Prostate cancer is the most commonly diagnosed cancer in men and it is responsible for about 10% of all cancer mortalities in both American and Canadian men. At present, serum prostate-specific antigen levels remain the most commonly used test to detect prostate cancer, and the standard and definitive diagnosis of the disease is via prostate biopsy. Conventional tissue biopsies are usually invasive, expensive, painful, time-consuming, and unsuitable for screening and need to be consistently evaluated by expert pathologists and have limited repeatability. Consequently, liquid biopsies are emerging as a favourable alternative to conventional tissue biopsies, providing a non-invasive and cost-effective approach for screening, diagnosis, treatment and monitoring of prostate cancer patients.

We searched several databases from August to December 2020 for relevant studies published in English between 2000 and 2020 and reporting on liquid-based biomarkers available in detectable quantities in patient bodily fluid samples. In this narrative review paper, we describe seven novel and promising liquid-based biomarkers that potentially account for individual patient variability as well as used in disease risk assessment, screening for early disease detection and diagnosis, identification of patients’ risk for metastatic disease and subsequent relapse, monitoring patient response to specific treatment and providing clinicians the potential to stratify patients likely to benefit from a particular treatment.

The concept of precision medicine from prevention to treatment techniques that take individual patient variability into account will depend on the development of effective clinical biomarkers that interrogate key aberrant pathways potentially targetable with molecular targets or immunologic therapies. Liquid-based biomarkers with high sensitivity and specificity for prostate cancer are emerging as minimally invasive, lower risk, readily obtainable and easily repeatable technique for screening for early disease detection and diagnosis, patient stratification at diagnosis into different risk categories, identification of patients’ risk for metastatic disease and subsequent relapse, and real-time monitoring of patient response to specific treatment. Thus, effective liquid-based biomarkers will potentially shift the treatment paradigm of prostate cancer towards more personalised and targeted medicine.

To evaluate and develop an image-guided radiotherapy (IGRT) protocol for the effective treatment of prostate and pelvic lymph nodes.

This study comprised of nine patients receiving radiotherapy for node negative prostate cancer, who had a pair of planar kV images taken for 37 treatment fractions. The positioning accuracy for both implanted fiducial markers and pelvic bony anatomy (surrogate for pelvic node position) was calculated using random and systematic errors. Appropriate margins were also determined. All patients followed a strict bladder and bowel protocol before computed tomography planning and treatment.

In total, 292 sets of images were used for fiducial marker and pelvic bone registration. A discrepancy of >5 mm between the fiducial markers and the anatomical pelvic bone was seen in 4% of treatment sessions. The maximum displacement observed between the fiducial match and the bone match was 7, 10 and 4 mm in the A/P (anterior/posterior), S/I (superior/inferior) and R/L (right/left) directions, respectively.

The margins used in combination with an online IGRT strategy ensure both the fiducial match and the bone match correlate within 5 mm thus allows good coverage of both prostate and nodal target volumes. It is essential that this is combined with a strict bladder and rectal preparation protocol to ensure accuracy and reproducibility.

This study aimed to investigate the uncertainty in organ delineation of low-dose computed tomography (CT) images using a high-strength iterative reconstruction (IR) during radiotherapy planning for the treatment of prostate cancer.

Two CT datasets were prepared with different dose levels by adjusting the reconstruction slice thickness. Two observers independently delineated the prostate, seminal vesicles, bladder and rectum on both images without referring to other modality images. The delineated organ volumes were compared between both images. Observer delineation variability was assessed using Dice similarity coefficient (DSC) and mean distance to agreement.

No significant differences regarding the delineated organ volumes were observed between the low- and standard-dose images for all organs. Regarding inter-observer variability, the DSC was relatively high for both images, whereas mean distance to agreement was not significantly different between images (p > 0·05 for all). Intra-observer variability for each observer showed high DSC (>0·8 and >0·9 for seminal vesicles and other organs, respectively) but no significant differences in the mean distance to agreement (p > 0·05 for all).

Our results indicate that low-dose CT images with high-strength IR would be available for organ delineation in the radiotherapy treatment planning for prostate cancer.

Prostate positional variability has been widely explored with seminal vesicle (SV) variability, coming into the forefront only in recent years. While planning target volume (PTV) margins and preparation protocols ameliorate the effects of bladder and rectum volume changes on prostate, studies on SV variation have looked at only position, not volume variability.

The aim of this study was to investigate whether the inter-fraction volume variability of the VSs can exist in patients receiving radiotherapy to the prostate.

