hemoptysis. Consequently, the patient’s performance status improved to ECOG 1. oART appears to be a viable approach for symptom palliation and disease control in advanced colon cancer with emergent complications, particularly among patients with compromised functional status. Additionally, SFRT shows potential efficacy in re-irradiation settings for bulky, radio-resistant lesions. The combined use of adaptive precision radiotherapy and spatially fractionated techniques may therefore represent an emerging therapeutic paradigm for oligometastatic colon cancer, meriting further evaluation in prospective clinical trials.