Abstract
ObjectiveDosimetric comparison of HIPO (hybrid inverse planning optimisation) and IPSA (inverse planning simulated annealing) inverse and forward optimisation (FO) methods in brachytherapy (BT) of breast, cervical and prostate cancer.MethodsAt our institute 38 breast, 47 cervical and 50 prostate cancer patients treated with image-guided interstitial high-dose-rate BT were selected. Treatment plans were created using HIPO and IPSA inverse optimisation methods as well as FO. The dose–volume parameters of different treatment plans were compared with Friedman ANOVA and the LSD post-hoc test.ResultsIPSA creates less dose coverage to the target volume than HIPO or FO: V100 was 91.7%, 91% and 91.9% for HIPO, IPSA and FO plans (p = 0.1784) in breast BT; 90.4%, 89.2% and 91% (p = 0.0045) in cervical BT; and 97.1%, 96.2% and 97.7% (p = 0.0005) in prostate BT, respectively. HIPO results in more conformal plans: COIN was 0.72, 0.71 and 0.69 (p = 0.0306) in breast BT; 0.6, 0.47 and 0.58 (p < 0.001) in cervical BT; and 0.8, 0.7 and 0.7 (p < 0.001) in prostate BT, respectively. In breast BT, dose to the skin and lung was smaller with HIPO and FO than with IPSA. In cervical BT, dose to the rectum, sigmoid and bowel was larger using IPSA than with HIPO or FO. In prostate BT, dose to the urethra was higher and the rectal dose was smaller using FO than with inverse methods.ConclusionIn interstitial breast and prostate BT, HIPO results in comparable dose–volume parameters to FO, but HIPO plans are more conformal. In cervical BT, HIPO produces dosimetrically acceptable plans only when more needles are used. The dosimetric quality of IPSA plans is suboptimal and results in unnecessary larger active lengths.
Highlights
In spite of some early publications on inverse optimisation in brachytherapy (BT) [1, 2], inverse dose planning has played a significant role in external beam radiotherapy (EBRT) treatment planning since 2000 [3]
Automatic skin contouring is appropriate for forward optimisation (FO) in interstitial breast BT, but a special 5 mm thick skin shell is needed for inverse methods
The dose–volume parameters do not follow the Gaussian distribution (F-tests were significant for all parameters), so the studied parameters of different treatment plans were compared with non-parametric Friedman ANOVA and the LSD post-hoc test (Statistica 12.3, StatSoft, Tulsa, OK, USA). Both Hybrid inverse planning optimisation (HIPO) and Inverse planning simulated annealing (IPSA) methods decrease the time of planning process to FO, from 25 to 15 min in breast BT, from 10 to 7 min in cervical BT and from 20 to 10 min on average in prostate BT
Summary
In spite of some early publications on inverse optimisation in brachytherapy (BT) [1, 2], inverse dose planning has played a significant role in external beam radiotherapy (EBRT) treatment planning since 2000 [3]. In brachytherapy these methods have become widespread in the past decade [4]. Beside the reproducibility of the plans, their practical advantage is reduced planning time It needs the accurate setup of the initial preset and it is beneficial only if sufficient degrees of freedom are available for the algorithm. Comprehensive dosimetric evaluation and comparison with the forward method are still awaited
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