112 / 1096
S99
ESTRO 36
_______________________________________________________________________________________________
radiotherapy is harnessed to convert the tumor into an
individualized cancer vaccine. Overall, while radiation has
emerged as a promising partner for immunotherapy and
current research is focusing at identifying tumor and
patient characteristics that can predict which patients
should receive upfront the combination of immunotherapy
with radiotherapy instead of immunotherapy alone.
SP-0193 Quality improvement in radiotherapy:
history, significance and impact of dosimetry audits
J. Izewska
1
1
IAEA - International Atomic Energy Agency, Dosimetry
and Medical Radiation Physics Section, Vienna, Austria
The concept of verification of radiation doses in medical
applications was introduced in early 20th century, not long
after radiation started to be used for treating cancer.
Initially, to estimate the adequate daily fraction of
radiation to be given to patients physicians exposed the
skin of their own arms to radiation to produce the
‘erythema dose’. Since then, the methodologies, dose
measurement tools and radiation therapy equipment have
made a great progress. In 1925 R. Sievert established a
circulating physical department for standardizing the
Roentgen radiation used in cancer therapy in Sweden. The
department found some unreliable dose meters and
identified the need for better protective equipment. At
the same time, the measurements of percentage depth
doses collected during the visits were used as a reference
dataset for the Roentgen facilities in Sweden. Another
example of early dosimetry audits was documented in
Poland; following the idea by Marie Curie, the
Measurement Laboratory was established in 1936 for
radiation dose measurements at Polish hospitals using
radium and
X-ray
beams.
The Dosimetry Laboratory of the International Atomic
Energy Agency (IAEA) was set up in early 1960s with the
aim of the provision of dosimetry audits for radiotherapy
centres worldwide and for ensuring international
consistency in radiation dosimetry. First trial inter-
hospital comparisons were implemented by the IAEA in
1965–1966. In parallel, dosimetry comparisons of Co-60
and high energy beams from early medical accelerators
were conducted among hospitals of France, Sweden, and
in other countries. In USA, the Radiological Physics Center
was established in 1968 to operate as an independent
quality assurance office for multi-institutional cooperative
group clinical trials.
Since 1969, the calibration of radiotherapy beams in 2200
hospitals in 132 countries has been verified by the IAEA
jointly with the World Health Organization (WHO) through
postal dosimetry audits. One important part of the
auditing process is related to resolving dosimetry
discrepancies occurring in the audit; errors are traced,
analysed and corrected. In early years, only approximately
50% audited centres had the acceptable beam calibration.
Over the time, several radiotherapy centres improved
their practices, and the current percentage of acceptable
results exceeds 97%.
With the development of advanced radiotherapy
technologies resulting in greater complexity of radiation
treatments, it was necessary to extend basic dosimetry
audits. More complex audit programmes involve tests of
different beam parameters, machine performance
characteristics and treatment delivery techniques.
Examples include audits of small beam dosimetry,
complex irradiations, combined beams, audits of
treatment planning, and ‘end-to-end’ methodologies.
Although the accurate clinical dosimetry is essential for
the effective radiation treatment, the desired patient
outcome cannot be achieved without the adequate quality
of clinical, physical and technical processes. A
comprehensive IAEA audit methodology called the Quality
Assurance Team for Radiation Oncology (QUATRO) was
developed to review the entire radiotherapy chain and
infrastructure. Since 2005 QUATRO audits have been
conducted in approximately 90 radiotherapy centres in
various world regions.
The experiences above demonstrate that quality audits
improve dosimetry and clinical practices. Audits have
been effective in identifying discrepancies in dosimetry
and in providing support to participating centres in
resolving them. Audits can lessen the likelihood of major
dosimetry errors and the resulting consequences for
patient outcomes. Audits also address smaller errors and
help in reducing uncertainties in the dose delivery thus
improving the treatment quality for many patients. Audits
can provide support and confidence when introducing new
technologies and complex processes in radiotherapy.
Audits verify the consistency of dosimetry practices among
centres in different countries and world regions. They
strengthen the confidence in clinical dosimetry both for
physicists and clinicians who obtain assurance that their
patients are given accurate doses in accordance with
medical prescription.
The significance of quality audits in radiotherapy and their
impact on dosimetry and clinical practices have been
widely recognized. Still, a large number of radiotherapy
centres do not participate in such audit programmes. Due
to obvious benefits, all centres should be encouraged to
take part in quality audits in radiotherapy.