22 research outputs found
Assessment and topographic characterization of locoregional recurrences in head and neck tumours
Purpose:
To evaluate the differences between three methods of classification of recurrences in patients with head
and neck tumours treated with Radiation Therapy (RT).
Materials and methods:
367 patients with head and neck tumours were included in the study. Tumour
recurrences were delineated in the CT images taken during patient follow-up and deformable registration was used
to transfer this volume into the planning CT. The methods used to classify recurrences were:
methodCTV
quantified
the intersection volume between the recurrence and the Clinical Target Volume (CTV);
methodTV
quantified the
intersection between the Treated Volume and the recurrence (for method CTV and TV, recurrences were classified
in-field if more than 95% of their volume were inside the volume of interest, marginal if the intersection was
between 20-95% and outfield otherwise); and
methodCOM
was based on the position of the Centre Of Mass of the
recurrence. A dose assessment in the recurrence volume was also made.
Results:
The 2-year Kaplan-Meier locoregional recurrence incidence was 10%. Tumour recurrences occurred in 22
patients in a mean time of 16.5 ± 9.4 months resulting in 28 recurrence volumes. The percentage of in-field recurrences
for methods CTV, TV and COM was 7%, 43% and 50%, respectively. Agreement between the three methods in
characterizing individually in-field and marginal recurrences was found only in six cases. Methods CTV and COM agreed
in 14. The percentage of outfield recurrences was 29% using all methods. For local recurrences (in-field or marginal to
gross disease) the average difference between the prescribed dose and
D
98%
in the recurrence volume was -5.2 ± 3.5%
(range: -10.1%-0.9%).
Conclusions:
The classification of in-field and marginal recurrences is very dependent on the method used to
characterize recurrences. Using methods TV and COM the largest percentage of tumour recurrences occurred in-field in
tissues irradiated with high doses.
Keywords:
Head and neck tumours, Radiation therapy, Characterization of tumour recurrences, Geometric methods,
Dosimetric assessmen