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Purpose: A much debated topic in prostate cancer therapy concerns the correct timing of radiotherapy (RT) in subjects undergoing radical prostatectomy. Recently, Radicals-RT trial showed comparable results between patients undergoing adjuvant RT, immediately after surgery, and those undergoing salvage radiotherapy at the time of a biochemical relapse. The purpose of our work is to verify the thesis supported by the RADICALS study in order to investigate the best timing to plan post-operative radiotherapy.

Material and Methods: We conducted a retrospective study on 249 patients with operated prostate cancer (prostatectomy alone or prostatectomy plus lymphadenectomy) divided according to postoperative PSA in three groups: a first group of 40 patients with postoperative PSA> 0.5 ng / ml; a second group of 209 patients with postoperative PSA < 0.5 ng / ml; within this second group there was a further subgroup of 165 patients with postoperative PSA < 0.2 ng / ml. All patients were studied according to the following criteria: Gleason Score, age, type of surgery, risk class, PSA at diagnosis, postoperative PSA, number of lymph nodes removed, pTNM and margin status. From January 2011 to December 2019, all these 249 subjects underwent RT: 158 patients were treated with adjuvant RT (135 only on the prostate lodge and 23 on the lodge and lymph node drainages), and 91 with salvage RT (77 only on the prostate lodge and 14 on prostatic lodge and lymph node drainages). All patients were treated on the prostate bed (70-72 Gy using a standard regimen or 63-65.80 Gy using a hypofractionated regimen) and only selected patients in on lymph node drains chains (50.40 Gy in 28 fractions with possible boost up to 65.80 Gy on positive lymph nodes). The median follow-up was 63 months (Range 18-116 months).

Results: We did a multivariate analysis of Progression Free Survival factors risk by step-wise method finding: in the group of all 249 patients for those with adjuvant RT group vs rescue RT HR = 3,195 ( 95% CI: 1,534-6,655 with p= 0,002). In the group of PSA < 0.5ng/ml for those with adjuvant RT group vs rescue RT HR= 3,763 ( 95% CI: 1,509-9,380 with p=0,004). In the last group of PSA < 0.2ng/ml, the p-value was 0.35.

Conclusion: These results show a similar trend between adjuvant RT and salvage RT only in subjects with postoperative PSA < 0.2 ng / ml, while, in other populations, the adjuvant RT has a better outcome. In light of these results, salvage radiotherapy should be planned as soon as the PSA value exceeds 0.2 ng / mL.