Primary and secondary bilateral breast cancers share common features
MedWire News: US researchers have demonstrated that hormone receptor status, tumor grade, and histological type are strongly concordant between primary and secondary bilateral breast cancers.
This supports "the notion that two tumors arise in a common milieu and that tumor subtypes are predetermined in the early stage of breast carcinogenesis," write Dezheng Huo (University of Chicago, Illinois) and colleagues in the journal Cancer.
"Women with breast cancer are more likely to have a second breast cancer than women in the general population are to have a primary cancer," the researchers explain.
To gain a better understanding of the relationship between first and second breast cancers, the team studied 30,617 patients diagnosed with bilateral breast cancer between 1990 and 2007.
They specifically assessed the associations of tumor histological type, tumor grade, estrogen receptor (ER), and progesterone receptor (PR) status between first and second breast cancers. They also examined the factors that modify these associations.
The team reports that for patients in whom the first cancer was ER-positive, the chance that the second cancer was ER-positive was 87.5%, compared with 47.8% for patients in whom the first cancer was ER-negative.
The odds ratio (OR) for having two breast cancers with the same ER status was 7.64.
However, the strength of the association between estrogen receptor status depended on the time interval between the first and second tumors and age at diagnosis, note Huo et al.
Specifically, when the second tumor occurred within 1 month of the first (synchronus), the OR for having the same ER status was 25.9. This association reduced over time and levelled off at around 12 months. Even so, the OR was still 3.69 for metachronous tumors separated by 10 or more years.
The strength of association for ER status was also greater among patients whose first cancer was diagnosed before 50 years of age (OR=11.7) compared with those diagnosed after age 50 years (OR=5.71).
The relationships for PR status, tumor grade, and histological type in primary and secondary cancers were similar to those for ER status but with relatively weaker associations.
"These findings have important implications in the prevention and management of second breast cancers," say Huo and co-authors.
"For a specific individual with initial breast cancer, the risk factors for her second breast cancer may be the same as for the first one, thus a similar systemic management may be appropriate for the second cancer," they conclude.
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By Laura Dean