Wilms tumor (WT) is the most common renal malignancy in children, with a peak incidence between the ages of 3 and 4 years. This study aimed to evaluate the clinicopathological features, treatment characteristics and survival outcomes of patients managed for WT at the study site.

This was a quantitative cross-sectional study involving 137 pediatric patients diagnosed with and managed for WT between 2012 and 2021. Total population sampling was used for participant selection. Data were analyzed using SPSS software, with Kaplan-Meier and Cox regression analysis used to estimate survival rates and examine prognostic factors. P-values < 0·05 were considered statistically significant.

The 2- and 5-year overall survival (OS) rates were 75% and 70%, respectively, while the disease-free survival (DFS) rates at 2- and 5-years were both 79%. Pathological staging significantly impacted OS and DFS (p = 0·000), while age, gender, weight and risk stratification did not show statistically significant differences. The left kidney was the most common primary site (51%), with an even male to female gender ratio of 1:1. Metastases were most common in the chest (n = 19, 13·8%) and lungs (n = 13, 9·5%).

Pathological stage was the most significant prognostic factor for both OS and DFS, emphasizing the importance of early detection and timely intervention. While the 2- and 5-year OS and DFS rates represent an improvement over previous studies in Ghana, they remain suboptimal compared to outcomes in high-income countries. A holistic, coordinated institutional treatment regimen has enhanced patient compliance, survival outcomes and follow-up care.

Radiotherapy is a critical component of head and neck cancer (HNC) management that requires reliable patient immobilization. Using thermoplastic masks helps to ensure reproducible patient positioning during radiotherapy, thus reducing the risk of a geographical miss. However, the use of these masks can also induce anxiety and distress, which can negatively impact treatment adherence and quality of life outcomes.

The research was a quantitative cross-sectional study that determined the prevalence and severity of thermoplastic mask-induced anxiety and assessed the scope of coping mechanisms used by HNC patients. Data were collected using a structured questionnaire from recruited participants and analysed with the Statistical Package for Social Sciences software, version 26·0. Relevant clinical and treatment-related data were retrieved from patients’ hospital-based medical records. Descriptive and inferential statistical analyses such as chi-square tests and likelihood ratios were conducted, with p-values < 0·05 considered statistically significant.

In all, there were 145 HNC patients with a male to female ratio of 1·9:1 and a median age of 52·8 years (IQR 20·7), ranging from 18 to 82 years. There was a high prevalence of thermoplastic mask-induced anxiety both during mask moulding (93·8%) and radiation therapy sessions (94·5%). Most participants (95·2%) adopted coping mechanisms including distraction (58%) and visualization techniques (46%).

Even though there was a high level of awareness and utilization of coping mechanisms, the high prevalence of thermoplastic mask-induced anxiety highlights a critical aspect of HNC patient care that may be overlooked in resource-limited settings.

Given the increased risk of cardiac toxicity with higher doses, cardiac sparing is crucial for left-sided breast cancer patients. Deep inspiration breath hold (DIBH) is one approach, but its reproducibility is questioned. This study evaluates the reproducibility of DIBH with an active breathing coordinator (ABC) device, focusing on its dosimetric impact in maintaining consistent cardiac sparing for patients undergoing partial breast irradiation (PBI).

Thirty-three patients undergoing PBI with a prescription dose of 30 Gy in five fractions were randomly selected. Each patient was treated with 6 MV photons using volumetric modulated arc therapy (VMAT) with DIBH using an ABC device. Prior to each fraction, kilo-voltage cone beam computed tomography (kV-CBCT) images were acquired to assess inter-fractional heart motion. Contours of the whole heart and left anterior descending artery (LAD) were transferred from the planning CT to CBCTs and back, using rigid alignment and isocentre shifts to represent treatment positions. Agreement between delivered and planned doses assessed DIBH reproducibility.

