Dosimetric impact of rotational setup errors in volumetric modulated arc therapy for postoperative cervical cancer

Optimal Correction Strategy of Image Guided Radiation Therapy Including the Paraortic Lymph Node Region in Patients With Cervical Cancers

Purpose

The clinically accepted planning target volume margin for radiation therapy to the paraortic nodal region in cervical cancer patients is 5 mm. However, the comprehensive alignment and variability from the pelvic bone to all lumbar vertebrae are undetermined. This study aims to quantify the residual setup errors between the pelvic bone and lumbar vertebrae and determine the optimal correction strategy for patients with cervical cancer.

Materials and Methods

Fifteen patients underwent pretreatment mega-voltage computed tomography scans (375 total fractions). Residual setup errors and required margins for each lumbar vertebra were calculated based on registrations accounting for pelvic rotation and translation.

Results

The systematic residual errors (1 SD) at L1, L2, L3, L4, and L5 using pelvic bone registration were 6.5, 4.9, 3.1, 1.5, and 0.6 mm in the anterior-posterior (AP) direction, 3.1, 2.3, 1.4, 0.6, and 0.3 mm in the right-left direction, and 2.7, 2.2, 1.7, 1.0, and 0.5 mm in the superior-inferior direction, respectively. The residual setup errors were the largest in the AP direction. Registration based on the pelvic bone required margins in the AP direction of 16.0, 12.1, 7.7, 3.6, and 1.3 mm for L1, L2, L3, L4, and L5, respectively, whereas registration based on L3 required margins of 8.8, 4.8, 4.4, 7.1, and 7.7 mm for L1, L2, L4, L5, and pelvic bone, respectively.

Conclusions

Considerable local setup variability was found in patients with cervical cancer. After reviewing the corrective strategies, we determined that L3-based registration effectively minimized the required margins.

Preliminary study of feasibility of surface-guided radiotherapy with concurrent tumor treating fields for glioblastoma: region of interest

OBJECTIVE

To evaluate the impact of the residual setup errors from differently shaped region of interest (ROI) and investigate if surface-guided setup can be used in radiotherapy with concurrent tumor treating fields (TTFields) for glioblastoma.

METHODS

Fifteen patients undergone glioblastoma radiotherapy with concurrent TTFields were involved. Firstly, four shapes of region of interest (ROI) (strip-shaped, T-shaped, ⊥ -shaped and cross-shaped) with medium size relative to the whole face were defined dedicate for patients wearing TTFields transducer arrays. Then, ROI-shape-dependent residual setup errors in six degrees were evaluated using an anthropomorphic head and neck phantom taking CBCT data as reference. Finally, the four types of residual setup errors were converted into corresponding dosimetry deviations (including the target coverage and the organ at risk sparing) of the fifteen radiotherapy plans using a feasible and robust geometric-transform-based method.

RESULTS

The algebraic sum of the average residual setup errors in six degrees (mm in translational directions and ° in rotational directions) of the four types were 6.9, 1.1, 4.1 and 3.5 respectively. In terms of the ROI-shape-dependent dosimetry deviations, the D98% of PTV dropped off by (3.4 ± 2.0)% (p < 0.05), (0.3 ± 0.5)% (p < 0.05), (0.9 ± 0.9)% (p < 0.05) and (1.1 ± 0.8)% (p < 0.05). The D98% of CTV dropped off by (0.5 ± 0.6)% (p < 0.05) for the strip-shaped ROI while remained unchanged for others.

CONCLUSION

Surface-guided setup is feasible in radiotherapy with concurrent TTFields and a medium-sized T-shaped ROI is appropriate for the surface-based guidance.

Effect of body contour changes on the setup and dosimetric accuracy of radiotherapy after cervical cancer surgery

Purpose

The body contour of patients with cervical cancer is prone to change between radiotherapy sessions. This study aimed to investigate the effect of body contour changes on the setup and dosimetric accuracy of radiotherapy.

