Survival Of Patients With Oligometastases Treated With Palliative Intent

Patients considered to have oligometastases (OM), either de novo or induced, have been increasingly approached with ablative intent. However, what exactly comprises OM has been inconsistently described, making interpretation of published data challenging and the exact prevalence unknown. A 2019 international consensus statement proposed a definition of a maximum of five metastases (M) involving three sites. We examined survival relative to metastatic burden in a population historically treated with palliative-intent radiotherapy (PRT) and/or best supportive care. Consecutive patients referred to our tertiary cancer center’s Palliative Radiation Oncology and/or Palliative Care programs were entered in an IRB-approved prospectively maintained database within a larger study of survival prediction, with collection of patient, disease and treatment data (06/2010-12/2014). Number and site(s) of M at first clinic visit during this period were retrospectively collected. Summary statistics were obtained. Kaplan Meier (KM) survival estimates reported medians and 95% confidence intervals (CI). Log-rank statistics compared KM curves. For our 980 patients, median age was 65.1 years (range 18.9-91.9 yrs); 58.2% were male; 36.2% had a lung and 28.2% a genitourinary primary; 65.3% received PRT. Karnofsky Performance Status was available in 611 patients and was ≥70 in 50.6%. Overall median survival (MS) was 4.1 months (95%CI 3.7-4.5m). The median number of M was 8 (range 1-105). 9608 metastases were clinically and/or radiologically identified, most commonly bone (66.9% of patients; 4912 M), lung (34.2%; 899 M) and brain (29.0%; 884 M). 58 had ‘innumerable’ lesions. The median number of sites involved was 2 (range 1-10). 255/980 (26.0%) had 1-5 M and 660/980 (67.3%) had 1-3 sites. MS for patients with 1-5 M affecting 1-3 sites was 5.9m (95%CI 4.6-7.2m). However, 38/247 who would otherwise have met the consensus definition for OM had involvement of an exclusionary site, most commonly a pleural effusion, resulting in 209 patients with OM as per the International Consensus definition. MS significantly differed between those who met vs did not meet the consensus definition: 6.6m (95%CI 5.1-8.1m) vs 3.6m (95%CI 3.2-4.0m), p<0.0001. Within a historic cohort approached with palliative intent, omitting those with involvement of an exclusionary site, MS of those meeting the 2019 International Consensus definition for OM was 6.6 months.