A comparative study of prostate PTV margins for patients using hydrogel spacer or rectal balloon in proton therapy

PurposeTo compare the planning target volume (PTV) margins needed for prostate patients who have used hydrogel spacer or rectal balloon during proton treatments.MethodTotal of 190 prostate patients treated with proton therapy during 2017 were selected for this study. Of these patients, 96 had hydrogel spacer injection and 94 patients had only rectal balloons insertion. All patients had implanted gold markers inside the prostate for daily target alignment. Post-treatment radigraphs were obtained to evaluate prostate intrafraction motion. The systematic and random components of patient setup residual error and prostate intrafraction motion error were obtained. PTV margins were calculated using the van Herk formula for both patient groups.ResultsFor setup residual error, the mean values in the superior-inferior (SI) direction and the variances in the left–right (LR) direction were statistically different between the two groups. For intrafraction motion, there were significant differences of the mean values in the SI direction and of the variances in both LR and anterior-posterior (AP) directions. The population PTV margins for hydrogel spacer group were 2.6 mm, 3.3 mm, and 1.6 mm in LR, SI, AP directions, respectively. For the rectal balloon group, the PTV margins were 2.1 mm, 3.1 mm, and 2.0 mm in LR, SI, AP directions, respectively.ConclusionStatistically significant differences were observed in the patient setup and prostate intrafraction motion errors of the two patient groups. However, under the current protocol of bladder preparation and daily marker-based x-ray image-guidance, population PTV margins were comparable between the two patient groups.     

Incorporation of tumor motion directionality in margin recipe: The directional MidP strategy

PurposePlanning target volume (PTV) definition based on Mid-Position (Mid-P) strategy typically integrates breathing motion from tumor positions variances along the conventional axes of the DICOM coordinate system. Tumor motion directionality is thus neglected even though it is one of its stable characteristics in time. We therefore propose the directional MidP approach (MidP dir), which allows motion directionality to be incorporated into PTV margins. A second objective consists in assessing the ability of the proposed method to better take care of respiratory motion uncertainty.Methods11 lung tumors from 10 patients with supra-centimetric motion were included. PTV were generated according to the MidP and MidP dir strategies starting from planning 4D CT.ResultsPTV_{MidP dir} volume didn’t differ from the PTV_MidP volume: 31351 mm³ IC95% [17242–45459] vs. 31003 mm³ IC95% [ 17347–44659], p = 0.477 respectively. PTV_{MidP dir} morphology was different and appeared more oblong along the main motion axis. The relative difference between 3D and 4D doses was on average 1.09%, p = 0.011 and 0.74%, p = 0.032 improved with directional MidP for D_99% and D_95%. D_2% was not significantly different between both approaches. The improvement in dosimetric coverage fluctuated substantially from one lesion to another and was all the more important as motion showed a large amplitude, some obliquity with respect to conventional axes and small hysteresis.ConclusionsDirectional MidP method allows tumor motion to be taken into account more tightly as a geometrical uncertainty without increasing the irradiation volume.     

Local control rates in stereotactic body radiotherapy (SBRT) of lung metastases associated with the biologically effective dose

AimTo evaluate dose differences in lung metastases treated with stereotactic body radiotherapy (SBRT), and the correlation with local control, regarding the dose algorithm, target volume and tissue density.BackgroundSeveral studies showed excellent local control rates in SBRT for lung metastases, with different fractionation schemes depending on the tumour location or size. These results depend on the dose distributions received by the lesions in terms of the tissue heterogeneity corrections performed by the dose algorithms.Materials and methodsForty-seven lung metastases treated with SBRT, using intrafraction control and respiratory gating with internal fiducial markers as surrogates (ExacTrac, BrainLAB AG), were calculated using Pencil Beam (PB) and Monte Carlo (MC) (iPlan, BrainLAB AG).Dose differences between both algorithms were obtained for the dose received by 99% (D_99%) and 50% (D_50%) of the planning treatment volume (PTV). The biologically effective dose delivered to 99% (BED_99%) and 50% (BED_50%) of the PTV were estimated from the MC results. Local control was evaluated after 24 months of median follow-up (range: 3–52 months).ResultsThe greatest variations (40.0% in ΔD_99% and 38.4% in ΔD_50%) were found for the lower volume and density cases. The BED_99% and BED_50% were strongly correlated with observed local control rates: 100% and 61.5% for BED_99% > 85 Gy and <85 Gy (p < 0.0001), respectively, and 100% and 58.3% for BED_50% > 100 Gy and <100 Gy (p < 0.0001), respectively.ConclusionsLung metastases treated with SBRT, with delivered BED_99% > 85 Gy and BED_50% > 100 Gy, present better local control rates than those treated with lower BED values (p = 0.001).     

