Superior outcomes of nodal metastases compared to visceral sites in oligometastatic colorectal cancer treated with stereotactic ablative radiotherapy
Séan M. O’Cathail, Thomas J. Smith, Rob Owens, Anthi Zeniou, Y. Tsang, D. Holyoake, Louise Murray, Mark Harrison, M. Hawkins
Abstract
BACKGROUND: Stereotactic ablative radiotherapy (SBRT) is a radical option for oligometastatic colorectal cancer (CRC) patients, but most data relate to visceral metastases. METHODS: A prospective, multi-centre database of CRC patients treated with SBRT was interrogated. Inclusion criteria were ECOG PS 0-2, ≤3 sites of disease, a disease free interval of >6 months unless synchronous liver metastases. Primary endpoints were local control (LC), progression free survival (PFS) and overall survival (OS). RESULTS: 163 patients (172 metastases) were analysed. The median FU was 16 months (IQR 12.2-22.85). The LC at 1 year was 83.8% (CI 76.4%-91.9%) with a PFS of 55% (CI 47%-64.7%) respectively. LC at 1 year was 90% (CI 83%-99%) for nodal metastases (NM), 75% (63%-90%) for visceral metastases (VM). NM had improved median PFS (9 vs 19 months) [HR 0.6, CI 0.38-0.94, p = 0.032] and median OS (32 months vs not reached) [HR 0.28, CI 0.18-0.7, p = 0.0062] than VM, regardless of whether the NM were located inside or outside the pelvis. On multivariate analysis, NM and ECOG PS 0 were significant good prognostic factors. An exploratory analysis suggests KRAS WT is also a good prognostic factor. CONCLUSION: Nodal site is an important prognostic determinant of SBRT that should incorporated into patient selection. We hypothesise this may have an immunoediting basis.