Data di Pubblicazione:
2011
Citazione:
Neutrons for medicine / V. Conti ; coordinatore: M. Bersanelli ; tutore: S. Riboldi. Università degli Studi di Milano, 2011 Sep 06. 22. ciclo, Anno Accademico 2009.
Abstract:
There are a lot of definitions of cancer: in a few words one could say that it represents
a group of diseases characterized by the growth and uncontrolled diffusion
of abnormal cells. Considering the number of deaths at the world level in 2005
(50 millions), cancer is responsible of 7.6 millions (that is 13%) with an expected
increase to 11.4 millions in 2030. The innovations in the field of radiotherapy,
chemotherapy, surgery and their combined applications have allowed to maintain
these numbers under control.
Radiation therapy has been used for the treatment of cancer and other diseases
for approximately 100 years. As early as 1897, two years after the discovery by
Wilhelm Conrad Rontgen, it was concluded that X-rays could be used for therapeutic
as well as diagnostic purposes. But nearly 30 years were necessary to make
radiotherapy world wide diffused: in fact, X-rays moved into clinical therapeutic
routine only in the early 1920s.
Since the first uses of radiation to treat cancer, important changes have been made
in this field and several developments have been accomplished, both from the instrumental
(new types of linear accelerators to generate higher energy radiation
beams) and medical (different types of ionizing radiation and progress in treatment
planning) points of view.
On the other hand there is a series of tumours whose survival curve has not varied
in time both in absolute and incremental terms: extended tumours (such as the
ones of stomach, liver and lung), tumours localized near or in vital organs (such
as the glioblastoma multiforme (GBM) in the brain), radioresistant tumours (such
as melanoma). The research for new ways of treatment, together with the discovery
of neutrons in 1932 and the studies concerning their properties, inspired in
the American biophysicist G. L. Locher in 1936 the attempt to use neutron beams
in radiotherapy in the so-called NCT (Neutron Capture Therapy) first and BNCT
(Boron Neutron Capture Therapy) then. BNCT could (and the conditional is a
must) represent a hope for all the cases still lacking a survival improvement.
BNCT is a technique that in principle joins the localization capability of radiotherapy
and the specificity of chemotherapy, allowing a selective release of the
dose only to cancer cells, without damaging the surrounding healthy tissues. This
technique is based on the irradiation with thermal and epithermal neutrons of a
boronated compound (the so called carrier) selectively concentrated in tumor cells.
Following the capture of a neutron, the 10B isotope emits high LET particles (an
and a 7Li ion) that release their whole energy in the cell where the boron atom
was present at the moment of the irradiation.
The first BNCT experimental treatments were performed during the '50s. Since
then, BNCT has met ups and downs in its history because of a physical and a biological
reason: from the physical point of view, the features of the neutron beam
(a flux >5 X 108 n cm-2 s-1 with an energy <10 keV) identify nuclear reactors
as the only adequate sources; from the biological point of view, the carriers that
bring the 10B inside the cell are not selective but exploit the greater metabolism
of the cancer cells with respect to the healthy ones. BNCT has been performed
in nuclear reactors in the United States (MIT, WSU), in Japan (KURRI, JRR-4),
in Argentina (RA-6), in Europe (JRC - the Netherlands, Medical AB - Sweden,
FiR1 - Finland) for activities of Phase I (toxicity) and of Phase II (ef_cacy); no
center has started a Phase III protocol (BNCT tests randomized with respect to the
standard techniques). Possible patients for BNCT treatments have to submit the
request for the therapy to the International Ethic Committee who analyzes
Tipologia IRIS:
Tesi di dottorato
Keywords:
neutron ; proteins
Elenco autori:
V. Conti
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