LIFE01200604005 Shri Somnath Ghosh - Homi Bhabha National ...

CHAPTER 1
INTRODUCTION
tumor cell killing, clinicians use hyper fractionation and hypofractionation regimens,
depending on the type and radioresistance of the tumors and the nature of the surrounding
normal tissues. However, as a result of the repeated doses of radiation delivered to the
tumor cells, it results in an adaptive response in them, leading to the development of
induced radioresistance, rendering the tumor refractory to subsequent doses of radiation.
Several new approaches to radiation therapy are being evaluated to determine their
effectiveness in treating cancer. One such investigational approach is particle beam
radiation therapy. This type of therapy differs from photon radiotherapy in that it involves
the use of fast-moving charged particles to treat localized cancers. This mode has two
major advantages over conventional radiotherapy. First, because of the high LET, the
damage produced is much more and hence the tumor cell eradication is greatly enhanced.
The second advantage is that the energy deposition by the charged particles is highly
localized in a particular depth in the tissue. This is called the Bragg Peak, which confers
that advantage of selective, localized irradiation of the tumor tissue and the surrounding
normal cells are spared.
Though radiotherapy is a prime modality of cancer treatment, a major obstacle in its
successful execution is the development of radioresistance in tumor cells following
treatment. One of the factors contributing to the development of radioresistance is the
activation of the signaling molecules following irradiation. Modulation of these activated
signaling molecules with a view to overcome radioresistance could perhaps be an
effective approach.
36