Nephrotic syndrome may raise the risk of cancer by > 70%—and has a “noteworthy” association with certain cancers—according to researchers from Aarhus University Hospital, in Denmark, Dartmouth Medical School, in Hanover, New Hampshire, and University of North Carolina, Chapel Hill.
Case reports and case series have long suggested that nephrotic syndrome and occult cancer are linked, the researchers say. For instance, one study found a more than double cancer risk during the 15 years after diagnosis with membranous nephropathy. In that study, as many as 21% of patients were diagnosed with cancer during a median follow-up of 6.2 years. The high risk might be explained by the focus on membranous nephropathy, a condition known to be associated with cancer, the researchers say. But the studies were very small and lacked comparison groups. Moreover, there have been no formal epidemiologic studies in a population-based setting.
In this study, the researchers analyzed data from about 7.8 million people in the Danish National Registry of Patients, estimating the 5-year risk of incident cancer in the 4,293 patients with nephrotic syndrome. The researchers found a 4.7% 5-year risk of any cancer, with the highest risk for lung cancer, multiple myeloma, and prostate cancer. Over the entire follow-up period, 196 cancers were “expected,” but 338 cancers were observed. The elevated risk was highest during the first 6 months after nephrotic syndrome was diagnosed, but remained elevated through the long-term follow-up.
Five-year mortality rates were 68.5% for patients with nephrotic syndrome, compared with 63.4% in patients without nephrotic syndrome. At 1 year, mortality was 40.8% (95% confidence interval [CI], 35.7-46.4) in patients with nephrotic syndrome, and 38.4% (95% CI, 36.0-40.8) in those without. The impact of nephrotic syndrome on 1-year mortality was most pronounced in patients with hematologic malignancy. After adjusting for age, gender, and comorbidity, the researchers found a hazard ratio of 1.2 for mortality in patients with cancer following nephrotic syndrome, with the most pronounced effect in those with localized cancer.
Despite a low absolute risk of most cancers, the researchers conclude, their findings suggest that clinical workups might logically focus on lung cancer and multiple myeloma when there is a suspicion of co-occurring signs or symptoms in patients with nephrotic syndrome.
Source
Christiansen CF, Onega T, Sværke C, et al. Am J Med. 2014;127(9):871-877.
doi: 10.1016/j.amjmed.2014.05.002.
