Division of Biomedical Physics in Radiation Oncology
Prof. Dr. Joao Seco
Biological effective Ion Dose producing DNA Damage
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Radiation therapy is the most common treatment for cancer, being used in approximately 70% of all cancers either alone or
combined with surgery or chemotherapy. It uses high-energy particles or waves, such as x-rays, gamma rays, electron beams,
protons, carbon ions, to "kill" or "damage" cancer cells. There is a growing interest in the use of ion-beams (protons, carbon ions)
for cancer therapy. The principal benefit of ion-beams are there finite range (or depth) in tissue, known as Bragg peak, where a
significant amount of the radiation is deposited at the end of the track where the ions stop. The Bragg peak guarantees that
healthy organs distal (deeper) to this peak receive NO radiation, reducing significantly side effects.
However, due to treatment planning and beam delivery uncertainties, it is not possible to place accurately the Bragg peak on
the distal end of the tumor. Thus, we voluntarily irradiate healthy surrounding organs to guarantee the tumor receives the
correct radiation dose. The Bragg peak “uncertainty” reduces the clinical potential of ion-beam radiotherapy, because of the
additional radiation given to healthy organs.
My Current Research interests are:
1) to develop novel imaging technologies to reduce the Bragg peak positioning "uncertainties" for ion-beam radiotherapy,
using Helium beam imaging and prompt gamma spectroscopy.
2) to investigate the mechanism of radiation triggered DNA damage via reactive oxygen species (ROS).
In principle, ion-beam therapy offers a substantial clinical advantage over conventional photon therapy. This is because of the
unique Bragg peak depth-dose characteristics, which can be exploited to achieve significant reductions in normal tissue doses
proximal and distal to the target volume. These may, in turn, allow escalation of tumor doses and greater sparing of normal
tissues, thus potentially improving local control and survival while at the same time reducing toxicity and improving quality of
life.
In the future, a more widespread use of ion-beam radiotherapy will make it possible to significantly improve cancer survival with
minimal side effects. However, in order to take full advantage ion-beam radiotherapy a better control is needed of the Bragg
peak within the patient (cancer) and a better understanding of the radiation triggered DNA damage is required. Once we can
control very accurately the positioning of the Bragg peak within the cancer to within 1mm, then it will be possible to reduce
radiation side-effects, while simultaneously boosting the cancer with more radiation.