Methods

15 patients with cervical cancer after surgery were randomly selected for retrospective analysis. The body contours on the once-per-week cone-beam computed tomography (CBCT) were registered to the planning CT (pCT) for subsequent evaluation. A body contour conformity index (CIbody) was defined to quantify the variation of body changes. The body volume measured by CBCT was collected, and its relative difference in reference with the first CBCT was calculated and denoted by ΔVn. The relative setup errors, denoted by ΔSELR, ΔSEAP, ΔSESI, and ΔSEvec for left-right, anterior-posterior, superior-inferior, and vectorial shifts, respectively, were defined as the difference in measured setup errors between the reference and following CBCTs. The planned dose was calculated on the basis of virtual CT generated from CBCT and pCT by altering the CT body contour to fit the body on CBCT without deformable registration. The correlations between body contour changes and relative setup errors as well as dosimetric parameters were evaluated using Spearman's correlation coefficient rs .

Results

CIbody was found to be negatively correlated with the superior-inferior and vectorial relative setup errors ΔSESI (rs = -0.448, p = 0.001) and ΔSEvec (rs = -0.387, p = 0.002), and no significant correlation was found between relative setup errors and ΔVn. Moreover, ΔVn was negatively correlated with ΔD2 (rs = -0.829, p < 0.001), ΔD98 (rs = -0.797, p < 0.001), and ΔTVPIV (rs = -0.819, p < 0.001). ΔD2, ΔD98, and ΔTVPIV were negatively correlated with ΔVn (p < 0.005). No correlation was found for other examined dosimetric parameters.

Conclusion

The body contour change of patients could be associated with the setup variability. The effect of body contour changes on dose distribution is minimal. The extent of body change could be used as a metric for radiation therapists to estimate the setup errors.

The Prediction of Stress in Radiation Therapy: Integrating Artificial Intelligence with Biological Signals

This study aimed to predict stress in patients using artificial intelligence (AI) from biological signals and verify the effect of stress on respiratory irregularity. We measured 123 cases in 41 patients and calculated stress scores with seven stress-related features derived from heart-rate variability. The distribution and trends of stress scores across the treatment period were analyzed. Before-treatment information was used to predict the stress features during treatment. AI models included both non-pretrained (decision tree, random forest, support vector machine, long short-term memory (LSTM), and transformer) and pretrained (ChatGPT) models. Performance was evaluated using 10-fold cross-validation, exact match ratio, accuracy, recall, precision, and F1 score. Respiratory irregularities were calculated in phase and amplitude and analyzed for correlation with stress score. Over 90% of the patients experienced stress during radiation therapy. LSTM and prompt engineering GPT4.0 had the highest accuracy (feature classification, LSTM: 0.703, GPT4.0: 0.659; stress classification, LSTM: 0.846, GPT4.0: 0.769). A 10% increase in stress score was associated with a 0.286 higher phase irregularity (p < 0.025). Our research pioneers the use of AI and biological signals for stress prediction in patients undergoing radiation therapy, potentially identifying those needing psychological support and suggesting methods to improve radiotherapy effectiveness through stress management.

Evaluation of a head rest prototype for rotational corrections in three degrees of freedom

Cranial stereotactic irradiations require accurate reproduction of the planning CT patient position at the time of treatment, including removal of rotational offsets. A device prototype was evaluated for potential clinical use to correct rotational positional offsets in image-guided radiotherapy workflow. Analysis was carried out with a prototype device "RPS head" by gKteso GmbH, rotatable up to 4° in three dimensions by hand wheels. A software tool accounts for the nonrectangular rotation axes and also indicates translational motions to be performed with the standard couch to correct the initial offset and translational shifts introduced by the rotational motion. The accuracy of angular corrections and positioning of an Alderson RANDO head phantom using the prototype device was evaluated for nine treatment plans for cranial targets. Corrections were obtained from cone beam computed tomography (CBCT) imaging. The phantom position was adjusted and the final position was then verified by another CBCT. The long-term stability of the prototype device was evaluated. Attenuation by the device along its three main axes was assessed. A planning study was performed to evaluate if regions of high-density material can be avoided during plan generation. The device enabled the accurate correction of rotational offsets in a clinical setup with a mean residual angular difference of (0.0 ± 0.1)° and a maximum deviation of 0.2°. Translational offsets were less than 1 mm. The device was stable over a period of 20 min, not changing the head support plate position by more than (0.7 ± 0.6) mm. The device contains high-density material in the adjustment mechanism and slightly higher density in the support structures. These can be avoided during planning generation maintaining comparable plan quality. The head positioning device can be used to correct rotational offsets in a clinical setting.

