Assessment of Modifiable Factors for the Association of Marital Status With Cancer-Specific Survival

Abstract

Married patients with cancer have better cancer-specific survival than unmarried patients. Increasing the early diagnosis and definitive treatment of cancer among unmarried patients may reduce the survival gap. To evaluate the extent to which marriage is associated with cancer-specific survival, stage at diagnosis, and treatment among patients with 9 common solid cancers and to recommend methods for reducing the survival gap. This retrospective, population-based cohort study included patients older than 18 years who were diagnosed with 1 of 9 common cancers between January 1, 2007, and December 31, 2016. Patient data were retrieved from the Surveillance, Epidemiology, and End Results Program. Statistical analyses were performed from August 1 to October 1, 2020. Marital status, classified as married and unmarried (including single, separated, divorced, widowed, and unmarried patients or domestic partners). The primary outcome was the time ratio (TR) of cancer-specific survival (married vs unmarried). Mediation analyses were conducted to determine the extent to which the association of marriage with cancer-specific survival was mediated by stage at diagnosis and treatment. This study included 1 733 906 patients (894 379 [51.6%] women; 1 067 726 [61.6%] married; mean [SD] age, 63.76 [12.60] years). Multivariate analyses found that those who were married were associated with better cancer-specific survival than unmarried patients (TR, 1.36; 95% CI, 1.35-1.37). Early diagnosis in breast cancer, colorectal cancer, endometrial cancer, and melanoma mediated the association between marital status and cancer-specific survival (breast cancer: proportion mediated [PM], 11.4%; 95% CI, 11.2%-11.6%; colorectal cancer: PM, 10.9%; 95% CI, 10.7%-11.2%; endometrial cancer: PM, 12.9%; 95% CI, 12.5%-13.3%; melanoma: PM, 12.0%; 95% CI, 11.7-12.4%). Surgery mediated the association between marital status and cancer-specific survival in lung (PM, 52.2%; 95% CI, 51.9%-52.4%), pancreatic (PM, 28.9%; 95% CI, 28.6%-29.3%), and prostate (PM, 39.3%; 95% CI, 39.0%-39.6%) cancers. Chemotherapy mediated the association of marital status with cancer-specific survival in lung (PM, 37.7%; 95% CI, 37.6%-37.9%) and pancreatic (PM, 28.6%; 95% CI, 28.4%-28.9%) cancers. Improved cancer-specific survival associated with marriage was greater among men than women (men: TR, 1.27; 95% CI, 1.25-1.28; women: TR, 1.20; 95% CI, 1.19-1.21). The contribution of receiving an early diagnosis and treatment with surgery or chemotherapy to the association between marital status and cancer-specific survival was greater among men than women (early diagnosis: PM, 21.7% [95% CI, 21.5%-21.9%] vs PM, 20.3% [95% CI, 20.2%-20.4%]; surgery: PM, 26.6% [95% CI, 26.4%-26.7%] vs PM, 11.1% [95% CI, 11.0%-11.2%]; chemotherapy: PM, 6.8% [95% CI, 6.7%-6.8%] vs PM, 5.1% [95% CI, 5.0%-5.2%]). In this study, survival disparities associated with marital status were attributable to early diagnosis in breast, colorectal, and endometrial cancers as well as melanoma and to treatment-related variables in lung, pancreatic, and prostate cancers. The findings also suggest that marriage may play a greater protective role in the cancer-specific survival of men than of women.