Evaluation of a commercial biologically based IMRT treatment planning system

Abstract

A new inverse treatment planning system (TPS) for external beam radiation therapy with high energy photons is commercially available that utilizes both dose-volume-based cost functions and a selection of cost functions which are based on biological models. The purpose of this work is to evaluate quality of intensity-modulated radiation therapy (IMRT) plans resulting from the use of biological cost functions in comparison to plans designed using a traditional TPS employing dose-volume-based optimization. Treatment planning was performed independently at two institutions. For six cancer patients, including head and neck (one case from each institution), prostate, brain, liver, and rectal cases, segmental multileaf collimator IMRT plans were designed using biological cost functions and compared with clinically used dose-based plans for the same patients. Dose-volume histograms and dosimetric indices, such as minimum, maximum, and mean dose, were extracted and compared between the two types of treatment plans. Comparisons of the generalized equivalent uniform dose (EUD), a previously proposed plan quality index (fEUD), target conformity and heterogeneity indices, and the number of segments and monitor units were also performed. The most prominent feature of the biologically based plans was better sparing of organs at risk (OARs). When all plans from both institutions were combined, the biologically based plans resulted in smaller EUD values for 26 out of 33 OARs by an average of 5.6 Gy (range 0.24 to 15 Gy). Owing to more efficient beam segmentation and leaf sequencing tools implemented in the biologically based TPS compared to the dose-based TPS, an estimated treatment delivery time was shorter in most (five out of six) cases with some plans showing up to 50% reduction. The biologically based plans were generally characterized by a smaller conformity index, but greater heterogeneity index compared to the dose-based plans. Overall, compared to plans based on dose-volume optimization, plans with equivalent target coverage obtained using the biologically based TPS demonstrate improved dose distributions for the majority of normal structures.

Monte Carlo-Based Dose Calculation in Postprostatectomy Image-Guided Intensity Modulated Radiotherapy: A Pilot Study

“…A study conducted by Qi et al [5] concluded that "the use of biological models in treatment planning optimization can generate IMRT plans with significantly improved normal tissue sparing with similar or slightly increased dose heterogeneity in the target." Considering the improvements in OAR doses using Monaco's biological cost functions, confirmed both in this study and in an independent evaluation by Semenenko et al [8], there may be scope in the future to dose escalate PPRT since both five-year biochemical relapse-free survival and disease-free survival were significantly higher (83% versus 71% ( = 0.001) and 94% versus 88% ( = 0.005), resp.) in a cohort of patients who received 70 Gy [9].…”

Imrt in Image-Guided Single Vocal Cord Irradiation

“…In our clinic, some of the IMRT beams from the presented plans were verified using a two-dimensional detector array (15). Gamma analyses showed good agreement between the dose distributions calculated using the Monaco TPS and the measured distributions.…”

“…In the Monaco TPS, the plans were configured using biological and physical constraints (13)(14)(15). For the PTV, a Poisson cell kill model was used combined with a quadratic overdose constraint to avoid hot spots inside the PTV.…”

A quality control method for intensity‐modulated radiation therapy planning based on generalized equivalent uniform dose

“…Several treatment planning systems have been developed that incorporate gEUD cost functions for IMRT optimization. Previous investigations have confirmed the effectiveness of gEUD cost functions for plan optimization 6, 7, 8. For more complex plans, more iterations are required because many parameters need to be finely tuned for dose–volume (DV)‐based objective functions.…”