This retrospective study aimed to report clinical outcomes of high-dose rate brachytherapy (HDR-BT) and whole pelvic radiation therapy (WPRT) in intermediate- to high-risk localised prostate cancer and to gain a better understanding of how behavioural variability of patients from various ethnic origins affects clinical practice.

In total, 116 localised intermediate- to high-risk prostate cancer patients who were treated during 2004–12 were enroled into the study. WPRT was delivered to the full pelvis (50 Gy per conventional fractionation) and two fractions (15 Gy per fraction) of high-dose rate brachytherapy were designed for all patients to the peripheral zone of McNeal. The reported results were biochemical control rate, toxicity profiles and behavioural variations of patients.

The median follow-up time was 51 months. The 4-year biochemical control rates, according to the American Society for Therapeutic Radiology and Oncology was 93·1%. T stage was the prognostic factor for biochemical control. No significant differences in biochemical control could be identified across ethnic groups (p>0·05). Five patients developed grade 3–4 gastrointestinal toxicity. Prior knowledge was commonly found among Caucasian patients and urinary functions seemed to be more concerned among Caucasian and Middle East patients than those from other ethnic origins.

Clinical outcomes of intermediate- to high-risk prostate cancer patients from various ethnic origins were comparable with that of the Caucasian-only population reported previously. A number of detected ethnic-related factors might be beneficial for treatment decision-making for patients with different cultural background and could be utilised to better personalise/optimise cancer care and aftercare.

To investigate the use of co-registration of the computerised tomography (CT) planning scan with transperineal ultrasound (TPUS) as an aid to the delineation of the clinical target volume (CTV), and the use of TPUS as a tool for inter- and intra-fractional monitoring in men with bilateral hip prostheses (b-P) undergoing prostate radiotherapy.

We marked the CTV of three patients with and without the co-registered TPUS images. A metal artefact reduction algorithm was utilised. Two patients were treated with intensity-modulated radiotherapy (IMRT) and one with volumetric-modulated arc therapy (VMAT). The inter- and intra-fractional monitoring details were reviewed retrospectively.

Clinician marking with TPUS/CT fusion improved the confidence of prostate CTV delineation leading to a consistent change in volumes across two observers. Inter- and intra-fractional monitoring was possible using TPUS as image guidance, as it is for those patients with non-prosthetic hips.

Using TPUS in the radiotherapy workflow has enabled us to more confidently plan, treat and monitor patients with b-HP. Due to transperineal image acquisition, the ultrasound images are not affected by the presence of hip prostheses, which are outside the field of view.

Current literature suggests the information and support needs of oncology patients undergoing radical radiotherapy to the prostate often remain unmet and can impact quality of life. We aimed to explore the effectiveness of delivery and opportunities for service improvement, including a group-based treatment review.

A total of 60 prostate patients completing radical radiotherapy (mean age 70, range 47–79) in a UK cancer-centre completed a self-designed questionnaire assessing information and support. To explore views on a group-based treatment review, 11% took part in a semi-structured interview. Descriptive data were computed and interviews transcribed and analysed thematically.

In all, 87% were satisfied with information and support when delivered by radiographers. However, 26% were only ‘sometimes’ able to complete bladder-filling, suggesting information regarding treatment delays would improve this. In total, 49% preferred both Doctor and Urology nurse reviews whereas 26% preferred nurse only; 70% stated their ‘concerns were always addressed’ by a nurse and 49% by a Doctor. Interviews revealed that a group review was generally acceptable with peer support an influencing factor.

Overall patients felt their needs were being met. Suggestions for improvement (more information on preparation, side effects and delays) will be implemented locally. Future work will explore the feasibility of group reviews in patients undergoing radical radiotherapy to the prostate.

Radiation therapy (RT) remains a common and effective treatment modality for patients with locally advanced prostate cancer. Technological advancements over the past decade have resulted in the introduction of intensity-modulated radiation therapy (IMRT) planning and delivery techniques that maximise the dose of radiation delivered to the prostate while sparing organs at risk (OAR). A more recent and evolving IMRT technique, called volumetric-modulated arc therapy (VMAT), involves a continuous irradiation at a constant or variable dose rate when the gantry rotates around the prostate using one or more arcs.

