Metastasectomy is hypothesised to improve overall survival (OS) in patients with metachronous metastasis of STS. Evidence in favour of this approach comes from non-controlled single-arm studies subjected to selection bias. In the present study, advanced comparative effectiveness methods were used to assess the efficacy of metastasectomy vs. “non-invasive” treatments (i.e. chemotherapy, radiotherapy, best supportive care) in patients with metachronous STS-metastasis.
135 patients with metachronous STS metastasis, selected out of a population of over 1000 STS patients, who had primarily undergone surgery for localised STS between 1998 and 2015 at two tertiary tumour centres were retrospectively included. In order to evaluate the efficacy of metastasectomy on OS, a propensity score (PS) was estimated, including variables at time of treatment decision for metastatic disease (“baseline”). Based on the PS, an inverse-probability-of-treatment-weight (IPTW) model was calculated to allow analyses with adjustment for favourable prognostic factors prevailing in patients undergoing metastasectomy (for metastasectomy: IPTW=1/PS; for “non-invasive” treatment: IPTW=1/(1-PS)).
OS was significantly better in those 68 patients (44.4%) who had undergone metastasectomy (10-year OS: 23% vs. 4%; log-rank test: p < 0.0001; hazard ratio (HR): 0.34, 95% confidence interval (CI): 0.22-0.53, p < 0.0001). This positive association prevailed after recalculation of time-to-event-analyses with IPTW-weighted data ((adjusted 10-year OS: 17% vs. 3%, log-rank-test: p < 0.0001; HR: 0.33, 95%CI: 0.20-0.52, p < 0.0001), compensating for positive prognostic factors prevailing in patients with metastasectomy (i.e. smaller number of metastases, better ECOG performance status, better haemoglobin- and albumin-levels).
In the present bi-centre study, metastasectomy was associated with a significant benefit on OS, persisting even after adjustment for favourable prognostic factors prevailing in patients undergoing metastasectomy. Our data indicate that metastasectomy should be considered as first choice in patients with metachronous metastasis of STS.
Clinical trial identification
Legal entity responsible for the study
Medical University of Graz.
Has not received any funding.
All authors have declared no conflicts of interest.