Dosimetric comparative study of 3 different postoperative radiotherapy techniques (3D-CRT, IMRT, and RapidArc) for II-III stage rectal cancer

Efficacy of the collapsed cone algorithm calculated radiotherapy plans in intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT): A comparative dosimetric study in tumors of thorax

AIM

In this study, efficacy of collapsed cone algorithm-generated intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) were evaluated for treatment of thoracic esophageal cancer.

MATERIALS AND METHODS

Ten previously treated patients with VMAT were considered for evaluation. The planning parameters were evaluated in terms of max dose, mean dose, Homogeneity Index, Conformity Index for planning target volume, and organ at risk doses. Total monitor unit, treatment time, and gamma passing index were also reported.

RESULTS

The target dose coverage of the VMAT and IMRT plans achieved the clinical dosimetric criteria for all ten patients in the evaluation. Under the condition of equivalent target dose distribution, the VMAT plan's Conformity Index, monitor unit, treatment time, and gamma passing index rate were superior than in the IMRT plan, and the result was statistically significant.

CONCLUSION

Collapsed cone algorithm-based VMAT can have a more effective and better approach for esophageal cancer than IMRT.

Advances in the management of radiation-induced cystitis in patients with pelvic malignancies

OBJECTIVE

Radiotherapy plays a vital role as a treatment for malignant pelvic tumors, in which the bladder represents a significant organ at risk involved during tumor radiotherapy. Exposing the bladder wall to high doses of ionizing radiation is unavoidable and will lead to radiation cystitis (RC) because of its central position in the pelvic cavity. Radiation cystitis will result in several complications (e.g. frequent micturition, urgent urination, and nocturia) that can significantly reduce the patient's quality of life and in very severe cases become life-threatening.

METHODS

Existing studies on the pathophysiology, prevention, and management of radiation-induced cystitis from January 1990 to December 2021 were reviewed. PubMed was used as the main search engine. Besides the reviewed studies, citations to those studies were also included.

RESULTS AND DISCUSSIONS

In this review, the symptoms of radiation cystitis and the mainstream grading scales employed in clinical situations are presented. Next, preclinical and clinical research on preventing and treating radiation cystitis are summarized, and an overview of currently available prevention and treatment strategies as guidelines for clinicians is provided. Treatment options involve symptomatic treatment, vascular interventional therapy, surgery, hyperbaric oxygen therapy (HBOT), bladder irrigation, and electrocoagulation. Prevention includes filling up the bladder to remove it from the radiation field and delivering radiation based on helical tomotherapy and CT-guided 3D intracavitary brachytherapy techniques.

Study on esophageal cancer radiotherapy dosimetry and position verification for volumetric modulated arc therapy

BACKGROUND

This study analyzed the respective advantages and disadvantages by comparing volumetric modulated arc therapy (VMAT) and intensity modulated radiotherapy (IMRT) on the dose distribution and position verification distribution characteristics in esophageal cancer radiotherapy, in order to provide the reference for the clinical radiotherapy technology optimization of esophageal cancer.

METHODS

A total of 56 cases of patients with esophageal cancer were selected and applied to the Pinnacle three-dimensional radiation treatment planning system (TPS), in order to design a VMAT plan and IMRT plan under the guidance of image-guided radiotherapy (IGRT). The dosimetry and position verification difference were compared between the two groups.

RESULTS

Revealed that the target dose distribution of the VMAT plan and IMRT plan meets the requirements in clinical dosimetry for all 56 patients in this study. Under the premise of similar target coverage, the conformal index (CI) of the VMAT plan, homogeneity index (HI), target volume, BODY-PTV radiated volume and spinal cord D_max, bilateral lung V5, V20 and mean lung dose (MLD), monitor unit (MU) and treatment time (TT), as well as position verification and others, were obviously superior to those in the IMRT plan; and the difference was statistically significant.

CONCLUSION

CBCT guided VMAT is a potential effective treatment for esophageal cancer and may be more effective and safer than IMRT.

Dosimetric comparison of organs at risk in 5 different radiotherapy plans in patients with preoperatively irradiated rectal cancer

BACKGROUND

Intensity-modulated radiotherapy (IMRT) is a widely used irradiation technique in rectal cancer patients. We aimed to compare 4 different IMRT plans with 3-dimensional conformal radiotherapy (3D-CRT) considering organs at risk (OARs) in patients with rectal carcinoma.

