Cancer awareness has come a long way. With the pink ribbon campaigns for breast
cancer and blue ribbons prostate cancer, the general public is certainly aware of
the myriad ways to support cancer causes. But, what do we really know about
research and technology behind our awareness efforts? If we delve a little deeper
and actually see the innovative technology behind cancer treatments, we find
procedures and therapies like Intensity-Modulated Radiation Therapy, proton
therapy and gamma knife therapy.
Intensity-Modulated Radiation Therapy (IMRT)
These plates shape the photon beam to the dimensions of the tumor.
IMRT uses photons rays to control cell growth. The ionizing radiation works by
damaging the DNA of the targeted tissue. It is believed that cancer cells may be
more susceptible to death by this process because many of them lose the ability to
repair their DNA when they become cancerous. The amount of radiation used in
photon radiation therapy is measured in gray (Gy). It varies depending on the type
of the cancer being treated and it’s severity. The typical dose for a solid epithelial
tumor ranges from 60 to 80 Gy. Lymphomas are treated with 20 to 40 Gy. To avoid
healthy tissue, shaped radiation beams are aimed from several angles and intersect
at the tumor. Organs like the bladder, stomach and lungs are always expanding and
shrinking with-in the body. Unfortunately, this movement can cause the tumor to
slightly shift from the time it is mapped out and when radiation is administered.
To account for this movement a cusp of healthy tissue around the tumor is also
targeted. This area will experience the full strength of the radiation.
In a proton therapy treatment room, the beam can be delivered from any angle.
Protons are heavier than photons and, therefore, present a less scattered beam
when targeted. Protons attack the DNA of cancer cells just like photons; however,
a more streamline beam of radiation means that surrounding tissue is much less
affected. Because the damage to healthy tissue is limited, a higher dose of radiation
can be used with proton beams. Heavier doses go straight to the tumor, and there
is no exit dose past the tumor Proton therapy is especially beneficial for tumors
in or near sensitive areas. Cancer around the eyes, heart, brain or genitalia can be
dangerous to target without such a focused beam. Pediatric cancers and tumor are
also often treated with protons.
A diagram of the shape of a Gamma Knife machine
A Gamma Knife typically contains 20 cobalt-60 sources of approximately 30 curies.
These sources are mounted in a circular formation inside a heavily shielded helmet.
Each one of the sources delivers a beam of gamma rays. The helmet that the patient
is wearing is surgically attached. This guarantees that the brain, and consequently
the tumor, will stay in exactly the same place through the treatment. The gamma
rays are targeted at the tumor very precisely. Each ray itself is a fairly low amount
of radiation. Combined, however, the rays have a powerful impact on the targeted
area. The surrounding brain tissue does have radiation passing through. Because
the system produces so many rays, the strength of each one can be diminished. It’s
hopeful that the healthy issue is not negatively affected.