Dosimetric effects of weight loss or gain during volumetric modulated arc therapy and intensity-modulated radiation therapy for prostate cancer

Life style and interaction with microbiota in prostate cancer patients undergoing radiotherapy: study protocol for a randomized controlled trial

Background

Prostate cancer (PCa) is the second most common cancer in men worldwide. The standard non-surgical approach for localized PCa is radiotherapy (RT), but one of the limitations of high-dose RT is the potential increase in gastrointestinal and genitourinary toxicities. We present the protocol of the Microstyle study, a multicentre randomized two-arm crossover clinical trial. The primary outcome will be assessed at the end of 6-month intervention, by measuring the change in adherence to a healthy lifestyle score. The hypothesis is that modifying lifestyle we change microbiome and improve quality of life and decrease side effects of RT.

Methods

Study participants will be recruited among men undergoing RT in two Italian centers (Milan and Naples). We foresee to randomize 300 patients in two intervention arms: Intervention Group (IG) and Control Group (CG). Participants allocated to the IG will meet a dietitian and a physiotherapist before RT to receive personalized diet and exercise recommendations, according to their health status, to improve overall lifestyle and reduce side effects (bowel and/or urinary problems). Dietitian and physiotherapist will work together to set individualized goals to reduce or eliminate side effects and pain according to their health status. All participants (IG) will be given a pedometer device (steps counter) in order to monitor and to spur participants to increase physical activity and reduce sedentary behavior. Participants included in the CG will receive baseline general advice and materials available for patients undergoing RT. According to the cross-over design, the CG will cross to the intervention approach after 6-month, to actively enhance compliance towards suggested lifestyle recommendations for all patients.

Discussion

This trial is innovative in its design because we propose a lifestyle intervention during RT, that includes both dietary and physical activity counselling, as well as monitoring changes in microbiome and serum biomarkers. The promotion of healthy behaviour will be initiated before initiation of standard care, to achieve long lasting effects, controlling side effects, coping with feelings of anxiety and depression and improve efficacy of RT.

Trial registration

ClincalTrial.gov registration number: NCT05155618. Retrospectively registered on December 13, 2021. The first patient was enrolled on October 22, 2021.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09521-4.

Use of specific duodenal dose constraints during treatment planning reduces toxicity after definitive para-aortic radiotherapy for cervical cancer

PURPOSE

To validate the safety of paraaortic nodal (PAN) radiation therapy (RT) for patients with cervical cancer when the duodenal dose is limited to V₅₅<15 cm³ and V₆₀<2 cm³.

METHODS AND MATERIALS

Ninety-seven patients who were treated with RT for cervical cancer between 2010 and 2018, received at least 56 Gy to grossly involved PANs. Patients were treated with concurrent chemoradiation (n=88, 91%), with 93% (n=90) receiving intensity-modulated RT (IMRT) to the initial PAN field, and 98% (n=95) receiving IMRT to a sequential PAN boost. V₅₅<15 cm³ and V₆₀ <2 cm³ criteria were implemented in 2014. Normal tissues were contoured on CT simulation datasets; the duodenum was contoured from the gastric outlet to the duodenojejunal flexure. Sixty-six patients (68%) had a resimulation scan after approximately 20 fractions. Composite duodenal doses were calculated using the initial CT for 50 patients (52%) and the resimulation CT for 47 patients (48%) depending on anatomic changes throughout treatment.

RESULTS

The median duodenal V₅₅ was 3.5 cm³ (interquartile range [IQR] 0.2-8.1 cm³) and the median V₆₀ was 0.3 cm³ (IQR 0.0-1.8). Constraints were exceeded in 18 patients, 16 (89%) of whom had been treated before 2014. Treatment for the 2 patients treated after 2014 had been complicated by significant weight loss and reduced anterior-posterior diameter, which likely overestimated the true dose on the composite plan. Only 1 patient experienced grade 3 duodenal toxicity (stricture requiring endoscopic balloon dilation 3 months after treatment); however, the stricture was outside the high-dose boost volume and the patient had a history of gastritis. Six patients (6%) had a first recurrence within the PAN region.

CONCLUSIONS

Limiting duodenal dose to V₅₅<15 cm³ and V₆₀<2 cm³ for patients with cervical cancer and PAN involvement is feasible and minimizes duodenal toxicity while maintaining acceptable local control rates.

