Extension of prostate bed salvage radiotherapy (PBRT) with pelvic irradiation (PLNRT), in combination with short-term androgen deprivation therapy (ADT), reduced prostate cancer progression after 5 years in the SPPORT trial.
Between 2008 and 2015, 1,792 patients were enrolled and randomized to 3 groups: 592 to group 1 (PBRT only), 602 to group 2 (PBRT plus ADT) and 598 to group 3 (PLNRT plus PBRT plus ADT). At the interim analysis (n = 1,191; May 23, 2018), the Haybittle-Peto threshold for 5-year progression-free survival (PFS) was exceeded in a comparison between Group 1 and Group 3 (difference 17.9%; SE 2, 9%; p < 0.0001). The difference between groups 2 and 3 did not exceed the limit (p = 0.0063). At the final analysis (May 26, 2021) with a median follow-up among survivors of 8.2 years (IQR 6.6-9.4), the 5-year PFS rate was 70.9% (95% CI 67.0-74.9) in Group 1; 81.3% (78.0-84.6) in group 2 and 87.4% (84.7-90.2) in group 3. The PFS in group 3 was therefore superior to groups 1 and 2.
Acute (≤ 3 months after radiotherapy) grade 2 adverse events occurred significantly more frequently in group 3 (246 (44%) of 563) than in group 2 (201 (36%) of 563; p = 0.0034), and that percentage was higher than in group 1 (98 (18%) of 547; p 3 months after radiotherapy) did not differ significantly between groups, except for more late grade 2 blood or bone marrow events in group 3 versus group 2 (one-sided p = 0.0060).
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