Throughout the entire treatment course, changes in mean and maximum cardiac doses were less than 16·4 cGy and 264·8 cGy, respectively. Changes in mean and maximum LAD doses were less than 54·0 cGy and 160·2 cGy, respectively. Overall, the mean cardiac dose increased by 2·4 ± 6·6 cGy, and the maximum by 23·3 ± 58·0 cGy. The mean LAD dose increased by 4·8 ± 18·5 cGy, and the maximum by 17·0 ± 51·0 cGy.

DIBH can be effectively reproduced with the ABC device, limiting inter-fractional cardiac dose changes.

The technological development of radiotherapy equipment enabled the changing of the dose rate over time during irradiation. Further, techniques, such as volumetric modulated arc therapy (VMAT), are becoming more widespread. This study aimed to assess the changes in radiation isocenter and beam alignment with different dose rates and investigate the dose error during VMAT plan delivery.

The Winston–Lutz (WL) test and three-dimensional water phantom profiles were measured at different dose rates using 4, 6 and 10 MV and flattening filter-free (FFF) at 6 and 10 MV of X-rays. Furthermore, the change in alignment with the dose rate was reproduced through beam parameter adjustments, and the change in dose difference (DD) in the VMAT plan was assessed.

The WL test revealed a 0·1–0·3 mm radiation isocenter displacement with dose rate. Further, the beam profile measurement results demonstrated a 0·3 mm beam centre position displacement in both the lateral and gun-target directions caused by the change in dose rate. VMAT plan delivery with a beam whose centre position changed by 0·3 mm caused a 0·2–3% decrease in the previous DD rate.

The radiation isocenter and beam alignment changed based on the dose rate. Evaluating the change in beam alignment at multiple dose rates is recommended when performing irradiation with different dose rates.

Radiotherapy aims to provide either curative treatment or palliation, with radiation transmission through shielding blocks ideally not exceeding 5% of the incident dose.

This study assessed the attenuation efficacy of Cerrobend shielding blocks, determining the thickness required for achieving 95% attenuation and evaluating the adequacy of currently used blocks.

An experimental study was conducted using a 1·25 MeV cobalt-60 teletherapy machine. Radiation intensities transmitted through Cerrobend blocks of varying thicknesses (1–5 cm) were measured with a calibrated ionization chamber and electrometer. Measurements were performed with a fixed field size of 10 cm × 10 cm at a 100-cm source-to-chamber distance, minimizing scatter. Baseline and transmitted intensities were recorded, with each measurement repeated five times for precision.

The percentage transmission, linear attenuation coefficients and thickness required for 5% transmission were calculated using regression analysis. Radiation intensity decreased exponentially with increasing Cerrobend block thickness, from 15·01 nC (0 cm) to 0·939 nC (5 cm thickness). Regression analysis showed a strong negative linear relationship (y = −0·5386x + 2·6705; R2 = 0·992). The thickness required for maximum transmission of 5% was determined to be 6 cm, while the routinely used 5 cm blocks at the study site allowed 8% transmission, exceeding the recommended threshold. Minimal environmental variations ensured measurement consistency.

The study demonstrated that 6 cm Cerrobend blocks were necessary to achieve the recommended 95% attenuation, whereas the 5 cm blocks in use resulted in suboptimal shielding. This highlights the need to revise shielding practices to improve radiation protection and patient safety in resource-constrained radiotherapy settings.

Optimal radiotherapy technique selection for left-sided breast cancer remains challenging. This study compared volumetric-modulated arc therapy (VMAT), VMAT+IMRT (VMAT+IMRT) and IMRT+VMAT (IMRT+VMAT) using an innovative integrated scoring system and risk factor (RF) assessment.

Retrospectively analysed 41 patients with left-sided breast cancer. Treatment plans were evaluated using an integrated scoring system considering tumour coverage and organs at risk (OARs) sparing. RF analysis assessed potential adverse effects on the heart and lungs. Correlation analysis explored relationships between integrated scores and risk factors.

