Session Item

Operability status is prognostic for survival after SABR in primary non-small cell lung cancer. Subtotal ablation of all sites of oligometastases was negatively predictive of progression free survival (PFS) in the ORIOLE phase II trial. This study aims to assess the prognostic influence of operability and total metastatic ablation of all sites of oligometastatic disease.

Consecutive patients had operability status and presence of subtotal versus total metastatic ablation recorded prospectively on an institutional database. Data was retrospectively analysed with institutional ethical approval. Inclusion criteria was 1-5 sites of active extracranial oligometastases. The primary objective was to compare overall survival (OS) and PFS between cohorts. Secondary objectives were to describe patterns of failure, high grade treatment toxicity (CTCAE v4.0), and freedom from systemic therapy (FFST). Multivariable Cox regression was performed to adjust for age, ECOG, Charlson Comorbidity Index (CCI), synchronous vs. metachronous oligometastases and number of metastasis at time of SABR.

401 patients with 530 treated oligometastases were included, with a median follow-up of 3 years. The median age was 67 years and 67% were male. Common histologies included prostate (24%), lung (18%), gastrointestinal (19%) and breast (11%). The total number of metastases (currently active and prior) was 1 in 47% of patients, 2-5 in 51%, and >5 in 2%. Radical treatment to the primary was delivered in 96% of patients. Grade 3-4 toxicities were reported in 3% (n=14). Cumulative incidence at 5-years of local only failure was 6%, local and distant was 2%, and distant only failure was 58%. The 3- and 5-year OS [95% CIs] were 68% [62-73] and 54% [47-61], and PFS was 20% [15-25] and 14% [10-20]. The 3- and 5-year FFST [95% CIs] was 40% [34-46] and 31% [24-37]. 76 patients were medically inoperable and 325 were medically operable. Inoperable patients were older (median 73 vs 65 years), had a higher CCI (median 10 vs 8) and poorer ECOG status (47% ECOG 0 vs 71%) than operable patients (all p-values <0.001). Operability status was not prognostic for OS (logrank p=0.095) or for PFS (logrank p=0.9), (Figure 1). The adjusted HR was 1.0 (95% CI: 0.6-1.7; p=0.9) for OS and 1.1 (95% CI: 0.8-1.6; p=0.5) for PFS. Total metastatic ablation was prognostic for OS (logrank p=0.011) and for PFS (logrank p=0.001), (Figure 2). The adjusted HR for OS was 0.8 (95% CI: 0.4-0.9; p=0.032) and for PFS was HR 0.6 (95% CI: 0.4-0.8; p=0.003).

Medical operability is not independently prognostic in our cohort with oligometastatic disease. Total metastatic ablation is associated with an improved OS and PFS compared with subtotal metastatic ablation. This data suggests that treatment of all sites of metastases  should be optimised.