SV variability was investigated by comparing four on-treatment cone beam computer tomography scans to a planning computer tomography (CT) image for two patients receiving prostate radiotherapy. For each case, variation in volumes (cm3) was compared with intra-observer variation.

SV volume variability was seen in both patients, with the largest change in volume being 78·38%. This variance was considerably (between 2 and 10 times) larger than the measured intra-observer variance.

This study identified the potential for daily SV volume variability in patients receiving prostate radiotherapy. Future large-scale studies are warranted to identify the extent of this motion and potential clinical impact. Evidence-informed PTV margins and possible SV volume control protocols may need to be adopted.

To evaluate changes of accumulated doses from an initial plan in each fraction by deformable image registration (DIR) with daily megavoltage computed tomography (MVCT) images from helical tomotherapy for prostate cancer patients.

The MVCT images of five prostate cancer patients were acquired by using a helical tomotherapy unit before the daily treatment fraction began. All images data were exported to DIR procedures by MIM software, in which the planned kilovoltage computed tomography (kVCT) images were acting as the source images with the daily MVCT acquired as the target images for registration. The automatic deformed structure was used to access the volume variation and daily dose accumulation to each structure. All dose-volume parameters were compared to the initial planned dose.

The actual median doses of the planning target volume (PTV) received 70 Gy and 50.4 Gy were decreased at the end of the treatment with an average 1·0 ± 0·67% and 2·1 ± 1·54%, respectively. As regards organs at risk (OARs), the bladder and rectum dose-volume parameters tended to increase from the initial plan. The high-dose regions of the bladder and rectum, however, were decreased from the initial plan at the end of the treatment.

The daily actual dose differs from the initial planned dose. The accumulated dose of target tends to be lower than the initial plan, but tends to be higher than the initial plan for the OARs. Therefore, inter-fractional anatomic changes should be considered by the DIR methods, which would be useful as clinically informative and beneficial for adaptive treatment strategies.

High-risk prostate cancer is the most common presentation at our institute among patients with non-metastatic prostate cancer. Traditionally, pelvic lymph nodes were given a prophylactic dose of radiotherapy while the prostate was given a curative dose of radiation. This study aims to evaluate patterns of failure in patients who had prostate-only radiation at our centre.

All high-risk prostate cancer patients who underwent radical radiotherapy to prostate only since 2014 were retrospectively analysed. Local T stage, baseline prostate-specific antigen (PSA) and Gleason score were recorded. Bone scan and staging CT scan data were collected. Various dose levels prescribed to prostate were analysed. The follow-up records of these patients were assessed. Patients who failed in pelvic lymph nodes were recorded separately. Overall survival and failure-free survival were calculated using Kaplan–Meier curve.

One-hundred five patients fulfilling the inclusion criteria were analysed. Only three patients developed recurrence in pelvic lymph node following prostate-only radiotherapy (PORT). Five year overall survival was 77% while failure-free survival was 64%. Forty patients had a PSA failure after a median follow-up of 62 months.

Most high-risk prostate cancer patients who progress following hormone therapy and PORT have metastases outside pelvis. Till further conclusive evidence is available PORT can be considered as a safe option.

The purpose of this study was to develop the patient-specific quality control (QC) process by most commonly used dosimeters in Bangladesh and recommend a suitable passing rate for QC, irrespective of the dosimetric tools used.

Intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) plans of five head-and-neck (HN) and five prostate patients were selected for the patient-specific QC. These plans were generated using the Eclipse TPS v11·0 (Varian Medical Systems, Inc., Palo Alto, CA, USA) 6 MV X-ray from a Varian TrueBeam linear accelerator (Varian Medical Systems, Inc.) for each case. Each IMRT and VMAT plans were measured by two-dimensional (2D) ion chamber arrays (I’matriXX) and electronic portal imaging devices (EPID), respectively. The passing rates of the dosimetric tools were calculated using criteria of 3%/3 mm.

The average passing rates (±SD) of I’matriXX for prostate and HN were 97·9±0·76 and 98·88±0·24, respectively. For VMAT verification, the average passing rates of EPID for prostate for arc1 and arc2 were 96·15±0·49 and 97·8±0·70, respectively; similarly, for HN the rates were 97·85±0·63 and 97·2±0·56, respectively.

The results showed that both the dosimeters can be used in patient-specific QC, although the EPID-based IMRT and VMAT QC is more advantageous in terms of time-saving and ease of use. Hence, for patient-specific QC, one can use the ion chamber arrays (I’matriXX) or EPID in hospital, but the systems need to be cross-checked.

