In fact for some cancers, being married might be a more potent factor for cancer survival than chemotherapy, the study found.
Lead study author Dr. Ayal Aizer, a chief resident in radiation oncology at Harvard Medical School in Boston, said married patients were also more likely to be diagnosed with earlier-stage disease and much more likely to receive the appropriate therapy.
The study was the first to show a consistent and significant benefit of marriage on survival among each of the 10 leading causes of cancer-related death in the United States -- lung, colorectal, breast, pancreatic, prostate, liver/bile duct, non-Hodgkin lymphoma, head and neck, ovarian and esophageal cancer, Aizer said.
For patients with prostate, breast, colorectal, esophageal and head and neck cancers, marriage was associated with a survival increase that was larger than that of standard chemotherapy regimens for those diseases.
The study assessed clinical and demographic data from the National Cancer Institute's SEER database on 734,889 patients diagnosed from 2004-08.
The analysis, published in The Journal of Clinical Oncology, showed, overall, patients who were married were 17 percent less likely to have metastatic disease when first diagnosed with cancer compared with patients who were not married.
In addition, married patients with non-metastatic disease were 53 percent more likely to receive therapy indicated for their disease compared with unmarried patients and at any given time. Finally, at any given time, a patient who was married was 20 percent more likely to be alive than a patient who was not married, the study said.
"Marriage probably improves outcomes among patients with cancer through increased social support," Aizer said in a statement.
"Our results suggest that patients who are not married should reach out to friends, cancer support or faith-based groups, and their doctors to obtain adequate social support."