Social isolation: Impact on treatment and survival in patients with advanced cancer.

156 Background: Social relationships are an important determinant of health, with impacts on morbidity and mortality in the general population. The influence of social isolation in patients with metastatic cancer is less clear, as are the potential mechanisms of its effect. We sought to examine patient-reported social support in a large unselected population, and explore the impact on outcome. Methods: A retrospective review was completed of all patients with metastatic cancer referred to BC Cancer from 2011-2016 who completed a psychological screen within six months of diagnosis. Social isolation was defined as a positive response to any of five questions about social support: live alone, recently lost spouse/partner, no regular contact with friends/relatives, no one to assist with IADLs, no emotional support. An isolation score was calculated as the number of positive responses. The primary outcome was overall survival (OS). Results: 7,699 patients were included in the study. Baseline characteristics: median age 68, 57% male, 60% received systemic therapy, primary tumor site 4% breast / 37% lung / 28% GI / 13% GU / 18% other. 5191 (67%) patients reported no isolation, and 2,538 (33%) were socially isolated. Patients with social isolation were more likely older (median age 70 vs. 67), female (50% vs. 40%), ECOG ≥2 (34% vs. 30%), and receive no systemic therapy (46% vs. 35%). Median OS was inferior in socially isolated patients at 10.1 m compared to those with no isolation at 13.5 m (p<0.001). In a multivariate model including age, sex, ECOG, systemic therapy, and primary tumor site, the impact of social isolation on OS remained significant (HR 1.06, p=0.04). In an exploratory analysis, increasing levels of social isolation were correlated with reduced systemic therapy uptake (score 0=65% received systemic therapy, 1=56%, 2=53%, 3=47%, ≥4=43%, p<0.001). Conclusions: Socially isolated patients with metastatic cancer have inferior survival, which may be influenced by the reduced use of systemic therapy. Increasing patient social support should be explored as a means to improve the uptake of systemic therapy and its benefits on survival in patients with advanced cancer.