Although manual adjustment of automatic cone beam computed tomography (CBCT) matching may improve the target coverage in certain points of interest, concerns exist that this may lead to dosimetric uncertainties which would negate the theoretical benefit of this approach. The objective of this study is to evaluate the dosimetric impact of manual adjustments made after automatic bony registration on CBCT in prostate patients.

A total of 50 CBCT datasets of ten high-risk prostate cancer patients were randomly chosen. Each CBCT dataset was registered three times. Method (A): Automatic registration, Method (M1): Manual adjustment carried out by two experienced radiation therapists, Method (M2): Manual adjustment carried out by different radiation therapists with varying levels of experience. The clinical target volume (CTV), planning target volume (PTV), the bladder and the rectum were subsequently contoured on each CBCT dataset by a radiation oncologist blinded to the registration methods. The absolute difference of various dosimetric parameters were then analysed and compared with the original planning doses. A comparison of the three matching methods employed was also carried out.

There was a statistically significant difference in the magnitude of move taken in the inferior superior direction between M1 and M2 method. There were no significant differences observed in any of the dosimetric parameters examined in relation to the rectum, bladder or CTV. The only significant difference observed was the volume of PTV covered by the prescription isodose (95%) which was statistically significant lower in method A compared with both M1 and M2. There was no difference observed between M1 and M2 methods. The mean duration of the automated registration and subsequent analysis was 64 seconds compared with 91 seconds for automated registrations which included the additional manual adjustment.

CBCT-based manual adjustments of automated bony-based registrations during the image-guided radiotherapy verification of prostate cancer patients can improve PTV coverage without impacting negatively on the doses received by the organs at risk. This strategy is associated with a small increase in overall treatment time.

Sexual dysfunction is a common side effect of external beam radiotherapy (EBRT) and androgen deprivation therapy (ADT) to treat prostate cancer. Men are likely to experience erectile dysfunction, low libido, ejaculatory problems and penile shortening. This qualitative study explored men’s perceptions of sexual dysfunction, including factors such as self-perception, relationships and information and support needs.

Semi-structured interviews were carried out with n = 8 men living 18–30 months after EBRT ± ADT. The interviews were transcribed and thematic analysis was carried out.

All men experienced sexual dysfunction following treatment. The main themes arising were: (i) priorities—sexual issues were not a priority when making treatment decisions, (ii) information and support—men described a lack of information and support about sexual dysfunction and (iii) impact—sexual dysfunction impacted on their self-perception and relationships.

Men undergoing EBRT/ADT for prostate cancer may be affected by post-treatment changes in sexual function in a range of ways. This study suggests that they would benefit from early and wide-ranging information and support on sexual dysfunction, even if they do not consider it as a priority. Candid discussions about self-perception and relationships, as well as physical changes, may equip them to cope with post-treatment changes.

The Varian Trilogy linear accelerator’s multi-leaf collimator moves on a carriage with a maximum leaf span of 15 cm. The traditional open and limited X-jaw technique of volumetric-modulated arc radiotherapy (VMAT) yields a relatively compromised dose distribution within the planning target volume (PTV) region. This study aimed to determine whether the split X-jaw planning technique for VMAT improves plan quality regarding target dose coverage and organs at risk (OAR) sparing for PTVs that require a field size of more than 15 cm in the X-jaw direction in prostate cancer patients.

Computed tomography data sets from 15 patients with prostate cancer were enrolled in the study. Only the PTVs requiring a field size larger than 18 cm in the X-jaw position were considered, and a dose of 4500 cGy in 25 fractions was prescribed. For each case, three separate treatment plans were generated: open, limited and split X-jaw planning techniques with similar planning objectives

The split X-jaw technique resulted in statistically significant superior coverage of PTV when compared with the open (P < 0·0001) and limited methods (P < 0·001). The split technique delivered a lower dose to the OARs, although statistical significance could not be achieved. D2% (cGy) was lowest for the PTV in the split technique (4684·8 ± 18·16) and highest for the open technique (4710 ± 18·75), P < 0·001.

The x-split jaw technique can replace the traditional open X-jaw practice of VMAT for PTVs requiring an X-jaw width of more than 15 cm in the Varian linear accelerator.

The aim of this work was to study the acceptability of plans prepared for prostate patients treated by volumetric modulated arc therapy (VMAT) with the vision to evaluate the quality of plans and test pre-treatment quality assurance (QA).