VMAT showed the best overall integrated score (1·0931 ± 0·1707), followed by IMRT+VMAT (1·2011 ± 0·2440) and VMAT+IMRT (1·2264 ± 0·2499). VMAT had the highest percentage of Excellent OAR plans (14·6%), while VMAT+IMRT and IMRT+VMAT showed better PTV coverage (53·7% and 51·2% Excellent, respectively). RF analysis revealed: VMAT (heart RF: 0·341, lung RF: 0·671), VMAT+IMRT (heart RF: 0·294, lung RF: 0·750) and IMRT+VMAT (heart RF: 0·533, lung RF: 0·546). Correlation analysis showed strong positive correlations between integrated scores and lung RF for VMAT (r = 0·671) and VMAT+IMRT (r = 0·750), with IMRT+VMAT showing moderate correlations for lung (r = 0·546) and heart (r = 0·533) RFs.

VMAT demonstrated the best balance between PTV coverage and OAR sparing, hybrid techniques improved target coverage but increased risk to OAR. The RF analysis highlighted varying impacts on heart and lung across techniques. This analysis provides valuable insights for technique selection, potentially improving treatment outcomes and reducing complications in left-sided breast cancer radiotherapy.

Predicting radiotherapy (RT) tooth dose guides pre-RT dental management, reducing osteoradionecrosis (ORN) risk through informed extraction or treatment adjustments. This study evaluated the mean radiation dose to individual teeth for head and neck cancer (HNC) patients receiving external beam RT at the South West Wales Cancer Centre (SWWCC), to guide pre-emptive tooth extraction.

A retrospective analysis was conducted on 158 HNC RT patients treated over a 2-year period. Patients with subsites containing ≤10 patients were excluded, and larynx cases were analysed separately before exclusion due to low ORN risk, leaving 107 patients in the final analysis. Teeth were outlined using MedCom ProSoma v4.2, and treatment plans were generated with Philips Pinnacle v16.2 using volumetric arc therapy (VMAT), without dental dose optimisation. Mean doses were reported per tooth and categorised by site, staging and tooth position, with mean and standard deviations calculated. ORN risk was defined as medium (≥40Gy) and high (≥50Gy).

Larynx patients received low mean doses (<25Gy), supporting their exclusion. Base of tongue (BoT) cases showed a dose ≥40Gy for lower ipsilateral molars in T4. Oral cavity diagnosis had the highest ORN risk, with most teeth ≥40Gy in T2+ cases and ≥50Gy in later cancer staging. The oropharynx showed some higher risk doses for T4-staging. T-tests confirmed significant dose differences between upper and lower teeth.

This study provides a site-specific indicative guide for pre-RT tooth extraction based on likely dose exposure, to guide pre-radiation dental management strategies and plan optimisation decisions to reduce ORN risk.

Oropharyngeal squamous cell carcinoma (SCC) is a common type of head and neck cancer often linked to tobacco, alcohol use, and, in youngers, HPV infection. Standard care for locally advanced SCC involves radiotherapy (RT) and cisplatin, (total doses of 66–70Gy in 30–35fractions). However, some patients with significant comorbidities cannot tolerate chemotherapy, requiring alternative approaches. We present a case of a 66-year-old male with p16-negative oropharyngeal SCC and bulky cervical nodal metastasis, ineligible for chemotherapy.

The patient was treated using adaptive volumetric modulated arc therapy (VMAT) with simultaneous integrated boost (SIB) and central gross tumor volume (GTV) dose escalation. This approach delivered up to 72Gy to the central GTV in 30 fractions; 66 Gy in 30 fractions to the high-risk area; 60Gy in 30 fractions to the intermediate-risk area; 54 Gy in 30 fractions to the low-risk area.

