Ultrahypofractionated CyberKnifeTM based stereotactic radiotherapy versus conventional radiotherapy in patients with prostate cancer - acute toxicity evaluation in two phase II prospective studies.

Our purpose was to compare the acute toxicity of ultrahypofractionated CyberKnife (TM) based stereotactic radiotherapy (SBRT Arm) and conventional radiotherapy (EBRT Arm) in prostate cancer patients. Two-hundred-sixteen men with prostate cancer were enrolled in our prospective studies. One-hundred and nine were irradiated using CyberKnife to total dose of 36,25 Gy in 5 fractions. One-hundred and seven were irradiated conventionally to total dose of 76 Gy in 38 fractions. Mean age of patients was 69. Acute genitourinary (GU) and gastrointestinal (GI) adverse-events were collected. The maximal acute toxicity EORTC/RTOG score was assumed. A total of 41%, 44%, 12% and 3% of patients presented grade 0, 1,2 and 3 acute genitourinary toxicity in SBRT arm, respectively. A total of 21%, 33%, 43% and 3% of patients demonstrated acute grade 0, 1,2 and 3 genitourinary toxicity in EBRT arm. A significant difference between number of patients with grade 2 GU toxicity was observed (p-0.000) and between patients without any toxicity (p-0.0017). A significant difference in frequency of acute GI toxicity between both groups was observed, too. 71% vs. 44% had no toxicity (p-0.0001), and 3% vs. 18% (p-0.0004) presented grade 2 GI toxicity in SBRT and EBRT arms respectively. The acute toxicity rates of fractionated stereotactic radiotherapy is lower compared to conventional irradiation.