VMAT plans of 35 patients, planned on the Eclipse Treatment Planning System (Aria 15), were included in the study. Plan acceptability was checked using statistical analysis, which includes homogeneity index, radical and median homogeneity index, coverage and uniformity index. Dose–volume histograms (DVH) of the plans were also studied to check prescribed dose (PD), Dmax, Dmin, D5 and D95. Portal dosimetry was also done by gamma analysis using 3%/3 mm criterion. SD and mean SD error were also calculated and analysed.

Statistical analysis showed a mean HI of 1·054, coverage 0·959, UI 1·055, mDHI 0·962 and rDHI 0·866. SD of HI, coverage, UI, mDHI and rDHI was 0·019, 0·019, 0·014, 0·013 and 0·030, respectively. From the DVHs, mean of D5, D95, Dmin and Dmax was calculated at 6,252·9, 5,757·4, 6,413·3 and 5,657·7 cGy, respectively, with a prescribed dose of 6,000 cGy. According to gamma analysis, area gamma < 1 was 99·12% with a tolerance limit of 95%, maximum gamma was 1·466 with a tolerance limit of 3·5, average gamma was 0·388 with a tolerance limit of 0·5, area gamma > 1·2 was 0·242% with a tolerance limit of 0·5%, maximum dose difference was 0·6 with a tolerance limit of 1·0 and average dose difference was 0·029 with a tolerance limit of 0·2.

All three computations showed the results to be within acceptable limits. VMAT possesses a unique feature of delivering the whole treatment with only two rotations of the gantry. VMAT has an improved efficiency of delivery for equivalent dosimetric quality.

Electronic portal imaging device (EPID) offers high-resolution digital image that can be compared with a predicted portal dose image. A very common method to quantitatively compare a measured and calculated dose distribution that is routinely used for quality assurance (QA) of volumetric-modulated arc therapy (VMAT) and intensity-modulated radiation therapy treatment plans is the evaluation of the gamma index. The purpose of this work was to evaluate the gamma passing rate (%GP), maximum gamma (γmax), average gamma (γave), maximum dose difference (DDmax) and the average dose difference (DDave) for various regions of interest using Varian’s implementation of three absolute dose gamma calculation techniques of improved, local, and combined improved and local.

We analyzed 232 portal dose images from 100 prostate cancer patients’ VMAT plans obtained using the Varian EPID on TrueBeam Linacs.

Our data show that the %GP, γmax and γave depend on the gamma calculation method and the acceptance criteria. Higher %GP values were obtained compared with both our current institutional action level and the American Association of Physicists in Medicine Task Group 119 recommendations.

The results of this study can be used to establish stricter action levels for pre-treatment QA of prostate VMAT plans. A stricter 3%/3 mm improved gamma criterion with a passing rate of 97% or the 2%/2 mm improved gamma criterion with a passing rate of 95% can be achieved without additional measurements or configurations.

Intensity-modulated radiation therapy (IMRT) treatment delivery requires pre-treatment patient-specific quality assurance (QA) for the dosimetry verification due to its complex multileaf-collimator movement. The prostate target close position between the bladder and rectum requires a tight margin during planning, and mistreatment would have a huge impact on the patient. A commercially available QA tool consists of a homogeneous medium and does not represent an exact photon interaction on the tumour and also on the nearby healthy organ.

A heterogeneous male pelvis phantom was developed and investigated the efficiency of the treatment planning system (TPS) calculation on the off-axis region.

Polymethyl methacrylate was used for the phantom housing, and the material closed to the bladder, rectum and prostate density was chosen to construct the organ models. The phantom was scanned and validated by the computed tomography number and density. An IMRT treatment was planned in the Monaco TPS, and a thermoluminescent dosimeter (TLD-100) was used to validate the point dosimetry. In addition, an EGSnrc Monte Carlo simulation was carried out to validate the phantom dosimetry.

The dose measurement between TLD-100, TPS, and EGSnrc was compared and validated in the pelvis phantom. In the prostate region, the dose difference was within ± 5%, and the maximum dose difference outside-the-irradiated field was up to 20·07 % and 47·31 % in TPS and TLD-100, respectively. Meanwhile, the measured dose was lower than the calculated dose, and it was apparent for the dose outside-the-irradiated field.

The developed heterogeneity male pelvis phantom was validated and verified to be an important QA device for validating radiation dosimetry in the pelvis region. The dose outside-the-irradiated field was underestimated by both TPS and TLD, respectively.