An epithelolysis (grade 3) led to a four-day treatment pause. A mid-treatment CT showed tumor shrinkage, reducing the nodal GTV volume from 107to 33cc, prompting adaptive planning to optimize dose distribution and reduce toxicity. The patient completed RT without further interruptions. At six months post-treatment, no recurrence or severe toxicities were detected and four years post-treatment, the patient remains in complete remission without significant late toxicity.

This case demonstrates the effectiveness of VMAT with SIB in delivering accelerated radiotherapy to a bulky nodal lesion in a patient with p16-negative oropharyngeal SCC unfit for chemotherapy; This allowed for tumor control while minimizing exposure to critical structure.

Teaching volumetric modulated arc therapy (VMAT) treatment planning to therapeutic radiography students faces challenges, including time constraints and resource limitations. Gamification, an active learning strategy incorporating game-based elements, may enhance engagement and understanding of VMAT treatment planning.

A VMAT treatment planning session was implemented for 15 second-year undergraduate and postgraduate therapeutic radiography students using gamification. Participants were tasked with optimising a VMAT plan for a palliative prostate cancer patient using Eclipse treatment planning software. Students completed pre- and post-session questionnaires assessing perceived understanding and enjoyment. Plans were evaluated against clinical goals, and a leaderboard was used to rank top performers. Thematic analysis was applied to qualitative feedback.

About 86·7% of participants initially reported a limited understanding of VMAT planning structures. Post-session, all participants reported improved perceived understanding, with 93·3% finding the session beneficial and recommending its inclusion in the programme. While 66·6% enjoyed the gamified approach, technical issues limited individual optimisation time. Qualitative feedback highlighted increased confidence and engagement despite challenges.

Gamification enhanced student-reported understanding, enjoyment and engagement in VMAT planning. While technical issues affected session efficiency, feedback supports the integration of gamification in treatment planning sessions but should not be overused as its usefulness can wear off.

This is a radiobiological modelling study aimed at comparing stereotactic ablative body radiotherapy (SABR) with conventional palliative radiotherapy (CPRT) and curative-dose volumetric-modulated arc therapy (CD-VMAT) in the palliation of patients with previously untreated head and neck cancer.

Three radiotherapy plans were generated for 8 patients with head and neck cancer: SABR, prescribed to 45 Gy in 5 fractions; CPRT, prescribed to 30 Gy in 5 fractions and CD-VMAT, prescribed to 70 Gy in 35 fractions. The tumour control probability (TCP) and normal tissue complication probability for salivary and swallowing function (NTCPsaliva and NTCPswallow, respectively) were determined. From those values, the therapeutic ratio, as measured by the uncomplicated tumour control probability (UTCP), was determined.

Dosimetric objectives were achieved in all treatment plans. SABR had a higher mean TCP compared to CPRT and CD-VMAT (100% vs 81% vs 93%, p = 0·003). There were no statistically significant differences in the mean NTCPs for salivary or swallowing function (mean NTCPsaliva 27% vs 41% vs 36%, p = 0·093 and mean NTCPswallow 9% vs 12% vs 23%, p = 0·093). This resulted in the mean UTCP being statistically significantly higher for SABR plans compared to CPRT and CD-VMAT (66% vs 42% vs 49%, p = 0·004).

It is feasible to create SABR plans that satisfy the dosimetric objectives in this study. Based on radiobiological modelling, SABR has superior TCP and similar NTCP, leading to a better therapeutic ratio than CPRT and CD-VMAT.

Adult medulloblastoma is a rare entity with a predilection for the development of radiation-induced malignant glioma (RIMG). Management of RIMG in the setting of prior craniospinal irradiation is a challenging scenario.

We report a case of a 51-year-old male with short-interval development of multicentric malignant glioma with MET mutation who previously underwent craniospinal radiation for adult medulloblastoma. Due to radiographic findings, linear accelerator (LINAC)-based fractionated stereotactic/IMRT was delivered to the right temporal lesion alongside systemic therapy. The patient had interval development of an IDH wildtype, high-grade left cerebellar glioma and underwent surgical resection and subsequent gamma knife stereotactic radiosurgery (GKRS) to the cavity.

