Calculation of planning target volume margins using the van Herk, Stroom and ICRU methods in patients with gastric cancer

Abstract

Author(s): Agnieszka Namysł-Kaletka, Andrzej Tukiendorf, Jerzy Wydmański

The aim. The aim of this paper was to compare the methods of specifying margins in
patients with gastric cancer.
Material and methods. The material included 57 patients with gastric cancer during
chemoradiotherapy in whom the positioning in the therapeutic system was verified using
2 kV images prior to each radiotherapy fraction. Subsequently, shifts in three axes were
assessed. Based on the shifts obtained, systematic and random errors were calculated
in given axes and margins were specified using the van Herk, Stroom and ICRU 62
formulae.
Results. The margins resulting from the interfraction motion based of the van Herk,
Stroom and ICRU formulae were as follows: 9 mm, 7 mm and 6 mm in the lateral axis,
16 mm, 14 mm and 11 mm in the craniocaudal axis as well as 8 mm, 7 mm and 5 mm
in the anteroposterior axis, respectively for each formula. The lowest percentage of shifts
that were greater than the calculated margin was observed in the van Herk method (1.5%
in the lateral axis, 3.3% in the craniocaudal axis and 1.9% in the anteroposterior axis).
Conclusions. Based on the material investigated, the margin recommended for centers
in which daily patient position verification is not possible is the one calculated with
the use of the van Herk formula.

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