Risk for Colorectal Cancers
Although it may not seem it at first glance, this is actually good news. A recent article in the American Journal of Gastoenterology found that women previously diagnosed with breast cancer do not have a higher risk of developing any kind of colorectal cancers than the general population. Since there had previously been some concern about this possibility, and because many of us feel especially vulnerable, this is reassuring news.
Breast cancer survivors at same risk for CRC as general population
By Catherine Nieman Sims
27 May 2009
Am J Gastroenterol 2009; 104: 1213-1220
MedWire News: Women diagnosed with breast cancer do not have an increased risk for right-sided colorectal cancer (CRC) or CRC in general, a Canadian study shows.
It has been suggested that estrogen may affect the development of right-sided CRC (cancer of the cecum, ascending colon, and hepatic flexure), and indeed some studies have shown an increased risk for CRC following breast cancer. However, results are conflicting.
Harminder Singh (University of Manitoba, Canada) and colleagues determined the incidence of right-sided CRC after the diagnosis of breast cancer in this large, population-based study, which is published in the American Journal of Gastroenterology.
The Manitoba Cancer Registry was used to identify all women diagnosed with breast cancer in Manitoba between 1956 and 2006. A total of 23,377 women were followed-up for a median of 6.3 years, with a cumulative follow-up duration of 221,364 patient-years.
There were 412 cases of CRC diagnosed in the study population, of which 145 were right-sided CRC. The median age at diagnosis of these 412 cases was 76 years, which was not significantly different from the average age of CRC diagnosis in the general population (72 years).
The standardized incidence ratios (SIRs) showed that a prior diagnosis of breast cancer did not increase the risk either for all CRC (SIR=0.96) or for right-sided CRC (SIR=1.02).
There was also no increased risk when results were stratified according to age at diagnosis or period of diagnosis (1956-1984 vs 1985-2006). Tamoxifen use did not affect the incidence either (all CRC, SIR=1.22; right sided CRC, SIR=0.90).
The results clearly show that a diagnosis of breast cancer - which the authors hypothesized might predispose to increased estrogen activity and thereby a higher risk for right-sided CRC - does not affect the risk for any type of CRC.
Singh et al therefore recommend that the "screening strategy for breast cancer survivors should be similar to that for the general population.