Clinical application of stereotactic body radiation therapy for colorectal cancer with liver metastases

Objective: To evaluate the efficacy of stereotactic body radiation therapy (SBRT) for hepatic metastases from colorectal cancer, and to collect data for the application of this technique. Methods: A total of 28 patients from No.306 Hospital of PLA, including 17 male and 11 female with median age of 63.8 (range from 31 to 86), were treated with SBRT for colorectal cancer with liver metastases with 54 lesions in total. The GTV, CTV and PTV were delineated above the enhanced CT scans acquired during normal quiet respiration. CTV was obtained by adding 5 mm isotropic margin from GTV, and PTV was obtained by adding 5 to 10 mm isotropic margin from CTV. Prescription dose line covered 50%-60% of isodose curve at 3-6 Gy/fraction. The total dose was 39-45 Gy and the biologically equivalent doses(BED) was 50.7-65.3 Gy. The patients were followed-up beginning at 3 months after SBRT. The change in size of the lesion based on enhanced CT or MR scans was evaluated. Toxicity was evaluated and scored according to the RTOG criteria. Local control rate and survival rate were analysed. Results: All patients completed the treatment. With median follow-up of 15.1 months (range frome 3 to 30 months), 7 patients survived at the end of follow-up. The local control rate (LC) was 79.2%, and 1- and 2-year overall survival rate(OS) were 82.7% and 48.6%, respectively. There was a close corelation between the size of lesion and the LC. The LC(PR + CR) was much better at the size of lesion less than 14 cm³ than that at the size more than 65 cm³(χ² = 4.17, P < 0.05). When the size was more than 180 cm³, the LC was zero. Toxicity included fatigue(60.7%), grade 1 and 2 digestive system toxicity(28.6%), a transient grade 1 and 2 bone marrow suppression(46.4%) and a transient increase in transaminase(17.8%). No grade 3 toxicity and above and late toxicity were observed. Conclusions: Stereotactic body radiation therapy could be suggested as the first choice for the selected patients who suffer form colorectal liver metastases, especially for those who cannot undergo surgery. (authors)