Prostate cancer is a common malignancy with rising incidence in Western countries such as the United Kingdom. In localised disease there are a variety of curative treatment modalities. Patients can be referred for surgery, or for a combination of hormonal therapies and radiotherapy (external beam radiotherapy or brachytherapy). Each treatment option comes with side effects and in the case of radiotherapy one potential complication is bowel toxicity from radiation exposure. New technologies are being developed to try and mitigate the side effects and long term morbidity of this treatment, and to expand access to radiotherapy for patients who may previously have been excluded (i.e those with inflammatory bowel disease). Rectal Spacers are absorbable polyethylene glycol hydrogels injected into the perirectal space. These position the anterior rectal wall away from the prostate, subsequently minimising radiation dose to the rectum. Rectal Spacers have been introduced to National Healthcare Service (NHS) practice as part of the Innovation and Technology Payment (ITP) programme, however, their use is now under review.

In this editorial we conduct a narrative review of some of the available evidence for Rectal Spacers, discuss their utilization within the NHS and the barriers to their wider use. We also explore preliminary dosimetry and quality of life data for use of Rectal Spacers in our centre where we have been part of the NHS ITP programme. Dosimetry data and Quality of life questionnaires were gathered from 22 treated patients and 11 matched controls. This indicated lower radiation doses to the prostate in those treated with Rectal Spacers.

Rectal Spacers are an effective method to reduce radiation dose to the prostate in men treated for localised prostate cancer, however, their use remains under review in the NHS and there are a variety of barriers to upscaling their use.

The study aimed to assess the clinical feasibility of employing an automatic match during cone beam computed tomography (CBCT) imaging using prostatic calcifications within the 95% isodose set as the region of interest.

CBCT images were analysed on the 5th fraction in 34 patients evaluating the difference between standard manual soft tissue anatomy matching versus auto calcification matching. An assessment of the clinical feasibility of using prostatic calcifications during matching alongside considering the effect a more automated matching process has been conducted on interobserver variability.

The standard deviation values of the difference between the soft tissue match (baseline) versus automatic calcification matches fluctuated around 1 mm in all three axes for all of the matches carried out. The interobserver variability observed between the two radiographers was 0·055, 0·065 and 0·045 cm in the vertical, longitudinal and lateral axes, respectively.

The clarity of the calcifications on the CBCT images might explain the low interobserver variability displayed by the two matching radiographers. A calcification provides a clear starting point for image matching before commencing a check of volumetric coverage, if the matching process begins in the same place, it can allow for a standardisation of matching technique between radiographers.

Prostate cancer is the most commonly diagnosed malignancy and the third leading cause of death among Canadian men. The standard treatment modalities for prostate cancer include prostatectomy, radiation therapy, hormonal therapy and chemotherapy or any combination depending on the stage of the tumour. However, several studies have reported that tobacco smoking at the time of diagnosis and during treatment can potentially impact treatment efficacy, outcome and patients quality of life after treatment.

This narrative literature review elucidates the impacts of tobacco smoking on prostate cancer progression, treatment efficacy, including its effects on prostatectomy, radiation therapy and chemotherapy, risk of cancer recurrence and mortality and quality of life after treatment. Furthermore, we discuss the importance of integrating a smoking cessation programme into the treatment regimen for prostate cancer patients in order to yield more favourable treatment outcomes, reduce risk of recurrence and mortality and increase the quality of life after treatment for prostate cancer patients.

Smoking cessation is one of the most important interventions to prevent cancer and it is also essential after the diagnosis of prostate cancer to improve clinical outcomes. All prostate cancer patients should be advised to quit tobacco use since it can potentially improve treatment response rates and survival, as well as reduce the risk of developing treatment complications and potentially improve the quality of life after treatment. There are several benefits to smoking cessation and it should become an important component of the cancer care continuum in all oncology programmes, starting from prevention of cancer through diagnosis, treatment, survivorship and palliative care. Evidence-based smoking cessation intervention should be sustainably integrated into any comprehensive cancer programme, and the information should be targeted to the specific benefits of cessation in cancer patients.

Patients undergoing prostate radiation therapy were observed to have elevated blood pressures in clinic. Therefore, we sought to further characterise this phenomenon.

The charts of 76 patients who received radiotherapy for prostate cancer between 2014 and 2017 were examined. Blood pressure (BP) readings were obtained at initial consultation, on treatment visits, and subsequent follow-up appointments. To describe this effect, we defined radiation-associated hypertension (RAH) as an increase ≥15 mmHg systolic BP, 10 mmHg diastolic BP, or 5 mmHg mean arterial pressure.