Assessment of daily dose accumulation for robustly optimized intensity modulated proton therapy treatment of prostate cancer

PurposeTo implement a daily CBCT based dose accumulation technique in order to assess ideal robust optimization (RO) parameters for IMPT treatment of prostate cancer.MethodsTen prostate cancer patients previously treated with VMAT and having daily CBCT were included. First, RO-IMPT plans were created with ± 3 mm and ± 5 mm patient setup and ± 3% proton range uncertainties, respectively. Second, the planning CT (pCT) was deformably registered to the CBCT to create a synthetic CT (sCT). Both daily and weekly sampling strategies were employed to determine optimal dose accumulation frequency. Doses were recalculated on sCTs for both ± 3 mm/±3% and ± 5 mm/±3% uncertainties and were accumulated back to the pCT. Accumulated doses generated from ± 3 mm/±3% and ± 5 mm/±3% RO-IMPT plans were evaluated using the clinical dose volume constraints for CTV, bladder, and rectum.ResultsDaily accumulated dose based on both ± 3mm/±3% and ±5 mm/±3% uncertainties for RO-IMPT plans resulted in satisfactory CTV coverage (RO-IMPT_3mm/3% CTV_V95 = 99.01 ± 0.87% vs. RO-IMPT_5mm/3% CTV_V95 = 99.81 ± 0.2%, P = 0.002). However, the accumulated dose based on ± 3 mm/3% RO-IMPT plans consistently provided greater OAR sparing than ±5 mm/±3% RO-IMPT plans (RO-IMPT_3mm/3% rectum_V65Gy = 2.93 ± 2.39% vs. RO-IMPT_5mm/3% rectum_V65Gy = 4.38 ± 3%, P < 0.01; RO-IMPT_3mm/3% bladder_V65Gy = 5.2 ± 7.12% vs. RO-IMPT_5mm/3% bladder_V65Gy = 7.12 ± 9.59%, P < 0.01). The gamma analysis showed high dosimetric agreement between weekly and daily accumulated dose distributions.ConclusionsThis study demonstrated that for RO-IMPT optimization, ±3mm/±3% uncertainty is sufficient to create plans that meet desired CTV coverage while achieving superior sparing to OARs when compared with ± 5 mm/±3% uncertainty. Furthermore, weekly dose accumulation can accurately estimate the overall dose delivered to prostate cancer patients.     

3D image-based dosimetry for Yttrium-90 radioembolization of hepatocellular carcinoma: Impact of imaging method on absorbed dose estimates

BackgroundTo improve therapy outcome of Yttrium-90 selective internal radiation therapy (⁹⁰Y SIRT), patient-specific post-therapeutic dosimetry is required. For this purpose, various dosimetric approaches based on different available imaging data have been reported. The aim of this work was to compare post-therapeutic 3D absorbed dose images using Technetium-99m (^99mTc) MAA SPECT/CT, Yttrium-90 (⁹⁰Y) bremsstrahlung (BRS) SPECT/CT, and ⁹⁰Y PET/CT.MethodsTen SIRTs of nine patients with unresectable hepatocellular carcinoma (HCC) were investigated. The ^99mTc SPECT/CT data, obtained from ^99mTc-MAA-based treatment simulation prior to ⁹⁰Y SIRT, were scaled with the administered ⁹⁰Y therapy activity. 3D absorbed dose images were generated by dose kernel convolution with scaled ^99mTc/⁹⁰Y SPECT/CT, ⁹⁰Y BRS SPECT/CT, and ⁹⁰Y PET/CT data of each patient. Absorbed dose estimates in tumor and healthy liver tissue obtained using the two SPECT/CT methods were compared against ⁹⁰Y PET/CT.ResultsThe percentage deviation of tumor absorbed dose estimates from ⁹⁰Y PET/CT values was on average −2 ± 18% for scaled ^99mTc/⁹⁰Y SPECT/CT, whereas estimates from ⁹⁰Y BRS SPECT/CT differed on average by −50 ± 13%. For healthy liver absorbed dose estimates, all three imaging methods revealed comparable values.ConclusionThe quantification capabilities of the imaging data influence ⁹⁰Y SIRT tumor dosimetry, while healthy liver absorbed dose values were comparable for all investigated imaging data. When no ⁹⁰Y PET/CT image data are available, the proposed scaled ^99mTc/⁹⁰Y SPECT/CT dosimetry method was found to be more appropriate for HCC tumor dosimetry than ⁹⁰Y BRS SPECT/CT based dosimetry.     

