Comparison of the conventional ‘box technique’ with two different ‘conformal’ beam arrangements for prostate cancer treatment

Summary To quantify the possible advantages arising from the use of ‘conformal’ radiotherapy of localized prostate cancer, and to compare the dose distributions obtained with two different ‘conformal’ techniques. Twelve patients with localized prostate cancer were enrolled in the study. For each patient, three techniques were planned: the standard ‘box technique’ (A), a four-fields ‘conformal’ technique (B), and a 6-fields conformal technique (C). For each of the 36 3D plans, dose-volume histograms (DVH) were obtained, along with the mean, maximum and minimum doses for the clinical and planning target volumes (CTV, PTV) for the rectum, the bladder, and the femoral heads. The resulting data were compared. On average, the standard technique resulted in the exposure of a significantly larger bladder volume to the higher doses; a similar, but less remarkable difference has been observed for the rectal volume. The coverage of the PTV appears to be significantly more homogeneous with the two conformal techniques. The results presented here add to the evidence available in the literature and suggest a possible advantage of both the conformal techniques over the standard ‘box technique’ for the treatment of localized prostate cancer. The 6-field conformal technique does not seem superior to the four field one. Évaluer les avantages d'une radiothérapie conformationelle dans le cancer de la prostate de stade limité et comparer les distributions de doses obtenues par deux techniques différentes d'irradiation conformationelle. Douze patients traités pour un cancer de la prostate de stade limité ont été inclus dans l'étude. Pour chaque patient, nous avons étudié trois techniques: la technique standard « en boite(A), une technique de conformation à quatre champs (B) et une technique de conformation à six champs (C). Pour chaque plan dosimétrique, nous avons obtenu des histogrammes dose-volume et la détermination des doses moyennes, maximale et minimale, delivrées dans le volume cible clinique (CTV), le volume cible anatomoclinique (PTV), le rectum, dans la vessie et les têtes fémorales. La technique standard délivre une dose plus elevée dans un volume plus grand de vessie et de rectum que les techniques de conformation. Les deux techniques de conformation assurent une distribution de dose plus homogène dans le PTV que la technique standard. Nos résultats suggèrent la supériorité des techniques de conformation sur la technique standard « en boitedans le traitement du can