Time-Course and Accumulated Risk of Severe Urinary Adverse Events after High vs. Low Dose Rate Prostate Brachytherapy with or Without External Beam Radiation
Menée à partir des données des registres américains des cancers portant sur 24 396 patients atteints d'un cancer de la prostate non métastatique (âge : supérieur ou égal à 65 ans ; durée médiane de suivi : 4,3 ans), cette étude compare la toxicité urinaire à long terme d'une curiethérapie à haut débit et d'une curiethérapie à bas débit, en combinaison ou non avec une radiothérapie externe
Introduction : Severe urinary adverse events (UAEs) include surgical treatment of urethral stricture, urinary incontinence and radiation cystitis. We compared the incidence of CTCAE grade 3 UAEs after low dose rate (LDR) and high dose rate (HDR) brachytherapy as well as LDR+EBRT and HDR+EBRT. Methods : Men aged ≥65 years with non-metastatic prostate cancer were identified from SEER-Medicare who were treated with LDR (n=12801), HDR (n=685), LDR+EBRT (8518) and HDR+EBRT (n=2392). The populations were balanced by propensity weighting and the Kaplan-Meier incidence of severe UAEs was compared. Propensity-weighted Cox proportional hazards models were used to compare the adjusted hazard of UAEs. These UAEs were compared to a cohort of men not treated for prostate cancer. Results : Median follow-up was 4.3 years. At 8 years, the propensity weighted cumulative UAE incidence was highest after HDR+EBRT (26.6% (95% Confidence Interval: 23.8%-29.7%)) and lowest after LDR (15.7% (95% CI: 14.8%-16.6%))). The absolute excess risk over non-treated controls at 8 years was 1.9%, 3.8%, 8.4% and 12.9% for the LDR, HDR, LDR + EBRT, and HDR + EBRT respectively. This represents a number needed to harm of 53, 26, 12, and 8 persons. The additional risk for developing a UAE related to treatment for LDR, LDR+EBRT, and HDR+EBRT, was greatest within the 2 years following treatment, and then continued to decline over time. Beyond 4 years, the risk of developing a new severe UAE matched the baseline risk of the control population for all treatments. Conclusion : Toxicity differences were observed between LDR and HDR, but differences did not meet statistical significance. However, combination radiotherapy (either HDR+EBRT or LDR+EBRT) increases the risk of severe UAEs compared to HDR alone or LDR alone. The highest increased risk of urinary toxicity occurs within the 2 years following therapy, and then declines to approximately 1% increase in incidence per year.