Hypofractionated Imrt-Igrt With Internal Markers In Prostate Cancer Treatment: Mature Results

Hypofractionated radiation therapy with IMRT-IGRT (Hypo-IMRT-IGRT) as primary treatment for PC allows reduction in overall treatment time without compromising outcomes. We report the mature results of an hypofractionated regimen in five weeks for PC. From March 2009 to July 2014, 118 patients (p) (median age, 69y range 51-84y) with PC were enrolled. NCCN risk criteria: low (n=34; 29%), intermediate (n=66; 56%) and high (n =18; 15 %) ; pretreatment PSA: median 7.5 ng/ml (range 4-81ng/ml); stage: T1(92 pts), T2a(13 pts), T2b (8 pts),T2c (4 pts), T3a(1 pt); Gleason score: 6 (58 pts), 7 (58 pts), 8 (2 pts). Two internal gold-fiducial markers were placed transperineally guided by transrectal ultrasound before treatment. CTV was contoured according to RTOG guidelines including prostate and seminal vesicles when indicated and expanded 3 mm posteriorly and 5 mm in all other direction to create PTV. All patients underwent treatment with IMRT up to a total dose of 70Gy in 28fx (2,5Gy/day) in a Novalis linac. Daily verification was performed with IGRT-Exactrac® and 6D-robotic couch; 44p (37%) received androgen deprivation. Toxicity was assessed according to RTOG/EORTC criteria. Biochemical relapse was defined according to Phoenix criteria. Institutional review board approved this study. All patients completed radiotherapy. Median follow-up: 55 months (range 24-92 months). Actuarial overall survival (OS) at 5 and 7-year: 92% and 88%, respectively (95%CI, 95-105%). For low, intermediate and high risk group, 5-year OS rates were 97%, 88%, and 80% respectively, and 7-year OS rates were 97%, 88% and 60% (p=ns). Actuarial 5 and 7 year biochemical relapse free survival (bRFS): 92% and 80% (95%IC, 81-89%) respectively. For low, intermediate and high risk group, actuarial 5 and 7 year bRFS rates were 93% and 84%, 95% and 81%, and 89% and 81% respectively. NCCN group of risk showed statistical significant differences regarding bRFS in favour of low and intermediate risk groups (Breslow p = 0.049). Grade 2 acute genitourinary (GU) toxicity was reported by 11p (9%). Maximal acute gastrointestinal (GI) toxicities were grade 1 in 1% of patients. There was no grade 3, 4 or 5 toxicity. Late toxicities were evaluated in all patients: GU toxicities grades 1, 2 and 3 were 17%, 5% and 3%; GI late toxicities were grade 1 in 3% and grade 2 in 1% of patients. No late GI higher than grade 2 has been reported. There was no Grade 4 or 5 late GU and GI events. No relationship was found between GU or GI adverse effects and any of the analyzed parameters: age, androgen deprivation or PTV volume Observed mature results are acceptable. This Hypo-IMRT with IGRT schedule for prostate radiotherapy reduces treatment length by 2 weeks as compared to other treatment regimens commonly used. Treatment is well tolerated showing encouraging rates of OS and BRFS although longer follow up is required.