Biomedical Engineering Reference
In-Depth Information
and crowd out other cells within the area. In some fortunate cases an in-
dividuals own immune system may actually stop the growth of the tumor.
The immune system may recognize that the cells within the tumor are not
normal. If this happens, the immune cells may destroy the tumor. This may
take place a number of times throughout an individuals life without them
ever being aected.
If a tumor goes unnoticed and begins to grow, lack of nutrients can
eventually limit its growth. If nutrients are not continuously supplied, the
tumor cells cannot metabolize. In this case, at the very least, no new growth
can occur. If a tumor becomes unable to grow and unable to support some
of its functions and cell death occurs, the tumor may go into a dormant
state. In this case it cannot spread. Once the tumor reaches this limiting
size, and if it is unable to get more nutrients, it will stay in this dormant
state and may eventually die o. Researchers are trying to develop tests
that will determine whether for example an individuals breast and prostate
tumors will remain dormant or spread. In that way, patients in the future
could be spared unnecessary treatments.
There are many dierent cancers and there are many dierent compo-
nents involved in the development of cancer making each person's cancer
quite unique. Further, each type of cancer (e.g., breast, colon or prostate)
does not necessarily behave like other cancers. For these reasons, there is
no one \cure for cancer." Rather there will be lots of interventions and
cures that are developed through a systematic approach and understand-
ing. Researchers are constantly looking for ways to develop screening tools
to identify cancers at their earliest phases so that they can be treated with
surgery; however, each organ needs its own individual screening tool. For
example, colon cancer is screened through a variety of techniques including
colonoscopy. Cervical cancer is screened through the Pap test, which exam-
ines scrapings of cells from the cervix and discovers cells in the early stages
of change. The mammogram is used to determine the presence of breast
cancer hopefully at an early stage, but may not detect cells in the earliest
phases of abnormal cell development prior to becoming cancerous.
The rst stage growth of cancer is called Avascular. In the avascular
state tumor growth, it has no blood vessels and relatively harmless. Its
nutrients, oxygen and glucose are obtained and it eliminates waste products
via diusion. Cells in the center starve while Cells on the periphery thrive.
Cells in the interior are quiescent, but not dead and do not divide. The
growth of the avascular tumor is limited to a few mm in diameter. In
response to an externally supplied nutrient, avascular tumors adopt a well
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