Retrospective review of locally set tolerances for VMAT prostate patient specific QA using the COMPASS® system

PurposeThis study retrospectively reviewed locally set pass rates/tolerances for COMPASS^® pre-treatment quality assurance results for RapidArc prostate plans to determine if these are appropriate. This was performed via quantifying the agreement between treatment planning system calculations and measurements based on absolute dose comparisons (3% tolerance for all dose points) and global gamma index assessment (3%/3 mm criterion for 97% of points).MethodSeventy-three prostate one-arc RapidArc plans, delivered by four dosimetrically matched linacs, were measured using the MatriXX Evolution two-dimensional array and analysed using COMPASS^® (v.3, IBA Dosimetry). For the planning target volumes (PTV) considered, the D_99%, D_50%, D_1% and D_Mean differences were analysed. The percentage volume with gamma greater than 1, average gamma and D_Mean difference were investigated for all structures. Nine plans were also assessed across the linac fleet to investigate potential linac dependence of results.Results and ConclusionsRegarding PTV D_Mean differences, all plans fell within the 3% tolerance and mostly within 2%, although there was a relatively small systematic difference. The absolute percentage differences of average and median doses suggested a weak linac dependence of the results which was found to be clinically insignificant. New stricter tolerances were established both for dose comparisons and gamma evaluation. Correlation between the gamma pass rates and the differences in the D_99%, D_50% and D_1% was found to be moderate suggesting that gamma analysis in isolation has questionable clinical meaning and should only be used to indicate outliers for further analysis.     

Prognostic value of pre-infusion tumor growth rate for patients with lymphoma receiving chimeric antigen receptor T-cell therapy

Background aimsChimeric antigen receptor T-cell therapy (CART) prolongs survival for patients with refractory or relapsed lymphoma, yet its efficacy is affected by the tumor burden. The relevance of tumor kinetics before infusion is unknown. We aimed to study the prognostic value of the pre-infusion tumor growth rate (TGR^pre-BL) for progression-free (PFS) and overall survival (OS).MethodsConsecutive patients with available pre-baseline (pre-BL) and baseline (BL) computed tomography or positron emission tomography/computed tomography scan before CART were included. TGR was determined as change of Lugano criteria-based tumor burden between pre-BL, BL and follow-up examinations (FU) in relation to days between imaging exams. Overall response rate (ORR), depth or response (DoR) and PFS were determined based on Lugano criteria. Multivariate regression analysis studied association of TGR with ORR and DoR. Proportional Cox regression analysis studied association of TGR with PFS and OS.ResultsIn total, 62 patients met the inclusion criteria. The median TGR^pre-BL was 7.5 mm²/d (interquartile range –14.6 mm²/d to 48.7 mm²/d); TGR^pre-BL was positive (TGR^{pre-BL POS}) in 58% of patients and negative (TGR^{pre-BL NEG}, indicating tumor shrinkage) in 42% of patients. Patients who were TGR^{pre-BL POS} had a 90-day (FU2) ORR of 62%, a DoR of –86% and a median PFS of 124 days. Patients who were TGR^{pre-BL NEG} had a 90-day ORR of 44%, DoR of –47% and a median PFS of 105 days. ORR and DoR were not associated with slower TGR (P = 0.751, P = 0.198). Patients with an increase of TGR from pre-BL over BL to 30-day FU (FU1) ≥100% (TGR^{pre-BL-to-FU1≥100%}) showed a significant association with shorter median PFS (31 days versus 343 days, P = 0.002) and shorter median OS after CART (93 days versus not reached, P < 0.001), compared with patients with TGR^{pre-BL-to-FU1<100%}.ConclusionsIn the context of CART, differences in pre-infusion tumor kinetics showed minor differences in ORR, DoR, PFS and OS, whereas the change of the TGR from pre-BL to 30-day FU significantly stratified PFS and OS. In this patient population of refractory or relapsed lymphomas, TGR is readily available based on pre-BL imaging, and its change throughout CART should be explored as a potential novel imaging biomarker of early response.     

