Moderate Hypofractionated Protracted Radiotherapy and Dose Escalation for Prostate Cancer: Does Dose and Overall Treatment Time Matter?
Menée à partir de données portant sur 163 patients atteints d'un cancer de la prostate de stade cT1c à T3a avec risque d'envahissement ganglionnaire inférieur ou égal à 20% selon le système d'indice "Roach" (durée médiane de suivi : 80,2 mois ou 56,5 mois selon le traitement), cette étude évalue la toxicité de deux schémas de radiothérapie hypofractionnée avec modulation d'intensité
Résumé en anglais
Purpose : This is a retrospective study on two sequential dose escalation regimens of twice weekly 4 Gy/fractions hypofractionated intensity-modulated radiotherapy (IMRT): 56 Gy and 60 Gy delivered within a protracted overall treatment time (OTT) of 6.5 and 7 weeks, respectively.
Materials/Methods : 163 prostate cancer patients with cT1c-T3a disease and nodal involvement risk ≤20% (Roach index) were treated twice-weekly to the prostate +/- seminal vesicles with two sequential dose-escalated IMRT schedules: 56 Gy (14 x 4 Gy, n=81) from 2003 to 2007 and 60 Gy (15 x 4 Gy, n=82) from 2006 to 2010. Patient repositioning was made with bone-matching on portal images. Gastrointestinal (GI) and genitourinary (GU) toxicities were scored using the CTCAE v3.0 grading scale.
Results : There were no significant differences regarding the acute GU and GI toxicities in the two dose groups. The median follow-up time was 80.2 months (range, 4.5-121) and 56.5 months (range, 1.4-91.2) for patients treated to 56 and 60 Gy, respectively. The 5-year grade ≥2 late GU toxicity-free survival with 56 Gy and 60 Gy was 96±2.3% and 78.2±5.1% (p=0.001), respectively. The 5-year grade ≥2 late GI toxicity-free survival with 56 Gy and 60 Gy was 98.6±1.3% and 85.1±4.5% (p=0.005), respectively. Patients treated with 56 Gy showed a 5-year biochemical progression-free survival (bPFS) of 80.8±4.7%, worse than patients treated with 60 Gy (93.2±3.9%, p=0.007). A trend for a better 5-year distant metastasis-free survival was observed among patients treated in the high-dose group (95.3±2.7% vs. 100%, p=0.073, respectively). On multivariate analysis, only the 60 Gy group predicted for a better bPFS (p=0.016, HR=4.58).
Conclusions : A single 4-Gy additional fraction in patients treated with a hypofractionated protracted IMRT schedule of 14x4 Gy resulted in a similar and minimal acute toxicity, in worse moderate to severe urinary and GI late effects, but a significantly better biochemical control.
