A hysterectomy done for indications other than cancer may increase a woman's risk for renal cell carcinoma, a large Swedish study shows.
The researchers emphasise that the increase in risk is very small, but even so, said lead researcher Dr Daniel Altman of the Karolinska Institutet in Stockholm, "We're looking at a potentially preventable cause."
Retrospective studies had already shown a link between renal cell carcinoma and hysterectomy, but in the new study Dr Altman and his colleagues used a more rigorous method. They followed more than 800,000 women with and without hysterectomies over 30 years to see who developed this uncommon cancer.
There were about 17 yearly cancer cases per 100,000 women who'd had had their uterus removed compared to 13 among those who still had it, the researchers reported in the Archives of Internal Medicine.
After adjustment for potential confounding variables -including the year the hysterectomy was performed, the woman's county of residence and whether or not she had given birth, women without a uterus were 50% more likely to develop renal cell cancers.
Double the kidney cancer risk
Further, women who had the procedure before the age of 44 -a growing number, according to the researchers, appeared to be hardest hit, with more than double the chances of kidney cancer compared to those who still had their uterus.
The risk for these younger women was highest within the first 10 years after surgery and then declined over time.
Bladder cancer risk
While the link was weaker, the same patterns held true for the risk of bladder cancer.
The researchers can't explain their findings. Dr Altman's first guess was that underlying medical conditions were behind the effect rather than the hysterectomy itself. But when he and his team tested that theory, they came up empty.
"We're left to speculating," he said. "Perhaps when you remove the organ, you alter the architecture and change the support and flow from the kidney to the bladder. But we're not sure."
Dr Altman stressed that the findings do not suggest that women shouldn't have hysterectomies. "If you look at the millions of the procedures performed across the industrialised world each year, then the (additional risk) may be significant," he said. "But for an individual, the risk is quite low."
Still, he notes there are often other treatment options the non-cancer conditions that lead many women to seek a hysterectomy.
(Reuters Health, Lynne Peeples, December 2010)