[Prostate cancer boost using high-dose-rate brachytherapy: impact of the learning curve on the dosimetry]. / Curiethérapie de haut débit de dose après radiothérapie externe d'un cancer de prostate : impact de la courbe d'apprentissage sur la dosimétrie.

ABSTRACT

PURPOSE: To analyse the influence of the learning curve on dosimetric data for high-dose-rate brachytherapy prostate cancer boost. PATIENTS AND METHODS: From February 2009 to May 2012, after a first course of external beam radiation therapy (46Gy/23 fractions), 124 patients underwent high-dose-rate brachytherapy boost using Plato™ (Nucletron, an Elekta company, Elekta AB, Stockholm, Sweden). The impact of the learning curve on the dosimetric quality of the prostate implant was assessed. The dosimetric data have been analysed clinical target volume (CTV), D90 (dose to 90 % of CTV), D100, V100 (part on the CTV receiving 100 % of the dose), V150, V200 and DHI (dose non-homogeneity index). The doses delivered to 0.1, 1 and 2 cm(3) of the rectum and urethra were calculated. RESULTS: During the study period (39 months), a significant reduction of V150 (P<0.001), V200 (P<0.001), D0.1rectum (P<0.001), D1rectum (P<0.001), D2rectum (P<0.001), D0.1urethra (P<0.001), and D1urethra (P<0.002) was observed associated with a significant degradation of the D90 (P<0.001) but not significant for the V100 (P=0.29) and the D100 (P=0.3). CONCLUSION: This study confirms that the dosimetric quality of high-dose-rate brachytherapy prostate implant is significantly improved during the learning curve period.