[Five-year results of IMRT for prostate cancer - tumor control]

Abstract

Background: Intensity-modulated radiation therapy (IMRT) is the method of choice in external-beam radiotherapy tolocalized prostate cancer. This work analyses five year results of IMRT with a dose of 78/82 Gy.

Patients and methods: From June 2003 to December 2007, the IMRT technique was employed to treat 233 patients with T1-3 N0 M0 prostate cancer. It was supplemented by hormone therapy especially in high-risk patients. Two IMRT techniques were applied - IMRT with a dose of 78 Gy in 39 fractions to prostate and seminal vesicles (SV) (IMRT 78) and IMRT with simultaneous integrated 82 Gy boost to prostate concurrently with 73,8 Gy in 41 fractions to SV (IMRT SIB 82). The IMRT 78 technique was used in 160 patients (69%). Seventy-three (31%) patients with intermediate (IR) or high-risk (HR) prostate cancer without SV involvement were treated with IMRT SIB 82 technique. The PSA relapse was defined as an increase in PSA of at least 2.0 ng/mL above the nadir or in comparison to the value at the initiation of hormone therapy. Clinical relapse was defined as an occurence of distant metastases and/or local recurrence.

Results: The median follow-up of our patients´ population was 4.3 years (range 0.6-8.9 years). The estimated 5-year PSA relapse-free survival in low-risk (LR), IR and HR patients was 86%, 89% and 83%, respectively (p = NS). In a multivariate analysis, Gleason score (GS) 8-10 was associated with significantly higher risk of PSA relapse (RR 2.76), while higher age at the time of diagnosis significantly decreased the PSA relapse risk (RR 0.94). The estimated 5-year clinical relapse-free survival in LR, IR and HR patients was 100%, 99% and 95%, respectively (p = NS). In a univariate analysis, both GS and PSA had a significant impact on the 5-year clinical relapse-free survival - GS 2-7 97 % vs GS 8-10 88 % (p = 0.03), PSA 20 98 % vs PSA > 20 85 % (p < 0.01).

Conclusion: Treatment of localized prostate cancer using IMRT with a dose 78/82 Gy yielded an excellent 5-year tumour control with a risk of clinical relapse being less than 5%.