Stereotactic Body Radiotherapy (SBRT) for Patients with Oligometastases From Colorectal Cancer (CRC): Interim Results of a Phase II Study

Abstract

To present the preliminary results of SBRT for oligometastases primary from colorectal cancer. This is a prospective, observational, single-arm phase II study. 49 patients with oligometastases from CRC were prospectively selected for SBRT between January 2016 and February 2019. Inclusion criteria are: histologically proven CRC, age ≥18 years old, controlled primary tumor, controlled extra-hepatic or extra-pulmonary lesions, ECOG performance status 0-1, at least one measurable lesion but less than 5, not a candidate for surgical resection. Patients who have liver metastasis undergo a percutaneous, Ultrasound-guided, fiducial marker implantations, then simulate with abdominal compression using 4-dimentional CT (4D-CT) and MRI. The gross tumor volume (GTV) is delineated in each 4D-CT phase, the internal target volume (ITV) was the envelope of GTVs from each phase of 4D-CT. The planning treatment volume (PTV) was ITV plus an isotropic margin of 3-5 mm. For patients of lung metastasis, 4D-CT simulation or simulation in DIBH are all allowed. The dose and fractionation are chosen according to the location and size of lesion. Cone-beam CT (CBCT) will be used to verify patient positioning at every treatment. The primary endpoint is 3-year local control rate (LC), secondary endpoint is ≥ G3 treatment-related toxicities and 3-year overall survival. We plan to enroll 50 patients until December 2020. All patients signed the informed consent, the study is approved by Ethics Committee. Forty-five patients (59 lesions) are amenable to analysis, including 32 males and 13 females. The median age is 62 years old (39-79). There are 35 hepatic lesions, 21 pulmonary lesions, and 3 lesions located in lymph nodes. The most common primary site is rectum (30 patients), while 12 patients have colon cancer, and 3 patients have bi-primary carcinoma. The median ITV is 12.612 cm3 (1.07-160.54 cm3). The median PTV is 31.726 cm3 (5.296- 323.117cm3). The median BED for lung metastasis is 100Gy (72Gy - 119Gy) and 96Gy (48-151.2 Gy) for hepatic metastasis. The median follow-up is 21 months for pulmonary lesions and 16 months for hepatic lesions. At the time of analysis, 13 lesions have local recurrence, 3 lesions are pulmonary, 1 lesion is of spleen, another 9 lesions are hepatic. One-year LC is 78.8%. 1-y pulmonary LC is 92.9%, and 68.7 % for hepatic lesion. Four patients died. The median OS is 10.5 months. One-year OS is 94.5%. Treatments were well-tolerated. For patients who have liver metastasis, no patient developed grade 3 radiation-induced liver disease. Some patients had transiently increased levels of hepatic transaminase, which normalized within 3 months after SBRT. Other side effects are nausea, anorexia, fatigue, gastritis. No patients had severe (grade 3-5) pulmonary toxicity. Some patients may have radiological change, but no clinical symptoms presented. SBRT is safe and effective for oligometastases from colorectal cancer under respiratory motion management and robust quality assurance.