Keywords:
Cancer, Radiation therapy / Oncology, PET-CT, CT, Nuclear medicine, Lung
Authors:
S. L. Kure1, M. Petersen2, T. Hansen 3; 1Tjæreborg/DK, 2Esbjerg Ø/DK, 3Vejle /DK
DOI:
10.26044/ecr2019/C-2863
Results
When defining the tumor volume using FDG PET/CT,
it is possible to escalate the mean dose from 62,8 Gy [62,5-66] to 88 Gy [74,9-134,9] without exceeding the dose restriction for the OAR.
The results also showed that even though OAR restrictions was met in the planning of the radiotherapy ,
a higher dose equals a higher risk of severe side effects from the treatment.
This despite all studies OAR restriktions was held underneath the restritions for all tissue set by QUANTEC.
However some studies explain this as a result of tumor shrinkage during the radiotherapy.
The tumor shrinkage can be taken into account with adaptive strategies,
where study four shows that the average size of the tumor volume is 54% smaller 4 weeks after the first treatment when compared to the volume before the beginning of the treatment.
Therefore there is a big risk,
that the OAR receives a significant larger dose than calculated,
if no replanning is made. This is descriped in study one,
which shows an overdose of the OAR in 37% of patients due to tumor shrinkage after ten fractions of the treatment.
These results can explain why some studies show lower survival rate and more severe side effects,
than others.
Studies shows,
that although the dose does not exceed the restrictions,
an increase in dose will still result in more side effects.
This is shown in study seven,
where the average dose is 32,2 Gy less than in study five,
and show that the amount of side effects from OAR like oesophagitis,
are considerably fever with lover dose to the tumor volume.