GKRS targeting the surgical cavity was delivered with a fractionated regimen of 27 Gy in 3 fractions to the margin. One year after completion of GKRS, the patient had not developed any symptomatic radiation necrosis or neuroimaging changes reflective of treatment toxicity. In this patient, GKRS to minimise the integral dose exposure of normal tissues surrounding the target volume proved to be particularly advantageous in the setting of prior craniospinal irradiation.

RIMG poses significant challenges for radiation oncologists, particularly in the reirradiation setting. Decision-making involving multidisciplinary input balanced the necessity of dose escalation achieved by GKRS, while minimising the cumulative dose in the setting of prior craniospinal irradiation.

This report investigates excess frame count during radiotherapy sessions using Elekta Versa HD systems with X-ray Volume Imaging (XVI) technology at Singleton Hospital. The hospital has 4 clinical linear accelerators (linacs) with XVI, which were analysed to identity variations in the number of excess frames between machines and imaging protocols. Such deviations could affect imaging dose accuracy, patient safety, and system efficiency.

XVI log files were gathered from each linac over an 18-month period using data backups. A Python script was created to read and link all the required data in a simple format to generate histograms and tables.

The excessive frames resulted in increased radiation doses. Although individual doses were negligible, the highest excess dose for a single patient was 0.7 mSv in 1 fraction, leading to a total dose of 3.4 mSv instead of the expected 2.7 mSv scans which is equivalent to 3 months of background radiation extra. The study revealed that 1.7 % of all imaging sessions were affected (417 imaging fractions). It was identified that the ‘Fast’ Breast imaging protocols were more likely to generate excess frames, likely to be due to the increased gantry speed.

Despite the small individual doses, the findings raise concerns about system performance and patient safety for imaging, emphasising the need for further investigation to ensure optimal treatment accuracy and compliance with the Ionising Radiation (Medical Exposure) (Amendment) 2024), Regulation 11 and 12.

AI-based autocontouring products claim to be able to segment organs with accuracy comparable to humans. We compare the geometric and dosimetric performance of three AI-based autocontouring packages (Autocontour 2.5.6, (“RF”); Annotate 2.3.1, (“TP”) and RT-Mind_AI 1.0, (“MM”)) in the head and neck region.

We generated 14 organ at risk (OAR) autocontours on 13 computed tomography (CT) image sets. They were compared with clinical (human-generated) contours. The geometric differences were quantified by calculating Dice coefficients and Hausdorff distances. The autocontours were compared visually with the clinical controus by an expert physician. The autocontour sets were also ranked for accuracy by two physicians. The dosimetric effects were evaluated by recalculating treatment plans on the autocontoured CT sets.

RF and TP slightly outperformed MM in geometric metrics (the percentage of OARs having mean Dice coefficients > 0.7 was RF 57.1 %, TP 64.3 % and MM 50.0%). The physician judged RF and TP contours to be more anatomically accurate, on average, than the manual contours (manual contour mean accuracy score 2.49, RF 2.28, MM 3.24, TP 1.93). The mean scores given to the autocontours by the two physicians were better for RF and TP, compared to MM (RF 1.86, MM 2.36, TP 1.77). The dosimetric differences were similar for all three programs and were not strongly correlated with the geometric differences.

The performance of the three autocontouring packages in the head and neck region is similar, with TP and RF slightly outperforming MM. The correlation between geometric and dosimetric metrics is not strong, and dosimetric evaluation is therefore recommended before clinical use of autocontouring software.

Pelvic radiotherapy can be an important management option for people diagnosed with colorectal or anal cancer, who often experience a wide range of adverse effects that can be detrimental to Quality-of-Life (QoL) due to the radiotherapy. Clinical nurse specialists (CNS) are valuable multi-disciplinary members who provide a range of practical and holistic support to these patients, via on-treatment review appointments. A lack of evidence exists relating to colorectal and anal cancer patients’ perceptions of on-treatment CNS review appointments.