Concurrent chemoradiotherapy followed by adjuvant chemotherapy versus concurrent chemoradiotherapy alone in locally advanced cervical cancer: A systematic review and meta-analysis

Objective

This study aimed to assess the efficacy and safety of adjuvant chemotherapy (ACT) after concurrent chemoradiation (CCRT) in patients with locally advanced cervical cancer (LACC) via meta-analysis.

Methods

A systematic literature search of MEDLINE, PubMed, Web of Science, EMBASE, and the Cochrane Central Register of Controlled Trials was conducted from January 10, 1966 to May 20, 2022. Randomized controlled trials and observational studies comparing the CCRT alone with CCRT plus ACT were included. The literature search, quality assessment, and data extraction were conducted by two reviewers independently. The primary endpoints were 3-year rates of overall survival (OS) and progression-free survival (PFS). Complete response rate, local recurrence, distant metastasis, and adverse events were secondary outcomes. The hazard ratios (HRs) and relative risk (RR) were pooled.

Results

Nine studies with a total of 2732 patients were included in this meta-analysis, including 1411 patients in the CCRT group and 1321 in the CCRT plus ACT group. The HR for 3-year rates of OS and PFS of the CCRT group compared with the CCRT plus ACT group was 0.72 [95%confidence interval (CI) = 0.44-1.17] and 0.78 (95%CI = 0.5-1.75), respectively. No significant differences were observed between the two groups in the complete response rate (RR = 1.06, 95%CI = 0.96-1.16). However, local recurrence and distant metastasis were significantly lower in the CCRT plus ACT group than in the CCRT group (RR = 0.63, 95%CI = 0.44 -0.91 and RR = 0.64, 95%CI = 0.47-0.88). Grade 3-4 acute toxicities were more frequent in the CCRT plus ACT group (RR = 1.73, 95%CI =1.19-2.52).

Conclusion

Although associated with a decreased risk of local recurrence and distant metastasis, ACT did not significantly improve the survival rate and the complete response rate with increasing grade 3-4 acute toxicities in patients with LACC. Thus, this ACT regimen cannot be recommended for patients with LACC.

Systematic review registration

https://inplasy.com/inplasy-2022-9-0089/, identifier INPLASY202290089.

Dosimetric impacts of cone-beam computed tomography (CBCT)-based anatomic changes in intensity-modulated radiotherapy for cervical cancer

Background

To evaluate the effects of dose to tumors and organs at risk (OARs) on inter-fractional anatomic changes.

Methods

We evaluated nine patients with cervical cancer treated with intensity-modulated radiotherapy (IMRT) (45 Gy in 25 fractions) using kV cone-beam computed tomography (CBCT) image guidance once or twice a week before treatment. For each patient, the original plan on the computed tomography (CT) image was copied to merged images, and then the fractional doses were calculated. Subsequently, deformable accumulated doses were obtained by summing the fractional absolute doses into a single dose in MIM Maestro software. The volume changes in the target and OARs were compared between the original CT and merged CBCT images, and the differences in the fractional and accumulated doses were also evaluated.

Results

Sixty-nine merged CBCT images were obtained and analyzed in this study. For the target areas, the volume changes in the clinical target volume (CTV) and planning target volume (PTV) reached -18.05% and -24.11% at most, respectively. The fractional D_2% of the CTV and PTV was generally higher than the original plans, and the accumulated deviations were 2.27%±0.82% (P<0.01) and 2.42%±1.28% (P<0.01), respectively. The fractional D_98% of the PTV was underdosed up to 18.28% for 78% of patients, and the accumulated deviations were -2.06% to -17.29% (P<0.05). For the OARs, the bladder volume changes were the most dramatic, reducing up to 93.60%. The fractional Dmean and D_2cc of the bladder were generally higher than the original plans, and there were significant differences in their accumulated values (P<0.05). There was no obvious trend of rectal volume change with -69.65% to 74.20%. The rectum D_mean and D_2cc of the accumulated were not significantly different from the planned dose (P>0.05).