This paper reports on a dosimetric evaluation of our implementation of VMAT technique for prostate cancer treatment. A retrospective analysis of VMAT plans was performed for 300 prostate cancer patients treated during the period of January 2013 to December 2014. Two prescription cohorts of patients treated to a dose of 78 Gy in 39 fractions as the primary radiation therapy treatment (XRT) and 66 Gy in 33 fractions as a post-op or salvage XRT were considered.

The mean and maximal doses, dose inhomogeneities and conformity indexes for the planning target volumes were evaluated for each prescription cohort of patients. Similarly, the doses to OAR such as rectum, bladder and femoral heads were also assessed for various dose levels.

This study shows that highly conformal radiation dose distribution for the treatment of prostate cancer is achievable with the VMAT technique. It provides evidence to support the adoption of such conformal technology in many disease sites such as the prostate. We believe that our experience reported here could help form the foundation for individual institutions to evaluate and develop the most suitable planning criteria tailored to their own needs and priority. This endeavour hopefully will provide further improvement in the planning process and, therefore, help achieve an effective and efficient delivery of radiotherapy for prostate cancer.

The aim of this study is to develop predictive models to predict organ at risk (OAR) complication level, classification of OAR dose-volume and combination of this function with our in-house developed treatment decision support system.

We analysed the support vector machine and decision tree algorithm for predicting OAR complication level and toxicity in order to integrate this function into our in-house radiation treatment planning decision support system. A total of 12 TomoTherapyTM treatment plans for prostate cancer were established, and a hundred modelled plans were generated to analyse the toxicity prediction for bladder and rectum.

The toxicity prediction algorithm analysis showed 91·0% accuracy in the training process. A scatter plot for bladder and rectum was obtained by 100 modelled plans and classification result derived. OAR complication level was analysed and risk factor for 25% bladder and 50% rectum was detected by decision tree. Therefore, it was shown that complication prediction of patients using big data-based clinical information is possible.

We verified the accuracy of the tested algorithm using prostate cancer cases. Side effects can be minimised by applying this predictive modelling algorithm with the planning decision support system for patient-specific radiotherapy planning.

Late adverse effects following radiation therapy for prostate cancer involve the urinary and lower gastrointestinal tracts, with continuous rectal bleeding being the most serious issue. We focused on late adverse effects, particularly rectal bleeding after volumetric-modulated arc therapy (VMAT), for patients with locally advanced prostate cancer.

Seventy-three patients with localized prostate cancer were treated with radiation therapy using VMAT with an image-guided radiation therapy system. Patient age at the start of irradiation ranged from 54 to 81 years (median, 71 years). The follow-up period ranged from 23 to 87 months (median, 57 months). The prescribed total irradiation dose was 76 Gy in 38 fractions.

Late rectal bleeding was observed in 14 (19%) patients, with nine (12.3%), four (5.5%), and one (1.4%) being classified as grades 1, 2, and 3, respectively. One grade 3 patient with rectal bleeding had severe diabetes and was administered intravenous warfarin for cardiomyopathy.

VMAT may provide better accuracy and involve fewer time constraints for patients compared with other intensity-modulated radiation therapy (IMRT) methods. The incidence of late rectal bleeding in VMAT is almost equivalent to that of other IMRT methods.

Pelvic internal organs change in volume and position during radiotherapy. This may compromise the efficacy of treatment or worsen its toxicity. There may be limitations to fully correcting these changes using online image guidance; therefore, effective and consistent patient preparation and positioning remain important. This review aims to provide an overview of the extent of pelvic organ motion and strategies to manage this motion.

Given the breadth of this topic, a systematic review was not undertaken. Instead, existing systematic reviews and individual high-quality studies addressing strategies to manage pelvic organ motion have been discussed. Suggested levels of evidence and grades of recommendation for each strategy have been applied.