Within this cohort, 36 patients developed RAH, with 75% developing RAH while on treatment, and 25% developing RAH at post-treatment visits. Two-thirds of patients remained hypertensive during post-treatment visits, and 27% were prescribed additional anti-hypertensives. There was no association between neoadjuvant/concurrent androgen deprivation therapy and RAH.

A significant number of patients undergoing prostate radiotherapy developed RAH, necessitating additional medication in some.

The aim of this study was to evaluate planning target volume (PTV) margins for two different locations using an electronic portal imaging device (EPID) to ensure that the correct radiation dose is delivered to the tumour when using intensity-modulated radiation therapy (IMRT).

Setup data were collected from 40 patients treated with IMRT for head and neck cancer (HN) (20 patients) and prostate cancer (20 patients). Setup errors from 720 registration images were analysed to evaluate systematic and random errors. Thereafter, optimal PTV margins were calculated based on International Commission on Radiation Units and Measurements 62 (ICRU), Stroom and Parker formulas compared with the Van Herk’s recipe.

To calculate the margins around the PTV, several different formulas have been used. Setup margins ranged between 2–4·3, 2·2–4·6 and 2·1–4·7 mm in X, Y and Z directions, respectively, for HN cases. Similarly, for the prostate site, setup margins ranged between 3·7–8·3, 3·2–6·8 and 3·3–8·2 mm in X, Y and Z directions.

To ensure better coverage of target volume, we adopted a PTV margin of 5 mm for HN PTVs and 10 mm for prostate PTVs in our department.

Radiotherapy clinical trials are at the forefront of modern-day prostate cancer patient management. Patients are reviewed during treatment by clinical oncologists or competent on-treatment review radiographers to minimise treatment toxicities. Clinical Research Radiographers (CRRs) routinely monitor and gather research data from patients participating in clinical trials.

The aim of this article is to evaluate the effectiveness of the CRR undertaking the on-treatment review of clinical trial patients.

An experienced CRR within the Northern Ireland Cancer Trials Network was supervised by a clinical oncologist to undertake the role of the on-treatment review of patients receiving radiotherapy for prostate cancer. The CRR explored published literature and compiled this written evaluation as part of their advanced practice learning.

The supervising clinical oncologist verified, following the planned period of supervised practice and academic study, that the CRR was competent to fulfil the role. Evidence of the beneficial synergistic impact of co-joining the roles was experienced at first hand during the undertaking of supervised practice.

Co-joining the roles and responsibilities of the CRR and the on-treatment review radiographer enhanced the quality of care offered to the patients participating in clinical trials.

Radiation therapy has historically used margins for target volume to ensure dosimetric planning criteria. The size of margin for a given treatment site is still uncertain particularly for moving targets along with set-up variations leading to a fuzziness of target volume. In this study, we have estimated the dosimetric benefit of normal structures using biological-based optimal margins. The treatment margins are derived by knowledge-based fuzzy logic technique which is considering the radiotherapy uncertainties in treatment planning.

All treatment plans were performed using stepped increments of asymmetric margins to estimate prostate radiobiological indices such as tumour control probability (TCP) and normal tissue complication probability (NTCP). An absolute NTCP of 5% was considered to be the maximum acceptable value while TCP of 85% was considered to be the minimal acceptable limit for each volumetric modulated arc therapy (VMAT) plan of localised prostate cancer radiotherapy. Results were used to formulate rules and membership functions for Mamdani-type fuzzy inference system (FIS). In implementing the rules for the fuzzy system for ΔNTCP values above 10%, the PTV margin was not permitted to exceed 5 mm to avoid rectal complications due to margin selection. The new margins were applied in VMAT planning of prostate cancer for standard displacement errors. The dosimetric results of normal tissue predictors were estimated such as organ mean doses, rectum V60 (volume receiving 60 Gy), bladder V65 (volume receiving 65 Gy) and other clinically significant dose–volume indicators and compared with VMAT plans using current margin formulations.

Dosimetric results compared well to the results obtained by current techniques. Good agreement was obtained between proposed fuzzy model margins and currently used margins in lower error magnitude, but significant results were observed at higher error magnitude when organ toxicity concerned without compromising the target volumes.

The new margins may be helpful to estimate possible outcomes of normal tissue complications and thus may improve complication free survival particularly when organ motion errors are inevitable, case by case.