Exclusive image guided IMRT vs. radical prostatectomy followed by postoperative IMRT for localized prostate cancer: a matched-pair analysis based on risk-groups

135 Background: To investigate whether patients treated for a localized prostate cancer require prior radical prostatectomy followed by postoperative radiotherapy or exclusive radiotherapy, in the modern era of image-guided IMRT. METHODS One hundred and seventy-eight patients with localized prostate cancer were referred for daily on-line exclusive image-guided IMRT (IG-IMRT), while 69 patients were referred for postoperative IMRT without image guidance after radical prostatectomy (RP+IMRT). The patients were matched in a 1:1 ratio according to their baseline risk group before any treatment. Late toxicity was scored using the CTV v3.0 scale. Biochemical failure was defined as a postoperative PSA ≥ 0.1 ng/mL followed by 1 consecutive rise in PSA for the postoperative group of patients and by the Phoenix definition (nadir+2 ng/mL) for the group of patients treated with exclusive radiotherapy. RESULTS A total of 98 patients were matched (49:49). Thirty patients had a low-risk (30.6%), 62 patients an intermediate risk (63.3%) and 6 patients a high risk (6.1%). In the RP+IMRT group, the median PSA value before radiotherapy in the RP+IMRT group was 0.28 ng/mL [undetectable-6.99]. The median radiation dose in the IG-IMRT group was 77.4Gy [73.0-79.8 Gy] whereas it was 66.0 Gy [31.4-70.3 Gy] in the RP+IMRT group. The duration of the hormones was similar in both groups (p= 0.438). From the start of any treatment, the median follow-up was 56.6 months (95% CI = [49.6-61.2], range [18.2-115.1]. No patients had late gastrointestinal grade ≥ 2 toxicity in the IG-IMRT group vs. 4% in the RP+IMRT group. Forty-two percent of the patients in both groups had late grade ≥ 2 genitourinary toxicity. The 5-year freedom from biochemical failure rates in the IG-IMRT group and in the RP+IMRT groups were 93.1% [80.0-97.8] and 76.5% [58.3-87.5], respectively (p= 0.031). CONCLUSIONS Patients with localized prostate cancer treated with IG-IMRT had a better oncological outcome than patients treated with RP+IMRT. Further improvements in postoperative IMRT using image guidance and dose escalation need to be evaluated to determine whether it could eventually be superior to IG-IMRT.