Evaluation of set-up errors in head and neck radiotherapy using electronic portal imaging

IntroductionThe aim of this study was to evaluate three-dimensional (3D) set-up errors and propose optimum margins for planning target volume (PTV) coverage in head and neck radiotherapy.MethodsThirty-five patients were included in the study. The total number of portal images studied was 632. Population systematic (Σ) and random (σ) errors for the patients with head and neck cancer were evaluated based on the portal images in the caudocranial longitudinal (CC) and left-right lateral (LR) direction measured in the anterior-posterior (AP) field, as well as from the images in the caudocranial longitudinal (CC) and dorsoventral lateral (DV) direction measured in the lateral (LAT) field. The values for the clinical-to-planning target volume (CTV-PTV) margins were calculated using ICRU Report 62 recommendations, along with Stroom's and van Herk's formulae.ResultsThe standard deviations of systematic set-up errors (Σ) ranged from 1.51 to 1.93 mm while the standard deviations of random set-up (σ) errors fell in between 1.77 and 1.86 mm. The mean 3D vector length of displacement was 2.66 mm. PTV margins calculated according to ICRU, Stroom's and van Herk's models were comprised between 1.95 and 6.16 mm in the three acquisition directions.Discussion and conclusionsBased on our results we can conclude that a 6-mm extension of CTV to PTV margin, as the lower limit, is enough to ensure that 90% of the patients treated for head and neck cancer will receive a minimum cumulative CTV dose greater than or equal to 95% of the prescribed dose.     

Comparison of 90Y SIRT predicted and delivered absorbed doses using a PSF conversion method

PurposeThe aims of this study were to develop and apply a method to correct for the differences in partial volume effects of pre-therapy Technetium-99 m (^99mTc)-MAA SPECT and post-therapy Yttrium-90 (⁹⁰Y) bremsstrahlung SPECT imaging in selective internal radiation therapy, and to use this method to improve quantitative comparison of predicted and delivered ⁹⁰Y absorbed doses.MethodsThe spatial resolution of ^99mTc SPECT data was converted to that of ⁹⁰Y SPECT data using a function calculated from ^99mTc and ⁹⁰Y point spread functions. This resolution conversion method (RCM) was first applied to ^99mTc and ⁹⁰Y SPECT phantom data to validate the method, and then to clinical data to assess the power of ^99mTc SPECT imaging to predict the therapeutic absorbed dose.ResultsThe maximum difference between absorbed doses to phantom spheres was 178%. This was reduced to 27% after the RCM was applied.The clinical data demonstrated differences within 38% for mean absorbed doses delivered to the normal liver, which were reduced to 20% after application of the RCM. Analysis of clinical data showed that therapeutic absorbed doses delivered to tumours greater than 100 cm³ were predicted to within 52%, although there were differences of up to 210% for smaller tumours, even after the RCM was applied.ConclusionsThe RCM was successfully verified using phantom data. Analysis of the clinical data established that the ^99mTc pre-therapy imaging was predictive of the ⁹⁰Y absorbed dose to the normal liver to within 20%, but had poor predictability for tumours smaller than 100 cm³.     

Utilization of cone-beam CT for offline evaluation of target volume coverage during prostate image-guided radiotherapy based on bony anatomy alignment

