Acute and Late Toxicity after Moderate Hypofractionation with Simultaneous Integrated Boost (SIB) Radiation Therapy for Prostate Cancer. A Single Institution, Prospective Study

Abstract

Asbtract To 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.

Secondary bladder and rectal cancer risk estimates following standard fractionated and moderately hypofractionated VMAT for prostate carcinoma

“…The dose constraints of bladder and rectum used for the generation of SF‐VMAT plans were taken from QUANTEC 17 whereas those applied for the HF‐VMAT 1 were derived from the RTOG‐0415 15 . The constraints of the femoral heads for the above treatment plans delivering 78 and 70 Gy to the tumor site were the same as those applied by Lawton et al 18 and Jorgo et al 19 , respectively. The HF‐VMAT 2 plans were carried out on the basis of previously published dosimetric constraints for the organs‐at‐risk 20 .…”

“… The quantity Vn denotes the % of the target and/or organ volume receiving a dose of n Gy. These constraints were taken from the literature 15–20 …”

“…These constraints were taken from the literature. [15][16][17][18][19][20] TABLE II. The model parameters used for estimating the organ equivalent dose and the excess absolute risk for developing secondary bladder or rectal malignancies as derived from the literature.…”

Moderately Hypofractionated Intensity Modulated Radiation Therapy With Simultaneous Integrated Boost for Prostate Cancer: Five-Year Toxicity Results From a Prospective Phase I/II Trial

“…While our rates of GU toxicities are comparable, our rate of GI toxicity is numerically lower and could be explained by larger PTV expansions or complete SV coverage in the Di Muzio trial. In addition, there have been other smaller trials confirming that SIB treatment of pelvic lymph nodes is safe, at various fraction sizes from 1.56 Gy to 2 Gy (total doses from 50 Gy to 56 Gy) with all trials showing acute grade 3 or higher GI toxicity <3% and late grade 3 or higher GI toxicity <10% (26,(30)(31)(32)(33)(34)(35)(36).…”

Comparative dosimetrical analysis of intensity-modulated arc therapy, CyberKnife therapy and image-guided interstitial HDR and LDR brachytherapy of low risk prostate cancer

“…CTV was extended using an isotropic 5 mm margin. The prescribed dose was 70 Gy, the dose of the daily fractions was 2.5 Gy for the PTV [22]. The protocol of our PROMOBRA study was applied for treatment planning in both HDR and LDR BT plans [23].…”