Various strategies to manage rectal changes have been investigated including diet and laxatives, enemas and rectal emptying tubes and rectal displacement with endorectal balloons (ERBs) and rectal spacers. Bladder-filling protocols and bladder ultrasound have been used to try to standardise bladder volume. Positioning the patient supine, using a full bladder and positioning prone with or without a belly board, has been examined in an attempt to reduce the volume of irradiated small bowel. Some randomised trials have been performed, with evidence to support the use of ERBs, rectal spacers, bladder-filling protocols and the supine over prone position in prostate radiotherapy. However, there was a lack of consistent high-quality evidence that would be applicable to different disease sites within the pelvis. Many studies included small numbers of patients were non-randomised, used less conformal radiotherapy techniques or did not report clinical outcomes such as toxicity.

There is uncertainty as to the clinical benefit of many of the commonly adopted interventions to minimise pelvic organ motion. Given this and the limitations in online image guidance compensation, further investigation of adaptive radiotherapy strategies is required.

To quantify the relationship between the planning target volume (PTV) dose homogeneity and organs at risk (OARs) sparing in correlation with anatomical parameters in prostate intensity-modulated radiotherapy (IMRT).

Nine IMRT plans with various target dose constraints’ priorities were created for 15 prostate cancer patients. Selected PTV and OARs parameters were calculated for the patients. A trade-off was assessed between homogeneity index (HI) and OAR sparing. Several anatomical parameters were evaluated to investigate their effects on the OAR sparing and HI.

Inverse exponential relationships were found between the OAR sparing and HI (average R2 of 0·983 and 0·994 for bladder and rectum, respectively). Decreasing the priority led to more OARs sparing (normal tissue complication probability reduction: 97·6 and 74·5%; mean dose reduction: 16·3 and 11·3% for bladder and rectum, respectively) and worsening of the HI (0·095–0·322) but with no significant effect on tumour control probability. Furthermore, OARs volumes, distances between OARs and PTV and their joint volumes had stronger correlations with OARs’ mean doses.

Enforcement of target dose constraints was more effective on the improvement of HIs for the patients with initial high HI values at low dose constraints’ priorities. Reducing the priority had more effects on the OARs sparing compared to HI, especially for the patients with high OAR doses in high priority plans. This can be attributed to smaller distances or greater joint volumes between the OARs and PTV.

Radiotherapy is one of the treatments used to treat prostate cancer, and dose escalation to 74–78 Gy in conventional fractionation is the standard regimen. Currently, according to the hypothesis of low alpha/beta ratio in prostate cancer cells, using hypo-fractionation has been reported in many publications with promising results. This retrospective study was designed to evaluate the implementation of a moderate hypo-fractionation regimen in high-risk prostate cancer in our division.

Between 2012 and 2017, 40 patients with high-risk, localised prostate cancer were treated by a moderate hypo-fractionation regimen (70 Gy at 2·5 Gy per fraction) with intensity-modulated radiation therapy. The data related to treatment outcomes and toxicities were evaluated.

The mean PSA at diagnosis was 86·2 ng/mL (95% CI 49·9–122·4). Thirty-eight patients received long-term hormonal therapy. Fifty-two percent had a Gleason score of 8–10, and 65% had an initial PSA >20 ng/mL. The mean doses (in EQD2) to the D50% of PTV, D2% of organs at risk (bladder, rectum and bowels) were 80, 78·3, 76·4, and 50·2 Gy, respectively. Two patients had biochemical recurrence during the follow-up period.

A moderate hypo-fractionation regimen (70 Gy at 2·5 Gy per fraction) is feasible. Our experience found that this regimen yields tolerable, acceptable toxicity profiles in high-risk, localised prostate cancer patients.

Standard external beam radiotherapy is a treatment option for patients with localised prostate cancer and is used in patients with low-, intermediate- and high-risk disease with androgen deprivation according to the risk of the disease. In the last few years, hypofractionated radiotherapy has been demonstrated to be as safe as standard radiotherapy if given over a shorter time than standard radiotherapy with larger doses per fraction. External radiotherapy for localised prostate cancer typically delivers 37–42 fractions of 1·8–2·0 Gy per fraction given 5 days per week over 7·5–8·5 weeks. Hypofractionated radiotherapy delivers 20–28 fractions of 2·5–2·6 Gy per fraction given 5 days per week over 4–5·6 weeks.