The effect of nutritional interventions involving dietary counselling on gastrointestinal toxicities in adults receiving pelvic radiotherapy - A systematic review

Gastrointestinal (GI) toxicities are common in patients receiving radiotherapy (RT) to the pelvis. This systematic review aims to evaluate the effectiveness of nutritional interventions involving dietary counselling (DC) on GI toxicities in patients receiving pelvic RT. The search method entailed two phases to retrieve studies. Articles from a previous Cochrane review by Lawrie et al. 2018 were assessed for inclusion. An updated systematic search was then conducted to retrieve articles published between 2013 and 2020 from five electronic databases (MEDLINE, EMBASE, CINAHL, CENTRAL and Scopus). The inclusion criteria entailed randomised controlled trials involving adults ≥18 years, undergoing curative pelvic RT, receiving a nutritional intervention involving DC with or without supplements. DC was defined as written or face-to-face dietary advice provided before or during RT. Outcomes included GI toxicities reported by validated assessment tools. The Academy of Nutrition and Dietetics Quality Criteria Checklist was utilised to assess quality and risk of bias. Of 1922 studies retrieved, 12 articles encompassing 11 individual RCTs were included. Seven studies included a supplement in addition to DC. Supplements included probiotics, prebiotics, probiotic + soluble fibre, high protein liquid supplement and fat emulsion. Of the 11 studies, one involved individualised DC, and the remaining studies prescribed consumption or avoidance of fats, fibre, lactose, protein and FODMAP. The most common toxicities reported were diarrhoea (n = 11), pain/cramping (n = 9) and bloating/flatulence (n = 5). Three studies stated an improvement in diarrhoea incidence. Results varied between studies. Further quality studies are required to assess the effectiveness of DC, in particular individualised DC on GI toxicities in patients receiving pelvic RT.

Use ofin vivotransit portal images to detect gross inter-fraction patient geometry changes on an O-ring type linear accelerator for pelvis and head/neck patients

The purpose of this work was to investigate the use of the Varian Portal Dosimetry application in conjunction within vivomegavoltage portal images on a Varian Halcyon O-ring type linear accelerator as anin vivodosimetry constancy (IVDc) tool for pelvis and head/neck patients receiving VMAT treatments. Sensitivity testing was conducted on phantoms with varying thicknesses (0.2 cm-1.0 cm) using static and modulated fields. A cohort of 96 portal dose images across eight patients was then compared with PTV metrics derived from daily CBCT image based treatment plan re-calculations to determine whether the IVDc tool could detect gross inter-fraction anatomical changes. A final cohort of 315 portal dose images across 22 patients was then assessed to demonstrate the application of IVDc tool. The IVDc tool, using 2%/2 mm criteria, detected all phantom thickness changes of 1.0 cm, some phantom thickness changes of 0.5 cm, and no changes of 0.2 cm. For the cohort of 96 results, a IVDc passing criteria of 95% (2%, 2 mm) was able to identify all cases that had PTV metric changes of 2% or more. Using the IVDc tool on the cohort of 315 results, and the IVDc passing criteria of 95%, resulted in 74 IVDc failures. A simple, easy to implement, methodology has been presented that is capable of detecting gross inter-fraction changes in patient geometry on the Varian Halcyon O-ring linac linear accelerator.

Dosimetric variations for high-risk prostate cancer by VMAT plans due to patient’s weight changes

Purpose:

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.

Methods and materials:

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.

Results:

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.

Conclusions:

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.

Impact of the antifermentative diet during radiotherapy for prostate cancer in elderly, SÃO Paulo, Brazil

OBJECTIVE

Assess the impact of the antifermentative diet on the dietary intake and body composition of elderly prostate cancer patients in radiotherapy.

METHODS

Observational and prospective study involving 45 men aged 60 years or older, receiving radiotherapy for prostate cancer treatment. The dietary intake was assessed at four times during radiotherapy: onset (T_Pre), between the 11th and 16th day (T₁), between the 24th and 28th day (T₂), and on the last day (T_Last). The body composition was assessed before and on the last day of radiotherapy, by means of the body weight and height, mid-arm circumference, triceps and subscapular skin folds, phase angle, resistance, and reactance. The data were statistically treated, considering a 5% significance level.

RESULTS

The intake of energy, dietary fibers, and some nutrients decreased during the radiotherapy (p < 0.05). The intake of vitamins E, B1, B2, and folate, of the minerals calcium, magnesium, potassium, sodium, and phosphorus, and of the amino acid leucine dropped when the four assessment times were compared (p < 0.05). As regards the body composition, an impact was observed at the end of the radiotherapy, with lower body weight, arm circumference, subscapular cutaneous fold, phase angle and reactance (p < 0.05).

CONCLUSION

The antifermentative diet negatively influenced the food consumption and body composition of elderly patients submitted to radiotherapy for prostate cancer.