AimTo assess target volume coverage during prostate image-guided radiotherapy based on bony anatomy alignment and to assess possibility of safety margin reduction.BackgroundImplementation of IGRT should influence safety margins. Utilization of cone-beam CT provides current 3D anatomic information directly in irradiation position. Such information enables reconstruction of the actual dose distribution.Materials and methodsSeventeen prostate patients were treated with daily bony anatomy image-guidance. Cone-beam CT (CBCT) scans were acquired once a week immediately after bony anatomy alignment. After the prostate, seminal vesicles, rectum and bladder were contoured, the delivered dose distribution was reconstructed. Target dose coverage was evaluated by the proportion of the CTV encompassed by the 95% isodose. Original plans employed a 1 cm safety margin. Alternative plans assuming a smaller 7 mm margin between CTV and PTV were evaluated in the same way. Rectal and bladder volumes were compared with the initial ones. Rectal and bladder volumes irradiated with doses higher than 75 Gy, 70 Gy, 60 Gy, 50 Gy and 40 Gy were analyzed.ResultsIn 12% of reconstructed plans the prostate coverage was not sufficient. The prostate underdosage was observed in 5 patients. Coverage of seminal vesicles was not satisfactory in 3% of plans. Most of the target underdosage corresponded to excessive rectal or bladder filling. Evaluation of alternative plans assuming a smaller 7 mm margin revealed 22% and 11% of plans where prostate and seminal vesicles coverage, respectively, was compromised. These were distributed over 8 and 7 patients, respectively.ConclusionSufficient dose coverage of target volumes was not achieved for all patients. Reducing of safety margin is not acceptable. Initial rectal and bladder volumes cannot be considered representative for subsequent treatment.     

Estimation of optimal matching position for orthogonal kV setup images and minimal setup margins in radiotherapy of whole breast and lymph node areas

AimThe aim was to find an optimal setup image matching position and minimal setup margins to maximally spare the organs at risk in breast radiotherapy.BackgroundRadiotherapy of breast cancer is a routine task but has many challenges. We investigated residual position errors in whole breast radiotherapy when orthogonal setup images were matched to different bony landmarks.Materials and methodsA total of 1111 orthogonal setup image pairs and tangential field images were analyzed retrospectively for 50 consecutive patients. Residual errors in the treatment field images were determined by matching the orthogonal setup images to the vertebrae, sternum, ribs and their compromises. The most important region was the chest wall as it is crucial for the dose delivered to the heart and the ipsilateral lung. Inter-observer variation in online image matching was investigated.ResultsThe best general image matching position was the compromise of the vertebrae, ribs and sternum, while the worst position was the vertebrae alone (p ≤ 0.03). The setup margins required for the chest wall varied from 4.3 mm to 5.5 mm in the lung direction while in the superior–inferior (SI) direction the margins varied from 5.1 mm to 7.6 mm. The inter-observer variation increased the minimal margins by approximately 1 mm. The margin of the lymph node areas should be at least 4.8 mm.ConclusionsSetup margins can be reduced by proper selection of a matching position for the orthogonal setup images. To retain the minimal margins sufficient, systematic error of the chest wall should not exceed 4 mm in the tangential field image.     

Determination of optimal planning target volume margins in patients with gynecological cancer

PurposeTo define optimal planning target volume (PTV) margins for intensity modulated radiotherapy (IMRT) ± knee-heel support (KHS) in patients treated with adjuvant radiotherapy.MethodsComputed tomography (CT) scans ± KHS of 10 patients were taken before and at 3rd and 5th week of treatment, fused and compared with initial IMRT plans.ResultsA PTV margin of 15 mm in anteroposterior (AP) and superoinferior (SI) directions and 5 mm in lateral directions were found to be adequate without any difference between ± KHS except for the SI shifts in CTV-primary at the 3rd week. Five mm margin for iliac CTV was found to be inadequate in 10–20% of patients in SI directions however when 7 mm margin was given for iliac PTV, it was found to be adequate. For presacral CTV, it was found that the most striking shift of the target volume was in the direction of AP. KHS caused significantly less volume of rectum and bladder in the treated volume.ConclusionsPTV margin of 15 mm in SI and AP, and 5 mm in lateral directions for CTV-primary were found to be adequate. A minimum of 7 mm PTV margin should be given to iliac CTV. The remarkable shifting in presacral CTV was believed to be due to the unforeseen hip malposition of obese patients. The KHS seems not to provide additional beneficial effect in decreasing the shifts both in CTV-primary and lymphatic, however it may have a beneficial effect of decreasing the OAR volume in PTV margins.     