A retrospective analysis of assessment of 30 patients was undertaken from 2016 to 2018. The aim of this study was to evaluate the 2-year outcomes of 30 patients with prostate cancer treated with hypofractionated radiotherapy 70 Gy in 28 fractions.

Biochemical failure with hypofractionated radiotherapy was found in a total of 20% of patients. In the classification by risk groups, there were no biochemical failures in low-risk patients; in the low intermediate course, 3·3% of patients; in the high intermediate group, 3·3% patients; and in the high-risk group, the largest documented biochemical failure was in 13·3% of patients. For acute urinary toxicity, grade I was 56·6%; grade II, 6·6%. For acute rectal toxicity, grade I was 46·6%; grade II, 3·3%.

This is one of the first studies of hypofractionated radiotherapy in prostate cancer in Latin America, and the results of this study demonstrated that the outcomes were similar to the standard regimen in all risk groups.

The aim of this study was to evaluate whether RapidPlan (RP) could generate clinically acceptable prostate volumetric modulated arc therapy (VMAT) plans.

The in-house RP model was used to generate VMAT plans for 50 previously treated prostate cancer patients, with no additional optimisation being performed. The VMAT plans that were generated using the RP model were compared with the patients’ previous, manually optimised clinical plans (MP), none of which had been used for the development of the in-house RP prostate model. Differences between RP and MP in planning target volume (PTV) doses, organs at risk (OAR) sparing, monitor units (MU) and planning time required to produce treatment plans were analysed. Assessment of PTV doses was based on the conformation number (CN), homogeneity index (HI), D2%, D99% and the mean dose of the PTV. The OAR doses evaluated were the rectal V50 Gy, V65 Gy, V70 Gy and the mean dose, the bladder V65 Gy, V70 Gy and the mean dose, and the mean dose to both femurs.

D99% and mean dose of the PTV were lower for RP than for MP (p = 0·006 and p = 0·040, respectively).V50 Gy, V65 Gy and the mean dose to rectum were lower in RP than in MP (p < 0·001). V65 Gy, V70 Gy and the mean dose to bladder were lower in RP than in MP (p < 0·001). RP had enhanced the sparing of both femurs (p < 0·001) and significantly reduced the planning time to less than 5% of the time taken with MP. MU in RP was significantly higher than MP by an average of 52·5 MU (p < 0·001) and 46 out of the 50 RP plans were approved by the radiation oncologist.

This study has demonstrated that VMAT plans generated using an in-house RP prostate model in a single optimisation for prostate patients were clinically acceptable with comparable or better plan quality compared to MP. RP can add value and improve treatment planning efficiency in a high-throughput radiotherapy department through reduced plan optimisation time while maintaining consistency in the plan quality.

Magnetic resonance imaging (MRI) is indispensable for treatment planning in prostate radiotherapy (PR). Registration of MRI when compared to planning CT (pCT) is prone to uncertainty and this is rarely reported. In this study, we have compared three different types of registration methods to justify the direct use of MRI in PR.

Thirty patients treated for PR were retrospectively selected for this study and all underwent both CT and MRI. The MR scans were registered to the pCT using markers, focused and unfocussed methods and their registration are REGM, REGF, and REGNF, respectively. Registration comparison is done using the translational differences of three axes from the centre-of-mass values of gross tumour volume (GTV) generated using MRI.

The average difference in all three axes (x, y, z) is (1, 2·5, 2·3 mm) and (1, 3, 2·3 mm) for REGF-REFNF and REGF-REGM, respectively. MR-based GTV Volume is less in comparison to CT-based GTV and it is significantly different (p < 0·001).

Image registration uncertainty is unavoidable for a regular CT–MR workflow. Additional planning target volume margin ranging from 2 to 3mm could be avoided if MR-only workflow is employed. This reduction in the margin is beneficial for small tumours treated with hypofractionation.

The aim of this study is to compare three-dimensional conformal radiotherapy (3D-CRT), intensity-modulated radiotherapy (IMRT) and tomotherapy techniques used in the treatment of prostate cancer with target and critical organ doses to be included.

