Risk-Adaptive Volumetric Modulated Arc Therapy Using Biological Objective Functions for Subvolume Boosting in Radiotherapy

Abstract

Objectives. Simultaneous integrated boost (SIB) for prostate cancer allows increases in tumor control probability while respecting normal tissue dose constraints. Biological optimization functions that optimize based on treatment outcome can be used to create SIB prostate plans. This study investigates the feasibility of biologically optimized volumetric modulated arc therapy (VMAT) for SIB prostate radiotherapy. Methods. Five prostate cancer patients with diffusion-weighted MR images were selected for analysis. A two-step VMAT optimization was performed, which consisted of an initial biological optimization of a static gantry angle delivery followed by conversion of the static delivery to a single arc VMAT plan. A dosimetric analysis was performed on the resulting plans. Results. The VMAT plans resulted in a ΔEUD between the prostate and the boost volume of between 15.1 Gy and 20.3 Gy. Rectal volumes receiving 75.6 Gy ranged from 4.5 to 9.9%. Expected rectal normal tissue complication probabilities were between 8.6% and 21.4%. Maximum bladder doses ranged from 73.6 Gy to 75.8 Gy. Estimated treatment time was 120 s or less. Conclusions. The presented biological optimization method resulted in deliverable VMAT plans that achieved sufficient modulation for SIB without violating rectal and bladder dose constraints. Advances in knowledge. This study presents a method for creating simultaneous integrated boost VMAT treatments using biological outcome objective functions.

The Potential Role of Magnetic Resonance Spectroscopy in Image-Guided Radiotherapy

“…The intra-prostatic GTV as outlined with 18 F Choline PET–CT, a cell proliferation marker with intense accumulation in prostatic cancer cell, was treated up to 90 Gy without exceeding the dose constraints to the bladder and rectum with the IMRT technique. Other dosimetric studies corroborated the feasibility of PET-based GTV dose escalation up to 100 Gy with IGRT for patients with prostate cancer ( 32 , 33 ). The potential of MRS for potential intra-prostatic GTV dose escalation with IMRT was highlighted in one dosimetric study where the prostate was treated to 70 Gy at 1.8 Gy/fraction while the GTV was treated to 90 Gy at 2.25 Gy ( 34 ).…”

Functional imaging-guided carbon ion irradiation with simultaneous integrated boost for localized prostate cancer: study protocol for a phase II randomized controlled clinical trial

“…Previously, we conducted a phase I/II dose-escalation CIRT study for localized prostate cancer, and the results showed that the irradiation dose of 65.6GyE/16 fractions to the whole prostate and seminal vesical was safe. Furthermore, dosimetric studies [ 26 , 27 ] and clinical data [ 28 , 29 ] proved that SIB irradiation had the advantage of improving the treatment efficacy for prostate cancer without increasing irradiation dose and toxicities of rectal and bladder. Therefore, we think it is reasonable to treat localized prostate cancer using SIB carbon ion radiotherapy technique, and this first randomized controlled trial of SIB carbon ion radiotherapy for localized prostate cancer is designed.…”

“…They found that SIB was a more effective method than homogeneous dose technique, significantly improving local control rate without increasing the normal tissue complications. Dosimetric studies [ 26 , 27 ] and clinical data [ 28 , 29 ] on volumetric modulated arc therapy (VMAT) and IMRT technologies further proved that SIB technique of prostate cancer may not increase the irradiation dose and toxic reactions of rectal and bladder, which indicated that simultaneous integrated boost irradiation had the advantage of improving the treatment efficacy without increasing the side effects for prostate cancer. Thus, patients might benefit from the SIB technique for solid tumors with improved tumor control and limited normal tissue damage.…”

Prostate Cancer Volumetric Arc Therapy (VMAT) Analysis

“…However, the dose escalation is limited by normal tissues toxicities where the rectum is subject to late toxicity after prostate cancer radiotherapy [10,11]. These findings were reiterated by Hardcastle et al [12] and showed that VMAT reduces dose to the rectum. Also, some reports have recommended that dose escalation in the order of 81 Gy or 70.2 Gy for prostate and prostate bed, respectively, will lead to a greater TCP suggesting a strong dose-effect relationship.…”