Optimisation of reconstruction,volumetry and dosimetry for 99mTc-SPECT and 90Y-PET images: Towards reliable dose-volume histograms for selective internal radiation therapy with 90Y-microspheres

PurposeIn Selective Internal Radiation Therapy (SIRT), ^99mTc-MAA SPECT images are commonly used to predict microspheres distribution but recent works used ⁹⁰Y-microspheres PET images. Nevertheless, evaluation of the predictive power of ^99mTc-MAA has been hampered by the lack of reliable comparisons between ^99mTc-SPECT and ⁹⁰Y-PET images. Our aim was to determine the “in situ” optimisation procedure in order to reliably compare ^99mTc-SPECT and ⁹⁰Y-PET images and achieve optimal personal dosimetry.MethodsWe acquired ^99mTc-SPECT/CT and ⁹⁰Y-PET/CT images of NEMA and Jaszczak phantoms. We found the best reconstruction parameters for quantification and for volume estimations. We determined adaptive threshold curves on the volumetric reconstruction. We copied the optimised volumes on the quantitative reconstruction, named here the “cross volumes” technique. Finally, we compared ^99mTc-SPECT and ⁹⁰Y-PET Dose Volume Histograms.ResultsOur “in situ” optimisation procedure decreased errors on volumes and quantification (from −44.2% and −15.8% to −3.4% and −3.28%, respectively, for the 26.5 mL PET phantom sphere). Moreover, ^99mTc-SPECT and ⁹⁰Y-PET DVHs were equivalent only after the optimisation procedure (difference in mean dose <5% for the three biggest spheres).ConclusionsThis work showed that a preliminary “in situ” phantom study was necessary to optimise volumes and quantification of ^99mTc-SPECT and ⁹⁰Y-PET images and allowed to achieve a reliable comparison between patient treatment planning and post implant dosimetry, notably by the use of the “cross volumes” technique. Methodology developed in this work will enable robust evaluations of the predictive power of ^99mTc-SPECT, as well as dose-response relationship and side effects in SIRT treatments.     

Actividad antifúngica de los enjuagues bucales frente a Candida albicans y Rhodotorula mucilaginosa: un estudio in vitro

BackgroundCandida albicans and Rhodotorula mucilaginosa are yeasts of clinical importance in the oral cavity. In immunocompromised patients they can cause some pathologies that must be controlled with antimicrobials.AimsTo evaluate and compare the antimicrobial efficacy of commercially available mouthrinses against strains of C. albicans and R. mucilaginosa.MethodsThe six mouthwashes studied in vitro were formulated (alone or in combination) with chlorhexidine (CHX) 0.12%, CHX 0.1%, CHX 0.05%, cetylpyridinium chloride (CPC) 0.075%, CPC 0.05%, and essential oils. Ten C. albicans and R. mucilaginosa isolates each were studied. The agar diffusion method (Mueller Hinton II), with incubation at 32 °C was used to evaluate the antifungal activity.ResultsThe results of this study indicate that mouthwashes with CHX 0.1%, CHX 0.12%, CHX 0.05% + CPC 0.05%, CHX 0.12% + CPC 0.05% and CPC 0.075% have an antifungal effect against C. albicans and R. mucilaginosa. CHX 0.1% led to the broadest inhibition zone for C. albicans and R. mucilaginosa (25.65 ± 2.39 mm and 40.05 ± 3.31 mm). Essential oils did not show any antifungal activity. Statistical analysis showed no statistical difference between mouth rinses CHX 0.1%, CHX 0.12% and CHX 0.12% + CPC 0.05% (p = 0.0001) against C. albicans and R. mucilaginosa.ConclusionsMouthwashes with CHX showed higher antifungal activity against C. albicans and R. mucilaginosa than other mouthwashes studied.     

Finding safe dose-volume constraints for re-irradiation with SBRT of patients with prostate cancer relapse: The IEO experience