The target dose was studied with 4-and 6-field 3D-CRT, 7-field IMRT and tomotherapy techniques used to treat ten patients for prostate cancer and the dose volume histograms of critical organs were analyzed. The same target volumes, critical organs doses prescribed and treatment times for the three techniques were compared. Total dose of 76 Gy was given using 6 MV and 18 MV for 3D-CRT, 6 MV for IMRT and tomotherapy techniques.

When we compare the three techniques, for rectum V35(p:0·001), V65(p:0·001), D50(p:0·020) and D25(p:0·002), for bladder V50(p:0·027), V65(p:0·006), V100(p:0·006) and for femoral head, the V50(p:0·001) dose was found to be significantly different and more favourable in the tomotherapy technique. Significant differences were found with IMRT planning in 50% of bladder volume (p:0·002). There is no significant difference between the three techniques for doses of 100% volume of rectum and 25% of volume of bladder. The minimum dose that healthy tissue received which was outside the tumour volume was investigated.

Doses to critical organs were lower using the tomotherapy technique. However, the minimum doses that healthy tissue received were higher for the tomotherapy technique. When the beam on times were compared for all three techniques, a significant difference was found in favor of tomotherapy.

Prostate cancer is the most commonly diagnosed cancer in men and it is responsible for about 10% of all cancer mortality in Canadian men. The current ‘gold standard’ for the diagnosis of prostate cancer is a prostate biopsy and the decision on when to biopsy a patient with non-suspicious Digital Rectal Examination (DRE) result and total prostate specific antigen (tPSA) of 4–10 ng/ml can be challenging. In order to shift the treatment paradigm of prostate cancer toward more personalised and targeted therapy, there is the need for a clear system that makes its detection binary so as to decrease the rate of inaccurate detections. Therefore in recent years, there have been several investigations into the development of various biomarkers with high sensitivity and specificity for screening, early detection and personalised patient-specific targeted medicine from diagnosis to treatment of the disease.

This paper reports on nine currently available clinical biomarkers used in screening for early detection and diagnosis, to reduce the number of unnecessary biopsies, in risk assessment of aggressive disease and in monitoring treatment response of prostate cancer.

Current clinical prostate cancer biomarkers have the potential for a personalised risk assessment of aggressive disease and the risk of developing distant metastatic disease and have been proven to be useful tools to guide clinicians in personalised patient-specific targeted treatment and in the shared decision making between patients and their physicians regarding prostate biopsy and treatment. Using biomarkers to select patients with a significant probability of aggressive prostate cancer would potentially avoid premature death from the disease, while at the same time would safely preclude patients who do not require unnecessary invasive intervention.

This is a retrospective study to evaluate the efficacy and safety of routine use of electronic portal imaging device (EPID) in intensity-modulated radiation therapy for localised prostate cancer.

Data from 20 patients with localised prostate cancer treated by radical radiotherapy using intensity-modulated technique in Habib Bourguiba Hospital were analysed to define the action levels for pretreatment planer dose distribution of 100 treatment fields and the set-up errors of 418 portal imaging. Pretreatment planar dose distribution was measured with the EPID. The additional dose from repeated portal imaging was determined with treatment planning system.

For all 100 fields, the predicted and the measured planar dose distribution agrees well with mean±standard deviation value for γmax=2·31±0·57, γavg=0·36±0·07 and γ%≤1=98·94%±0·71%, respectively. For the evaluation of set-up errors, the mean total errors with 1 SD in the lateral, longitudinal and vertical directions were 0·11±0·44 cm; 0·02±0·37 cm and −0·02±0·21 cm, respectively. The imaging additional dose was evaluated as 1 cGy per monitor unit.

EPID is a useful tool to verify pretreatment dose distribution and to assess the correct field position without a significant increase in the absorbed dose due to the repetition of portal imaging.

Accurate localisation of target position is crucial when using techniques with sharp dose fall off such as volumetric modulated arc therapy (VMAT). Gold seed fiducial markers have been used for target localisation in image-guided radiation therapy for various tumors including intact prostate cancers. However, their role for target localisation in post-prostatectomy radiotherapy is unclear. This study was undertaken to determine the feasibility and effectiveness of gold seed fiducial markers in patients undergoing prostate bed VMAT.