An evaluation of adaptive planning by assessing the dosimetric impact of weight loss throughout the course of radiotherapy in bilateral treatment of head and neck cancer patients

The purpose of this study was to investigate the dosimetric impact of weight loss in head and neck (H&N) patients and examine the effectiveness of adaptive planning. Data was collected from 22 H&N cancer patients who experienced weight loss during their course of radiotherapy. The robustness of Intensity Modulated Radiation Therapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT) treatment plans were compared including the potential need for replanning. The dosimetric impact of weight loss was evaluated by calculating a verification plan for each patient on an assessment CT scan taken during the course of treatment. Using a regression analysis, significance was tested for the dosimetric change in target volumes and 10 specific organs at risk (OAR) using an anatomical separation difference in the H&N at corresponding levels. For both the IMRT and VMAT plans, a significant correlation was found for the dose to 5% of the high risk Planning Target Volume (PTV) (D₅), dose to 95% of the intermediate risk PTV and Clinical Target Volume (CTV) (D₉₅), and the percentage of the pharynx receiving 65 Gy. An independent t-test was also performed for each metric in the VMAT and IMRT plans showing the dose to 95% of the intermediate risk PTV as significant. No quantitative method for finding the threshold of anatomical separation difference requiring a replan was established. Based on the increase in dose to organs at risk and increased target coverage due to separation loss, it was concluded that adaptive radiotherapy may not always be necessary when alignment of bony anatomy and remaining soft tissue is within tolerance. Physician judgment and preference is needed in such situations.

Effect of Changing Phantom Thickness on Helical Radiotherapy Plan: Dosimetric Analysis

Purpose: The aim of this study is to investigate the effect of changing phantom thickness on high dose region of interest (HD_ROI) and low dose ROI’s (LW_ROI’s) doses during helical radiotherapy (RT) by utilizing Adaptive RT (ART) technique.

Materials and Methods: The cylindrical phantom (CP) is wrapped with different thickness boluses and scanned in the kilovoltage computed tomography (KVCT). HD_ROI and LW_ROI’s were created in contouring system and nine same plans (1.8 Gy/Fr) were made with images of different thicknesses CP. The point dose measurements were performed using ionization chamber in Helical Tomotherapy (HT) treatment machine. For detecting thickness reduction effect, CP was irradiated using bolus-designed plans and it was irradiated using without bolus plan. The opposite of this scenario was applied to determine the thickness increase. KVCT and megavoltage CT (MVCT) images were used for dose comparison. The HT Planned Adaptive Software was used to see the differences in the planning and verification doses at dose volume histograms (DVH).

Results: Point dose measurements showed a 4.480% dose increase in 0.5 cm depth reduction for HD_ROI. These differences reached 8.508% in 2 cm depth and 15,279% in 5 cm depth. At the same time, a dose reduction of 0.665% was determined for a 0.5cm depth increase, a dose reduction of 1.771% was determined for a 2 cm depth increase, a dose reduction of 5.202% was determined for a 5 cm depth increase for the HD_ROI. The ART plan results show that the dose changes in the HD_ROI was greater than the LW_ROI’s.

Conclusion: Phantom thicknesses change can lead to a serious dose increase or decrease in the HD_ROI and LW_ROI’s.

Dosimetric effect of body contour changes for prostate and head and neck volumetric modulated arc therapy plans

Body contour changes are commonly seen in prostate and head and neck (H&N) patients undergoing volumetric modulated arc therapy (VMAT) treatments, which may cause a discrepancy between the planned dose and the delivered dose. Dosimetrists, radiation oncologists or medical physicists sometimes are required to visually assess the dosimetric impact of body contour changes and make a judgment call on whether further re‐assessment of the plan is needed. However, an intuitive judgment cannot always be made in a timely manner due to the complexity of VMAT plans as well as the complicated forms of body contour changes. This study evaluated the dosimetric effect of body contour changes for prostate and H&N patients to help with clinical decision‐making. By analyzing the one‐dimensional spatial dose profiles from the original body and the body with different body contour deformations, rules of thumb for dose percentage change and isodose line shift due to body contour changes were ascertained. Moreover, based on dose distribution comparison using three‐dimensional gamma analysis, the response of the clinical prostate and H&N VMAT plans to body contour changes was assessed. Within center specific dose deviation tolerances, prostate patients who had less than 2 cm single side body contour change or less than 1 cm uniform body contour change were unlikely to need plan re‐assessment; H&N VMAT plans with less than 1 cm uniform body contour change or less than 1 cm shoulder superior–inferior positional change were also unlikely to trigger further evaluation. Dose percentage change and isodose line shift were considered independently from the problem of volume changes in this study, but clinically, both aspects must be considered.