AimThe primary aim of this study is to provide preliminary indications for safe constraints of rectum and bladder in patients re-irradiated with stereotactic body RT (SBRT).MethodsData from patients treated for prostate cancer (PCa) and intraprostatic relapse, from 1998 to 2016, were retrospectively collected. First RT course was delivered with 3D conformal RT techniques, SBRT or volumetric modulated arc therapy (VMAT). All patients underwent re-irradiation with SBRT with heavy hypofractionated schedules. Cumulative dose-volume values to organs at risk (OARs) were computed and possible correlation with developed toxicities was investigated.ResultsTwenty-six patients were included. Median age at re-irradiation was 75 years, mean interval between the two RT courses was 5.6 years and the median follow-up was 47.7 months (13.4–114.3 months). After re-irradiation, acute and late G ≥ 2 GU toxicity events were reported in 3 (12%) and 10 (38%) patients, respectively, while late G ≥ 2 GI events were reported in 4 (15%) patients. No acute G ≥ 2 GI side effects were registered. Patients receiving an equivalent uniform dose of the two RT treatments < 131 Gy appeared to be at higher risk of progression (4-yr b-PFS: 19% vs 33%, p = 0.145). Cumulative re-irradiation constraints that appear to be safe are D_30% < 57.9 Gy for bladder and D_30% < 66.0 Gy, D_60% < 38.0 Gy and V_{122.1 Gy} < 5% for rectum.ConclusionPreliminary re-irradiation constraints for bladder and rectum have been reported. Our preliminary investigation may serve to clear some grey areas of PCa re-irradiation.     

Validation of a method for “dose of the day” calculation in head-neck tomotherapy by using planning ct-to-MVCT deformable image registration

PurposeThe aim of this study was to test the feasibility and dosimetric accuracy of a method that employs planning CT-to-MVCT deformable image registration (DIR) for calculation of the daily dose for head and neck (HN) patients treated with Helical Tomotherapy (HT).MethodsFor each patient, the planning kVCT (CTplan) was deformably registered to the MVCT acquired at the 15th therapy session (MV15) with a B-Spline Free Form algorithm using Mattes mutual information (open-source software 3D Slicer), resulting in a deformed CT (CTdef). On the same day as MVCT15, a kVCT was acquired with the patient in the same treatment position (CT15). The original HT plans were recalculated both on CTdef and CT15, and the corresponding dose distributions were compared; local dose differences <2% of the prescribed dose (DD2%) and 2D/3D gamma-index values (2%-2 mm) were assessed respectively with Mapcheck SNC Patient software (Sun Nuclear) and with 3D-Slicer.ResultsOn average, 87.9% ± 1.2% of voxels were found for DD2% (on average 27 slices available for each patient) and 94.6% ± 0.8% of points passed the 2D gamma analysis test while the 3D gamma test was satisfied in 94.8% ± 0.8% of body’s voxels.ConclusionsThis study represents the first demonstration of the dosimetric accuracy of kVCT-to-MVCT DIR for dose of the day computations. The suggested method is sufficiently fast and reliable to be used for daily delivered dose evaluations in clinical strategies for adaptive Tomotherapy of HN cancer.     

Respiratory motion of adrenal gland metastases: Analyses using four-dimensional computed tomography images

PurposeTo evaluate the respiratory motion of adrenal gland metastases in three-dimensional directions using four-dimensional computed tomography (4DCT) images.MethodsFrom January 2013 to May 2016, 12 patients with adrenal gland metastases were included in this study. They all underwent 4DCT scans to assess respiratory motion of adrenal gland metastases in free breathing state. The 4DCT images were sorted into 10 image series according to the respiratory phase from the end inspiration to the end expiration, and then transferred to FocalSim workstation. All gross tumor volumes (GTVs) of adrenal gland metastases were drawn by a single physician and confirmed by a second. Relative coordinates of adrenal gland metastases were automatically generated to calculate adrenal gland metastases motion in different axial directions.ResultsThe average respiratory motion of adrenal gland metastases in left-right (LR), cranial-caudal (CC), anterior-posterior (AP), 3-dimensional (3D) vector directions was 3.4 ± 2.2 mm, 9.5 ± 5.5 mm, 3.8 ± 2.0 mm and 11.3 ± 5.3 mm, respectively. The ratios were 58.6% ± 11.4% and 63.2% ± 12.5% when the volumes of GTV_In0% and GTV _In100% were compared with volume of IGTV_10phase. The volume ratio of IGTV_10phase to GTV_3D was 1.73 ± 0.48.ConclusionsAdrenal gland metastasis is a respiration-induced moving target, and an internal target volume boundary should be provided when designing the treatment plan. The CC motion of adrenal gland metastasis is predominant and >5 mm, thus motion management strategies are recommended for patients undergoing external radiotherapy for adrenal gland metastasis.