Session Item

The comparison of the outcome of patients treated with stereotactic radiotherapy (SBRT) on LINAC and CyberKnife (CK) was performed.

Retrospective analysis of low/intermediate-risk prostate cancer patients treated with SBRT was performed. SBRT was delivered to the whole prostate with fraction dose of 7.25Gy and total dose of 36.25Gy, either on CK or LINAC. From the group of 601 CK patients we identified 244 with at least 2.5 years of follow-up (or previously deceased) and complete clinical history. This group was included into Prospensity Score Matching (PSM) with 19 LINAC patients. The discrepancies between the number of patients treated with each method was due to the preferable CK treatment according to our protocol, which started to change in recent years. PSM was performed with 2:1ratio (resulting in groups of 38 CK and 19 LINAC) and the variables taken into account were:age, Gleason score, PSA, TNM and prostate volume. Toxicity between groups was compared using the Fisher’s Exact Test. Progression-free survival(PFS) was defined as local/distant failure or death of the patient. Survival was evaluated with the Kaplan-Meier method and compared using the log-rank test. Early (up to 4 months after SBRT), intermediate (about 1 year after SBRT) and late (about 2 years after SBRT) toxicity was evaluated as maximum grade.

The evaluation of survival showed comparable outcome in LINAC and CK group in terms of overall survival (OS, p=0.15), local control (LC, p=0.62) & PFS (p=0.13). Two-year OS, LC & PFS was 100% vs 87%, 100% vs 100%, & 100% vs 87% for LINAC vs CK group, respectively.

Early gastrointestinal (GI) toxicity was comparable among the groups (G0 & G1 - 82% & 18% vs 68% & 26% for CK vs LINAC, respectively; p=0.22). Only 1 patient in LINAC arm had early GI G2 toxicity. Also, intermediate toxicity was comparable (p=0.44) - G0 & G1-84% & 8% vs 79% & 5% for CK vs LINAC, respectively. Two patients in LINAC arm had higher toxicity (G2 in 1 & G3 in 1 case). The difference between groups was statistically significant in terms of late GI toxicity–0 patients in CK arm, compared to 2 patients with G1 and 1 patient with G2 toxicity in LINAC group (p=0.02).

Early, intermediate and late genitourinary (GU) toxicity in both arms showed no statistical difference between the groups (p=0.19 for early, 0.23 for intermediate & 0.40 for late toxicity). Early GU G0, G1 & G2 was observed in 76%, 21% & 3% vs 63%, 21% & 16% for CK vs LINAC, respectively. Intermediate GU G0, G1 & G2 toxicity was-82%,10% & 0% vs 68%, 16% & 10% for CK vs LINAC, respectively. Late GU toxicity G1/G2 was observed in 2 patients in CK arm (2 cases of G1 toxicity) and in 2 cases in LINAC SBRT arm (1 G1 & 1 G2 toxicity).

Both SBRT techniques provides similar oncologic outcome of prostate cancer patients. On general, treatment toxicity was comparable with slightly higher late GI toxicity in LINAC arm. Longer follow-up and larger group is needed to better evaluate that differences.