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Second cancer after female breast cancer
Improvements in diagnosis and treatment for
breast cancer have led to an increase in the number of women who are
long-term survivors after a diagnosis of breast cancer. Previous studies
have shown that breast cancer survivors are at increased risk for
developing a new primary cancer. With the inclusion of 525,527 women with
breast cancer, the present study is much larger than the previous ones, so
we were able to estimate the risk for second cancer after breast cancer
with much greater precision. The women with breast cancer were identified
in 13 Cancer Registries in Europe, Canada, Australia and Singapore and
followed for a second primary cancer within the period 1943-2000. The
incidence of a new primary cancer was compared with incidence rates for
first primary cancer. We found an increased risk of 1.25 for all
second cancer sites combined (not including contralateral breast). The
overall increase was due to excesses of many different types of cancer
such as cancer of the esophagus, stomach, colorectum, lung, non-melanoma
skin, endometrium, ovary, bladder, kidney, thyroid gland as well as soft
tissue sarcoma, melanoma and leukaemia and several other types. A
decreased risk was seen for a few cancer sites including liver, cervix,
brain and nervous system and multiple myeloma. We had no information on the type of breast cancer treatment that the women had received, but analyses of risk by time since breast cancer diagnosis and analyses of risk of second primary breast cancer after a first primary non-breast cancer of various types gave indications of whether the observed associations could be caused by treatment or shared risk factors. The excess of cancer at many different sites suggests that there may be additional explanations such as increased surveillance and general cancer susceptibility.
Bibliographical reference: Lene Mellemkjær et al.: "Risk of second cancer among women with breast cancer", Int J Cancer. 2005 Dec 8; [Epub ahead of print]
Lene Mellemkjær Institute
of Cancer Epidemiology, Danish Cancer Society, Copenhagen, Denmark
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