Conclusions

For patients with cervical cancer, the changes in bladder and rectal volume were greater than in the target volume. Although the volume changes in the bladder and rectum had no significant effect on D_98% of the CTV and PTV, they had a significant effect on their own D_2cc and the D_2% of the CTV and PTV. More attention should be paid to the volume changes in the bladder and rectum in clinical work.

Real-world clinical outcomes with daily image-guided IMRT in extremity soft tissue sarcomas

PURPOSE

We report the clinical outcomes of patients with soft tissue sarcomas (STS) arising in extremities treated with image-guided intensity modulated radiotherapy (IG-IMRT) at our institute. Local control of the tumors treated with RT was the primary end point of this study. Analyzing overall survival and long-term toxicities were the secondary objectives.

METHODS AND MATERIALS

The database of the patients with STS who received wide local excision and IG-IMRT at our institution from January 2012 to December 2020 was reviewed. Radiation was offered either preoperatively or postoperatively as part of multi-modality treatment.

RESULTS

Thirty-three consecutive patients were identified and included for analysis. Twenty-eight patients (84.8%) received postoperative adjuvant radiotherapy. Dedicated MRI simulation studies were performed in 31 patients (93.9%) in the treatment position. RapidArc IMRT technique was used in 31 patients (93.9%). A total of 2954 images were acquired during 991 treatment sessions. Errors exceeding 1 mm in the x, y and z directions were corrected online before the treatment. With a median follow-up of 36 months, two patients (6.1%) developed local recurrence. The 3-year local control was 90.9% (95% CI, 0.76 - 0.98), and the 5-year overall survival was 71.7% (95% CI, 0.44 - 0.88). One patient (3.03%) sustained a pathological fracture during the follow-up period.

CONCLUSION

Our results showed that IMRT with daily imaging offered excellent local control with acceptable long-term toxicity, as well as being feasible and practical to implement in our routine clinical practice.

Dose Prediction Models Based on Geometric and Plan Optimization Parameter for Adjuvant Radiotherapy Planning Design in Cervical Cancer Radiotherapy

The prediction of an additional space for the dose sparing of organs at risk (OAR) in radiotherapy is still difficult. In this pursuit, the present study was envisaged to find out the factors affecting the bladder and rectum dosimetry of cervical cancer. Additionally, the relationship between the dose-volume histogram (DVH) parameters and the geometry and plan dose-volume optimization parameters of the bladder/rectum was established to develop the dose prediction models and guide the planning design for lower OARs dose coverage directly. Thirty volume modulated radiation therapy (VMAT) plans from cervical cancer patients were randomly chosen to build the dose prediction models. The target dose coverage was evaluated. Dose prediction models were established by univariate and multiple linear regression among the dosimetric parameters of the bladder/rectum, the geometry parameters (planning target volume (PTV), volume of bladder/rectum, overlap volume of bladder/rectum (OV), and overlapped volume as a percentage of bladder/rectum volume (OP)), and corresponding plan dose-volume optimization parameters of the nonoverlapping structures (the structure of bladder/rectum outside the PTV (NOS)). Finally, the accuracy of the prediction models was evaluated by tracking d = (predicted dose-actual dose)/actual in additional ten VMAT plans. V ₃₀, V ₃₅, and V ₄₀ of the bladder and rectum were found to be multiple linearly correlated with the relevant OP and corresponding dose-volume optimization parameters of NOS (regression R ² > 0.99, P < 0.001). The variations of these models were less than 0.5% for bladder and rectum. Percentage of bladder and rectum within the PTV and the dose-volume optimization parameters of NOS could be used to predict the dose quantitatively. The parameters of NOS as a limited condition could be used in the plan optimization instead of limiting the dose and volume of the entire OAR traditionally, which made the plan optimization more unified and convenient and strengthened the plan quality and consistency.