Biomedical Engineering Reference
In-Depth Information
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Figure 1.5
Illustration of how anticancer therapy can lead to reduction, resistance,
recapitulation, and relapse of the cancer. It is analogous to immuno-
surveillance's elimination, equilibrium, and escape.
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multiply to repopulate the tumor. Recapitulation of the heterogeneous
population occurs by phenotypic expansion. Finally, a resistant and aggressive
cancer will be capable of relapse and metastasis.
1.4 Revolution
In 1962, Thomas Kuhn wrote a topic about paradigms and scientific
revolution.
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Right now we are in a state of collecting knowledge, with only
slow improvements in targeted drug delivery occurring. One can hope that a
shift of paradigm can be a catalyst for a massive leap forward in targeted drug
delivery. That may mean abandoning, or at least not using too broadly, the
terminology of targeted drug delivery. A more accurate description for some
targeted designs may be ''affinity therapy'', which was used over 30 years
ago.
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When about 5% or less of the injected dose gets to the targeted tumor
in the clinical setting, it is clear that existing dogma needs to be questioned.
It may be possible to provide something close to a magic bullet since
monoclonal antibody formulations of Zevalin
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and BEXXAR
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have reached
the market after showing effects in clinical trials. However, it must be
recognized that these therapies are directed towards cancer cells circulating in
the blood stream. This environment is discrete compared to cancer cells in solid
tumors, as the therapeutic begins with 100% bioavailability in the blood and
flow encourages contact. Worth noting is the approval of Trastuzumab
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that
has been approved for HER2-positive breast cancer. However, access is still
unique as it is approved for treating metastatic cancer or as an adjuvant
therapy. Thus, changing the focus of the targeting might be considered. It may
be better to focus on changing the tumor environment or implementing
immunomodulation to induce a state where the body can combat the cancer
with its own resources.