A service evaluation of the nurse-led on-treatment appointments using a questionnaire was undertaken. Yes/No, Likert Scale and free-text questions were asked, allowing for quantitative and qualitative data collection. Ethical approval was obtained. Standard quantitative data analysis and thematic analysis (TA) methods were used.

Twelve [12] colorectal and anal cancer patients participated. The data showed that patients had positive experiences with their appointments, but had fears regarding the unknown and the future.

Patients were satisfied with the on-treatment review service, and the results suggest that the service is efficient and effective. Future research should evaluate this type of colorectal CNS service across a larger colorectal and anal cancer patient population.

Few breast cancer radiotherapy studies include either patients with a hearing impairment or non-English speakers. Literature about healthcare and cancer care in general provided insights into reports by patients of disparities. Given technological advancements, it is reasonable to believe communication barriers should be surmountable, prompting a survey of radiotherapy departments to assess the status quo.

A survey was conducted of all UK National Health Service (NHS) radiotherapy departments in England. A questionnaire was designed to determine if a deep inspiration breath hold (DIBH) technique was used for breast cancer radiotherapy, the equipment that was used and whether patients with a hearing impairment or other language barriers received the same treatment.

A total of 22 radiotherapy departments responded to the survey. All respondents reported using DIBH as a heart-sparing technique; 100% (n = 22) reported offering DIBH to non-English speakers and 73% (n = 16) DIBH to patients with a hearing impairment. 45% (n = 10) stated that they use verbal instruction only, and 23% (n = 5) a combination of both verbal and visual aids and references.

The study highlights some novel efforts in radiotherapy departments to increase equitable access to DIBH; however, the results indicate that verbal communication methods still dominate practice, and these are not inclusive of all hearing-impaired patients. Such methods would also require translation for non-English speakers. The study suggests that more work needs to be done before equitable access is achieved for patients with a hearing impairment or other language barrier.

For any patient’s cancer journey, effective communication and helpful information are key to staying informed and reducing anxiety; for radiotherapy, ideally before treatment commencement. This paper details the initial design and service evaluation of a virtual tour (VT) aimed at familiarising patients with the department before treatment starts.

Created by local digital science students, with input from hospital Patient Public Involvement groups, patients were recruited (after their initial planning visit) into non-VT and VT groups; the latter viewing the VT before their first treatment. Both groups completed identical online surveys with Likert-style questions and free-text entry to assess knowledge and understanding.

Twenty-three completed survey responses were received: 9 and 14 from the non-VT and VT groups, respectively.

• • 66.7% of the non-VT group felt anxious attending the department for the first time; compared with 28.6% in the VT group. Key comments included ‘not now that I’ve seen the video’

• • 92.9% of the VT group understood the queue calling and changing room systems compared with 55.6% in the non-VT group.

• • 85.7% of the VT group knew what to expect in the treatment room, compared to 33.3% in the non-VT group. Key comments included ‘the video helped’.

Other comments included ‘excellent idea’ and ‘alleviates the concerns about where to go and what to expect ahead of that first visit’.

The implementation of the VT has proved beneficial to patients, providing key information prior to treatment start, alleviating concerns and resulting in improved patient experience without the need for an extra visit.

Prolonged overall treatment time (OTT) in radiotherapy (RT) for head and neck cancer (HNC), particularly beyond 49 days, has been linked to poorer tumour control and survival, primarily due to accelerated tumour repopulation. Identifying modifiable factors contributing to treatment delays may help improve outcomes. This study aimed to evaluate the association between pre-treatment clinical, nutritional and inflammatory factors and prolonged OTT.