The institutional radiation oncology database was used to analyse the treatment data of 18 post-prostatectomy patients with implanted gold seed fiducial markers. The shifts of the fiducial markers were reviewed, tabulated and statistically analysed.

Three hundred and eighty-six orthogonal pair images for 18 patients were reviewed. Specifically, the average gold seed fiducial shifts were 0·34 cm in the superior–inferior (S/I) axis (0·31 SD), 0·31 cm (0·29 SD) in the anterior–posterior (A/P) axis and 0·28 cm (0·25 SD) in the lateral axis (R/L). As a result, the 95% probability of fiducial marker displacement was 0·96 cm in the S/I, 0·89 cm in the A/P and 0·78 cm in the R/L axes. The most frequent shifts occurred in the inferior, left and posterior directions. The percentage of shifts more than 0·5 cm were 19·74, 21·56 and 12·47% for the S/I, A/P and R/L axes, respectively.

In the absence of fiducial markers, non-uniform planning target volume (PTV) margins of 1 cm for S/I, 9 mm for A/P and 8 mm for the lateral direction are necessary for target localisation in post-prostatectomy radiotherapy. By improving prostate bed localisation, gold seed fiducial markers can decrease PTV margins, reduce normal tissue radiation exposure and allow for dose-escalated and/or hypofractionated radiotherapy to be considered in appropriate clinical scenarios.

This study attempts to investigate fiducial marker (FM) migration and calculate the prostate planning target volume (PTV) margin considering the setup errors after translation corrections alone (T) and translation plus rotational corrections (T+R) and anatomy variation with respect to the corrected fiducial position, analysed on cone beam computed tomography (CBCT) images.

CBCT images from 25 patients are analysed for FM movements, setup error and anatomy variation with respect to the seed match positions. Systematic and random components of setup error and prostate movements are used to calculate the PTV margin for CBCT-based FM localisation in two scenarios, translation corrections only and translation plus rotational correction. MTNW887825 soft tissue gold markers (Civco, Orange City, FL, USA) were used with the department-specific immobilisation system and rectal and bladder filling protocols.

The average directional inter-marker distance variation is −0·05 ± 0·90 mm. The systematic setup errors for T+R are 0·40, 0·63 and 0·80 mm in right–left (RL), anterior–posterior (AP) and superior–inferior (SI), respectively. The corresponding values for T only are 0·54, 0·69 and 0·90 mm. The systematic prostate movement from T+R corrected FM positions are 0·65, 1·27 and 1·32 mm in the RL, AP and SI directions.

Minimal FM movements are noted from the study. The PTV margins to incorporate the daily T+R corrected setup error and prostate deformation are found to be 2·5, 4·5 and 5·2 mm in the RL, AP and SI directions, respectively. The corresponding margins for T only corrected scenario are found to be 2·8, 4·8 and 5·7 mm.

A comparative study was performed about the plan parameters and quality indices between volumetric arc therapy (VMAT) and intensity-modulated radiotherapy (IMRT) for the treatment of high-risk prostate cancer patients. The aim of this retrospective study was to compare the two methods of external beam radiotherapy IMRT and VMAT in terms of plan quality and efficacy.

Fifteen high-risk prostate patients were planned for radiotherapy using 6 MV photon. Three dose levels were contoured having Planning Tumour Volume 1 (PTV1 = 48 Gy), Planning Tumour Volume 2 (PTV2 = 57.6 Gy) and Planning Tumour Volume 3 (PTV3 = 60 Gy). Setup margins were given using the CHIP trial method. The prescribed PTV3 dose was 60 Gy in 20 fractions which is biologically equivalent to 74 Gy in 37 fractions using α/β = 3. In case of IMRT, seven fixed beam angles 30, 60, 105, 180, 255, 300 and 330 were used and the dose was optimised using the sliding window method. In case of rapid arc technique, one or two full arcs were used for dose optimisation while keeping all the dose constraints and other planning parameters same used in IMRT. The plan evaluation parameters and Organ at risks (OARs) doses were calculated using a dose volume histogram (DVH).