Avoidance sectors to reduce dosimetric impact of an irreproducible pannus on setup uncertainty in prostate SBRT VMAT: A case study

This work investigates whether the use of an avoidance sector in a two-arc volumetric modulated arc therapy (VMAT) prostate stereotactic body radiotherapy (SBRT) plan reduces dosimetric variations due to an irreproducible pannus. A morbidly obese patient with favorable-risk prostate cancer elected treatment with SBRT. The patient was treated with the avoidance arcs across the pannus to eliminate reproducibility issues created by daily pannus variability in set up. For post-treatment assessment, the case was planned using Varian Eclipse™ treatment planning system (TPS) with two VMAT arcs with and without 100° avoidance sectors across the pannus. The dose was re-calculated using the external body contour from four daily treatment cone-beam computer tomography scans, and on two virtual body contours created by expanding the pannus region of the external contour by 5 and 10 mm. Dose differences between planned and re-calculated rectal wall mean dose and the V_24Gy were numerically larger in the absence of the avoidance sector for all fractions and for both simulated pannus variations, with maximum changes of 2.6% and 1.3%. Maximum point dose variations in the PTV, CTV, rectum, bladder, and femoral heads were 105 cGy or less for all cases, with and without the avoidance sector. The use of an avoidance sector across this large, asymmetrical pannus did not inhibit achieving dose constraints and provided a reduction in dose variability which was nominal in this case for 10 mm variations. Avoidance sectors can be safely implemented in cases with obvious reproducibility concerns in the setting of prostate VMAT SBRT.

Dosimetric effects of anatomical changes during fractionated photon radiation therapy in pancreatic cancer patients

Pancreatic tumors show large interfractional position variation. In addition, changes in gastrointestinal gas volumes and body contour take place over the course of radiation therapy. We aimed to quantify the effect of these anatomical changes on target dose coverage, for the clinically used fiducial marker‐based patient position verification and, for comparison, also for simulated bony anatomy‐based position verification. Nine consecutive patients were included in this retrospective study. To enable fraction dose calculations on cone‐beam CT (CBCT), the planning CT was deformably registered to each CBCT (13–15 per patient); gas volumes visible on CBCT were copied to the deformed CT. Fraction doses were calculated for the clinically used 10 MV VMAT treatment plan (with for the planning target volume (PTV): D_98% = 95%), according to fiducial marker‐based and bony anatomy‐based image registrations. Dose distributions were rigidly summed to yield the accumulated dose. To evaluate target dose coverage, we defined an iCTV_{+5 mm} volume, i.e., the internal clinical target volume (iCTV) expanded with a 5 mm margin to account for remaining uncertainties including delineation uncertainties. We analyzed D_98%, D_mean, and D_2% for iCTV_{+5 mm} and PTV (i.e., iCTV plus 10 mm margin). We found that for fiducial marker‐based registration, differences between fraction doses and planned dose were minimal. For bony anatomy‐based registration, fraction doses differed considerably, resulting in large differences between planned and accumulated dose for some patients, up to a decrease in D_98% of the iCTV_{+5 mm} from 95.9% to 85.8%. Our study shows that fractionated photon irradiation of pancreatic tumors is robust against variations in body contour and gastrointestinal gas, with dose coverage only mildly affected. However, as a result of interfractional tumor position variations, target dose coverage can severely decline when using bony anatomy for patient position verification. Therefore, the use of intratumoral fiducial marker‐based daily position verification is essential in pancreatic cancer patients.

Use of auto-segmentation in the delineation of target volumes and organs at risk in head and neck

BACKGROUND

Manual delineation of structures in head and neck cancers is an extremely time-consuming and labor-intensive procedure. With centers worldwide moving towards the use of intensity-modulated radiotherapy and adaptive radiotherapy, there is a need to explore and analyze auto-segmentation (AS) software, in the search for a faster yet accurate method of structure delineation.

MATERIAL AND METHODS

A search for studies published after 2005 comparing AS and manual delineation in contouring organ at risks (OARs) and target volume for head and neck patients was conducted. The reviewed results were then categorized into arguments proposing and opposing the review title.

RESULTS

Ten studies were reviewed and derived results were assessed in terms of delineation time-saving ability and extent of delineation accuracy. The influence of other external factors (observer variability, AS strategies adopted and stage of disease) were also considered. Results were conflicting with some studies demonstrating great potential in replacing manual delineation whereas other studies illustrated otherwise. Six of 10 studies investigated time saving; the largest time saving reported being 59%. However, one study found that additional time of 15.7% was required for AS. Four studies reported AS contours to be between 'reasonably good' and 'better quality' than the clinically used contours. Remaining studies cited lack of contrast, AS strategy used and the need for physician intervention as limitations in the standardized use of AS.

DISCUSSION

The studies demonstrated significant potential of AS as a useful delineation tool in contouring target volumes and OARs in head and neck cancers. However, it is evident that AS cannot totally replace manual delineation in contouring some structures in the head and neck and cannot be used independently without human intervention. It is also emphasized that delineation studies should be conducted locally so as to evaluate the true value of AS in head and neck cancers in a specific center.