More than one in four smokers undergoing kidney cancer surgery had advanced stages of the disease, compared to only one in five patients who didn't light up.
Researchers say about 70 per cent of people with early-stage tumours survive at least five years, whereas that number plummets to just eight per cent after the cancer has begun spreading.
About one in 70 Americans, most of them elderly, develop kidney cancer, according to the American Cancer Society.
But the findings aren't all bad news. Indeed, former smokers who'd kicked the habit had a smaller chance of turning up with advanced cancer.
While the study wasn't designed to prove that quitting can slow tumour growth, Dr. Thomas J. Polascik, who led the work, said he believes that to be the case.
"It can't bring you down to the risk of a nonsmoker, but it can get you almost there," Polascik, a surgeon at Duke University in Durham, North Carolina, told Reuters Health. His findings appear in the Journal of Clinical Oncology.