The average D2, D5, D95 and PTVmean for PTV3 were 61.22, 61.13, 58.12, 60.00 Gy and 62.41 62.24 59.53 61.12 Gy for IMRT and VMAT, respectively. The averages V60 for bladder and V30 for rectum were 22.81, 25 and 67, 65% for IMRT and VMAT, respectively. The average homogeneity index (HI), conformity index (CI) and gradient index (GI) were 1.04, 1.4833, 14.79 and 1.04, 1.704, 7.89 for IMRT and VMAT, respectively.

VMAT takes less dose-delivery time and lesser number of monitoring units than IMRT, thus it compensates the intrafractional movements during dose delivery. The Dose GI in VMAT was much better than IMRT. This indicates sharper dose fall off near the normal tissue. No other major differences were observed in terms of plan evaluation parameters between IMRT and VMAT techniques. So, we conclude that VMAT technique is more efficient than IMRT in terms of plan quality and dose delivery.

Dose distribution index (DDI) is a treatment planning evaluation parameter, reflecting dosimetric information of target coverage that can help to spare organs at risk (OARs) and remaining volume at risk (RVR). The index has been used to evaluate and compare prostate volumetric modulated arc therapy (VMAT) plans using two different plan optimisers, namely photon optimisation (PO) and its predecessor, progressive resolution optimisation (PRO).

Twenty prostate VMAT treatment plans were created using the PO and PRO in this retrospective study. The 6 MV photon beams and a dose prescription of 78 Gy/39 fractions were used in plans with the same dose–volume criteria for plan optimisation. Dose–volume histograms (DVHs) of the planning target volume (PTV), as well as of OARs such as the rectum, bladder, left and right femur were determined in each plan. DDIs were calculated and compared for plans created by the PO and PRO based on DVHs of the PTV and all OARs.

The mean DDI values were 0·784 and 0·810 for prostate VMAT plans created by the PO and PRO, respectively. It was found that the DDI of the PRO plan was about 3·3% larger than the PO plan, which means that the dose distribution of the target coverage and sparing of OARs in the PRO plan was slightly better. Changing the weighting factors in different OARs would vary the DDI value by ∼7%. However, for plan comparison based on the same set of dose–volume criteria, the effect of weighting factor can be neglected because they were the same in the PO and PRO.

Based on the very similar DDI values calculated from the PO and PRO plans, with the DDI value in the PRO plan slightly larger than that of the PO, it may be concluded that the PRO can create a prostate VMAT plan with slightly better dose distribution regarding the target coverage and sparing of OARs. Moreover, we found that the DDI is a simple and comprehensive dose–volume parameter for plan evaluation considering the target, OARs and RVR.

The aim of this study is to investigate the impact of anatomical changes in prostate cancer patients on the target coverage when using 6 MV beams-VMAT therapy and to propose strategies that allow us to evaluate the dose or correct it by normalization without having to perform a new simulation.

Ten patients of high-risk prostate cancer were chosen for the study. All test plans were delivered using the same isocenter and monitor units as the original plan and compared against the original unedited plan. The expansion and contraction of body contours due to size changes was mimicked by increasing and decreasing the body contour with depths of −2, −1·5, …, 1·5, 2 cm, in the anterior, and both lateral directions of the patient. A total of 90 plans were evaluated, 9 for each patient. Dose-volume histogram statistics were extracted from each plan and normalized to prescription dose.

Weight changes resulted in considerable dose modifications to the target and critical structures. Plans were found to be varied with 2·9% ± 0·3% per cm SSD change for VMAT treatment with a correlation index close to one. Therefore, doses variations were linear to the changes of depth. Gamma index evaluation was performed for the 10 renormalized plans. All of them passed criteria of 3%/3 mm in at least 98.2% of points. Eight of them passed criteria in 99% points. Gamma index 4%/4 mm passed 100% points in all patients for the chosen region of interest.

The dosimetry estimation presented in this study shows important data for the radiation oncology staff to justify whether a CT rescan is necessary or not when a patient experiences weight changes during treatment. Based on the results of our study, discrepancies between real dose and planned dose were >5% for 1·7 cm of difference in external contour in the anterior and both lateral directions of the patient.