 |
Jan. 3, 2007 — Why don’t people
get heart cancer?
 |
Response
by Rick Lee
Visiting scientist |
|
The short answer is that people do get heart
cancer, but it’s a very rare disease. The incidence
in autopsy studies vary between 0.0017% and 0.28%. To
put that into perspective, the data from the US National
Cancer Institute’s Surveillance Epidemiology and
End Results (SEER) database from 2000-2002 indicate
that the lifetime risk of a male in the US developing
invasive cancer is 45.7%, with a 23.6% risk of dying
from cancer. For women, those risks are 38.1% and 19.9%,
respectively (For more information on cancer risk, visit
http://www.cancer.org/docroot/CRI/content/CRI_2_6x_
Lifetime_Probability_of_Developing_or_Dying_From_Cancer.asp?sitearea=&level).
So what types of cancer arise in the heart? Here, it
is important to distinguish primary tumors (arising
from the tissues of the heart) from metastatic disease
(which has spread from some other primary site into
the heart). Metastasis to the heart is relatively common
from carcinomas of the lung, breast, kidney, and liver,
as well as soft tissue sarcoma, melanoma, lymphoma,
and leukemia. In contrast, primary tumors of the heart
are rare (as noted above).
Approximately three-fourths of primary heart tumors
are considered benign. Cardiac myxoma is the most common
benign tumor, accounting for up to 30% of primary heart
tumors, and while pathologically considered a benign
tumor, myxomas can cause a variety of clinical features.
Most primary cardiac malignancies are variants of sarcomas,
with the most common being angiosarcoma (approximately
7%). The presenting symptoms for cardiac malignancies
often mimic other noncancerous cardiac conditions, and
the diagnosis may not be established until autopsy.
Therefore, a high index of suspicion is critical in
making the diagnosis.
Perhaps another interesting question is: why aren’t
cardiac malignancies more common? This question can
only really be answered with speculation. The most common
explanation is that the heart is considered a post-mitotic
organ, with little or no division of cardiac myocytes,
in contrast to the rapid turnover of epithelial tissues
in the skin, gastrointestinal tract, and other organs,
which helps to explain the higher incidence of cancers
in those organs. Currently, there is a great deal of
interest in how the heart “remodels” after
myocardial infarction, with some evidence for a role
by putative cardiac stem cells in this process. Additionally,
experimental studies suggest a role for mesenchymal
stem cells in repair of heart damage and remodeling,
so there probably are dividing cells in the heart, in
contrast to what was previously thought.
Whatever the reason, we should consider ourselves lucky
that cardiac malignancies are so rare. As stated above,
making the diagnosis is difficult. Effective therapies
are scarce. Surgical resection of the cancer is required
for cure, yet the achievement of eradication of the
cancer (i.e., “negative margins”) is usually
not possible. Indeed, long term survival is rare. And
in the end, doesn’t the heart have enough problems?
|
