Abstract
AsbtractTo evaluate the acute and late toxicity using moderately hypofractionated, intensity-modulated radiotherapy (IMRT) with a simultaneous integrated boost (SIB) to prostate for patients with intermediate and high risk prostate cancer. From 2015 to 2017, 162 patients were treated with IMRT with SIB to the prostate. IMRT plans were designed to deliver 50.4Gy in 28 fractions (1.8 Gy/fraction) to the pelvic lymph nodes (whole pelvis radiotherapy, WPRT) while simultaneously delivering 57.4 Gy in 28 fractions (2.05 Gy/fraction) to the seminal vesicles and 70 Gy in 28 fractions (2.5 Gy/fraction) to the prostate for high risk patients. For intermediate risk patients the same technique was applied, without WPRT. Acute and cumulative late genitourinary (GU) and gastrointestinal (GI) toxicities were scored according to the Radiation Therapy Oncology Group (RTOG) scoring system. Of the 162 patients enrolled, 156 (96%) completed the treatment as planned. The median follow-up time was 30 months. Seventy-eight patients (48.2%) were treated with WPRT. The rate of acute grade ≥ 2 GI and GU toxicities in all patients were 22% and 58%, respectively. The rate of cumulative late grade ≥ 2 GI and GU toxicities were 11% and 17%, respectively. Acute grade 3 GI and GU toxicities occurred in 1% and 1%. Late grade 3 GI and GU side effects occurred in 5% and 4%, respectively. None of the patients developed grade ≥ 4 toxicity. IMRT with SIB technique using moderate hypofractionation to the prostate is feasible treatment option for intermediate and high risk patients, associated with low rate of severe GU and GI toxicities.
Highlights
Several randomized trials have shown improved biochemical control with dose escalation for prostate cancer [1,2,3]
The therapeutic outcome using external beam radiotherapy is expected to be improved with hypofractionation, in case of delivering higher biologically effective dose (BED) than with conventional external beam radiotherapy
IGRT was performed with fiducial markers, kV CBCT or MV CBCT in 32.7%, 61.1% and 6.2% of the patients, respectively.BStep and shoot^ intensity-modulated radiotherapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT) techniques were applied in 6.2% and 93.8% of patients, respectively
Summary
Several randomized trials have shown improved biochemical control with dose escalation for prostate cancer [1,2,3]. Asα/β ratio for rectum and urinary bladder is estimated to be 3Gy and 5-10Gy, respectively, the low α/β ratio ofprostate cancer theoretically allows dose escalation with hypofractionation without increasing late toxicity [6]. Beyond the advantages in terms of tumour control and late toxicity, the use of large dose per fraction is preferred by patients and may have important implications for costeffectiveness by shortening the overall treatment time. Several contemporary phase III, randomized trials with mature data have confirmed similar tumour control and late toxicity among various hypofractionated regimens to conventionally fractionated external beam radiotherapy [7]. Of the patients risk groups, except one trial, the treatment target volume was the prostate gland and ±
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