Female colon cancer patients who are 50 or younger have much better odds of surviving the disease than their male peers, but the opposite is true of older women with the disease, Australian researchers report.
"The age of 50 years is a surrogate for menopause, and the protective effects of estrogen on colorectal cancer may be the explanation," Dr Jenn H. Koo of Sydney South West Area Health Service and her colleagues suggest.
No study to date has looked specifically at the relationship between gender and colorectal cancer outcomes over time in patients newly diagnosed with the disease. To investigate, Koo and colleagues analysed data on 2,050 people diagnosed with colorectal cancer between 1997 and 2004. Forty-four percent were female.
They found that women aged 50 and younger were about half as likely to die from colorectal cancer as their male peers, no matter how advanced their disease was when it was diagnosed.
But older women were 38 percent more likely to die of the disease than men, again, independent of the stage of their tumour or whether or not it had spread.
A "limitation" of the study, the researchers note, is that it did not include information on whether women took hormones or when they actually went through menopause. Nevertheless, they say their finding is "important as it adds to the growing evidence that estrogen protects against colorectal cancer."
The researchers also note that because women were more likely to have proximal tumours (ie, those closer to the point where the colon joins the small intestine), flexible sigmoidoscopy - a colon cancer screening test that only examines the lower portion of the colon - may be less effective in female patients than colonoscopy, in which the entire large intestine is viewed.
"Our study revealed that 44 percent of women older than 50 years would not have been diagnosed with colorectal cancer if investigated with flexible sigmoidoscopy," they point out.