Dose-intensified versus conventional dose-salvage radiotherapy for biochemically recurrent prostate cancer after prostatectomy: Six-year outcomes of the SAKK 09/10 randomized phase III trial.
Authors: Ghadjar Pirus , Hayoz Stefanie , Bernhard Juerg , Zwahlen Daniel Rudolf , Hoelscher Tobias , Gut Philipp , Polat Bülent , Hildebrandt Guido , Mueller Arndt-Christian , Plasswilm Ludwig , Papachristofilou Alexandros , Schaer Corinne , Sumila Marcin , Zaugg Kathrin , Guckenberger Matthias , Ost Piet , Reuter Christiane , Bosetti Davide Giovanni , Khanfir Kaouthar , Aebersold Daniel M. 
Published: March 2021

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Background: Salvage radiotherapy (RT) is often utilized in case of biochemical progression after radical prostatectomy (RP). Here we report the outcomes of the European SAKK 09/10 randomized phase 3 trial with the aim to compare effectiveness and tolerability of conventional vs. dose-intensified salvage RT. Methods: SAKK 09/10 is an open-label, multicenter, randomized phase 3 trial performed in 24 centers in Switzerland, Germany and Belgium. Men with biochemical progression (two consecutive rises with the final PSA > 0.1 ng/mL or three consecutive rises) after RP with a PSA nadir of ≤ 0.4 ng/mL, with a PSA ≤ 2 ng/mL at randomization and without clinical evidence of macroscopic disease were recruited. Patients were randomly assigned to either conventional dose RT (64 Gy in 32 fractions) or dose-intensified RT (70 Gy in 35 fractions) directed to the prostate bed. Three-dimensional conformal RTor intensity-modulated RT/rotational techniques were used. The primary endpoint was freedom from biochemical progression (PSA ≥ 0.4 ng/mL and rising). Secondary endpoints included clinical progression-free survival, time to hormonal treatment, overall survival, acute and late toxicity (according to the NCI CTCAE v4.0) and quality of life (according to the EORTC QLQ-C30 and PR25). The trial was registered under NCT01272050 in clinicaltrials.gov. Results: Between 02/2011 and 04/2014, 350 patients were randomly assigned to 64 Gy (n = 175) or 70 Gy (n = 175), of whom 344 aged between 48 to 75 years were assessable for the intention-to-treat population. The median PSA at randomization was 0.3 ng/mL (range, 0.03-1.61 ng/mL). At the time of data cutoff (July 3, 2020), the median follow-up was 6.2 years (IQR 5.5-7.2) and a total of 138 biochemical progression events occurred. The estimated freedom from biochemical progression rate at 6 years was 62.3% (95% CI 54.2-69.4%) and 61.3% (95% CI 53.4-68.3%) for the 64 Gy and the 70 Gy arm, respectively, and the hazard ratio adjusted by stratification factors was 1.14 (95% CI 0.82-1.60; log-rank p = 0.44). No significant difference was found for clinical progression-free survival, time to hormonal treatment and overall survival between the two arms, respectively. Late grade 2 and 3 genitourinary toxicity was observed in 35 (21.2%) and 13 (7.9%) patients treated with 64 Gy, and in 46 (26.3%) and 7 (4%) patients with 70 Gy (p = 0.81). Lategrade 2 and 3 gastrointestinal toxicity was observed in 12 (7.3%) and 7 (4.2%) patients with 64 Gy, and in 35 (20%) and 4 (2.3%) patients with 70 Gy(p = 0.009). Quality of life data will be presented. Conclusions: Dose-intensified salvage RT to the prostate bed was not superior to conventional dose RT. However, dose-intensified salvage RT was associated with higher frequencies of late grade ≥ 2 gastrointestinal toxicity. Clinical trial information: NCT01272050.