We retrospectively analysed patients with non-metastatic HNC treated with definitive or postoperative RT (with or without chemotherapy) between 2020 and 2022. Pre-treatment factors included Eastern Cooperative Oncology Group (ECOG) performance status, tumour stage, treatment modality, body mass index (BMI), weight loss, sarcopenia (via C3 computed tomography imaging), neutrophil-to-lymphocyte ratio (NLR) and absolute lymphocyte count. Logistic regression was used to identify predictors of prolonged OTT (> 49 days).

Among 465 patients, 287 (61·7%) experienced prolonged OTT. Multivariable analysis identified ECOG status (OR 1·42, p = 0·004), significant weight loss > 5% (OR 1·26, p = 0·036), concurrent chemotherapy (OR 1·96, p = 0·005), NLR (OR 1·03, p = 0·041) and sarcopenia (OR 1·18, p = 0·042) as independent predictors. Patient-related delays accounted for 53·3% of OTT prolongation, while public holidays contributed to 42·5%.

Several modifiable pre-treatment factors—including poor performance status, pre-treatment weight loss, sarcopenia and systemic inflammation—were independently associated with OTT prolongation. These findings provide evidence to support early, patient-tailored interventions such as prehabilitation and intensive nutritional counselling before and during RT. In addition, system-level strategies, including staffing adjustments and compensatory scheduling during public holidays, may further reduce avoidable treatment delays and enhance care delivery.

An evaluation was conducted for HyperArc brain stereotactic radiosurgery (SRS) plans to determine the effect of intra-fractional motion on target coverage and dosimetry to understand the safe limits of zero-PTV-margin HyperArc SRS treatments.

The Steve phantom was CT scanned with an Encompass mask and imported into the Eclipse Treatment Planning System, version 16·01. Two high-resolution spherical contours (GTV1 and GTV2) were generated with various sizes and separations. The rotational shift was transformed into translation based on the distance from the tumours to the isocentre and the rotational angle between the tumours. The effect of translational shifts corresponding to each rotational shift on dosimetric performance was evaluated for various tumour sizes and distances to the isocentre.

The tumour coverage was compared for different tumour sizes and distances to the isocentre due to intra-fractional motion. For tumour sizes less than 6 mm in diameter, the volume coverage changes significantly for separations greater than 5·5 cm from the isocentre. The effects of intra-fractional motion on dosimetry dominate for separations greater than 5·5 cm. Even though the percent volume coverage changes sharply for extreme shifts, the percent dose coverage stays between 70 and 80% for extreme shifts (1·2° in our case) for all lesion sizes.

The target-to-isocentre separation and the size of the lesions are two major factors that contribute to significant dosimetric deviations. When the target-to-isocentre distance is within 3·5 cm, D100% is over 90% coverage. Over 90% target coverage is achievable for zero PTV margin in situations where extreme shifts of 1·2° exist.

This study aimed to report the outcomes of patient-specific quality assurance (QA) in spot-scanning proton therapy using a two-dimensional ionisation chamber array and investigate the relationship between gamma passing rate and plan parameters.

Patient-specific QA was performed and evaluated by gamma analysis using a 3% dose difference and 2-mm distance-to-agreement with 172 treatment plans in the head and neck, breast, chest, abdominal and pelvic regions. The outcomes of patient-specific quality assurance regarding the gamma passing rate of the treatment sites, monitor unit (MU) per spot, measurement depth, range shifter, number of spots, energy layer and target volume were analysed.

No significant difference (p = 0·10) in the gamma passing rates between the treatment sites. The gamma passing rate was >98% in all the regions. The overall result of patient-specific QA with the gamma evaluation was 99·1 ± 1·6%. For the MU per spot, range shifter and measurement depth, the gamma passing rate was >98%. The gamma passing rate of the number of spots, energy layer and target volume was >97%.

Patient-specific QA measurements showed that the gamma passing rate was >98% and was independent of the treatment site, MU per spot, range shifter, number of spots, energy layer and target volume but depend on measurement depth (p < 0·05). A gamma index of 3%, 2 mm forms reasonable criteria for patient-specific QA in spot-scanning proton therapy.