Verhoogde
kans op nieuwe kanker na borstkanker.*
Uit
een studie onder ruim 525.000 patiënten met borstkanker in Europa, Canada, en
Australië blijkt dat vrouwen die borstkanker gehad hebben 25% meer kans hebben
een andere kankersoort te krijgen. De studie omvatte de periode van 1943 tot 2000 en ruim 133.000 vrouwen werden tien jaar
lang gevolgd nadat ze borstkanker gekregen hadden. Deze resultaten zijn deels te
verklaren door bepaalde leefomstandigheden maar ook door gebruikte therapieën
zoals bestraling en chemo.
Women
With Breast Cancer Face Increased Risk Of Developing A Second Cancer
A
new large-scale study on women with breast cancer
found a 25 percent increase in the risk of developing a new non-breast cancer
compared to women without cancer. The study,
published online December 8, 2005 in the International Journal of Cancer, the
official journal of the International Union Against Cancer (UICC), is available
via Wiley InterScience (http://www.interscience.wiley.com/journal/ijc).
Breast
cancer is the most common cancer among women in developed countries. Due to the
high five-year survival rate (77 percent), a considerable number of women have a
long-term risk of developing a second cancer. Previous studies have shown a
20-30 percent increased risk for a second cancer in various sites, including the
endometrium, ovary, thyroid, lung, soft tissue,
blood, skin, stomach and colon, with higher risks
among younger patients.
Researchers
led by Lene Mellemkjær of the Danish Cancer Society in Copenhagen, Denmark
conducted a huge study involving 525,527 patients
with breast cancer in 13 cancer registries in Europe, Canada, Australia and
Singapore. Records were analyzed for second primary cancers during the period
1943 to 2000, with 133,414 women followed for more than 10 years after the
initial diagnosis of breast cancer. The increased risk of a second cancer was
seen in many different sites, as shown in earlier studies. "The excess of
cancer after a breast cancer diagnosis is likely to be explained by treatment
for breast cancer and by shared genetic or
environmental risk factors although the general excess of cancer suggests that
there may be additional explanations such as increased surveillance and general
cancer susceptibility," the authors note.
The
study found an almost 6-fold increase in the risk of cancer in connective tissue
of the thorax and upper limbs, which suggests that radiation therapy, which has
been used to treat breast cancer since the beginning of the 20th century, may
play a role in developing a second cancer in organs close to the breast. An
increased risk of myeloid leukemia was also shown, possibly as a result of
chemotherapy. In addition, while previous studies had shown an increased risk of
endometrial cancer with the use of tamoxifen, the current study suggests that
this may not be entirely due to the drug, since the increased risk was already
shown within one year of breast cancer diagnosis, it was shown before 1975 when
tamoxifen was rarely used, and an increased risk of breast cancer was also seen
after endometrial cancer. Colorectal, kidney and postmenopausal breast cancer
appear to share obesity as a risk factor, while ovarian cancer and breast cancer
seem to have a genetic predisposition in common. The study found an excess of
ovarian cancer already within one year of breast cancer diagnosis, along with an
increased risk of breast cancer after ovarian cancer.
"The overall impression from this very large study is that a breast cancer diagnosis has an effect on subsequent cancer risk in general, since so many cancer sites were seen to occur in excess of what was expected," the authors conclude. "The known effects of treatment and common risk factors do not seem to fully explain the excesses." (December 2005) (Opm. Kijk bij Specifiek advies voor adviezen ter voorkoning van kanker.)