METHODS

This retrospective study included 27 rectal cancer patients who were irradiated preoperatively between January 2016 and December 2018. Five different plans (4-field 3D-CRT in 2 phases, 7-field IMRT in 2 phases, 9-field IMRT in 2 phases, 7-field simultaneous integrated boost [SIB] IMRT, and 9-field SIB IMRT) were generated for each patient. Comparison of 5 different plans according to bladder and bilateral femoral head mean doses, bladder V40, bilateral femoral head V40, and small bowel V35 values were evaluated.

RESULTS

Most of the OAR parameters significantly favored IMRT plans compared to the 3D-CRT plan. The largest difference was observed in bladder V40 values (reduction of V40 value up to 51.2% reduction) in favor of IMRT. In addition, SIB plans showed significantly better reduction in OARs than phase plans except for small bowel V35 values.

CONCLUSIONS

IMRT plans reduced almost all the OARs doses compared with the 3D-CRT plan in rectal cancer patients. Furthermore, SIB plans demonstrated lower OAR doses than the phase plans. IMRT techniques, especially SIB plans, reduce OAR doses and provide safer doses for the treatment of rectal carcinoma.

Effect of body thickness on helical and direct treatment delivery modes: a phantom study

Objective: Chemoradiation therapy is among the standard treatments for cancer, which often causes a decrease in appetite and subsequent weight loss. When weight loss occurs during treatment, the external body contour changes from that indicated during initial planning, causing changes in dose distribution to the target tumor regions and organs at risk (OARs). This study aimed to examine the dose changes to both the target regions and OARs, based on the dose-volume histogram (DVH).

Methods: We established a 60 mm-diameter planning target volume (PTV) and a 30 mm-diameter rectum region of interest (OAR), using a phantom; this was followed by a 50 Gy/25 fraction irradiation to the target region that was measured using a two-dimensional-array ion chamber device. The measurement was conducted by varying the bolus thickness from 0 to −25 mm, in 5 mm decrements. In addition, the maximum dose for both PTV and OAR were evaluated based on the DVH, created using the Adaptive software.

Results: The gamma analysis showed that the pass rate was less than 95% when the bolus thickness was altered by −25 mm for the helical delivery mode and by −10 mm for the direct delivery mode, resulting in a dose error greater than 3%. Results of the DVH evaluation revealed that the maximum dose of PTV increased by 5.18% when the bolus thickness was −25 mm for helical delivery, whereas a 9.95% increase was noted for the direct delivery mode compared with the dose at the reference level of 0 mm bolus thickness.

Discussion: Our results suggest that it is necessary to formulate a new treatment plan owing to increased dose error, if the body thickness decreases by more than 20 mm and 10 mm for the helical and direct delivery modes, respectively. The results also demonstrate that helical delivery is less affected by changes in body thickness than direct delivery.

Volumetric-modulated arc therapy versus intensity-modulated radiotherapy for large volume retroperitoneal sarcomas: A comparative analysis of dosimetric and treatment delivery parameters

Purpose

To compare dosimetric and treatment delivery parameter differences between volumetric‐modulated arc radiotherapy (VMAT) and intensity‐modulated radiotherapy (IMRT) for large volume retroperitoneal sarcomas (RPS).

Materials and Methods

Both VMAT and IMRT planning were performed on CT datasets of 10 patients with RPS who had been previously treated with preoperative radiotherapy. Plans were optimized to deliver ≥95% dose to the PTV and were evaluated for conformity and homogeneity. Dose to the organs at risk (OARs) (kidney, liver, spinal cord, and bowel space), unspecified tissue, and dose evaluation volumes (DEVs) at 1, 2, and 5 cm from PTV were calculated and compared. Monitor units (MUs) and treatment delivery times were recorded and compared between the two techniques. The deliverability of the large volume RPS VMAT plans was verified by portal dosimetry on a Truebeam™ linac.

Results

VMAT and IMRT plans were equivalent for PTV coverage and homogeneity (P > 0.05); however, VMAT plans had slightly better conformity index, CI (P < 0.001). Doses to the OARs were not significantly different between VMAT and IMRT plans (P > 0.05). Mean doses to the unspecified tissue as well as at 1, 2, and 5 cm DEVs were lower with VMAT compared with IMRT, P = 0.04 and P < 0.01, respectively. MUs and average beam‐on times were both significantly lower in the VMAT vs IMRT plans, P < 0.001 and P = 0.001, respectively. All VMAT plans passed portal dosimetry delivery verification with an average gamma passing rate of 99.6 ± 0.4%.

Conclusions

VMAT planning for large volume RPS improved CI, and achieved comparable OAR sparing, as compared with IMRT. As treatment delivery time was lower, the use of VMAT for RPS may translate into improved treatment delivery efficiency.

Preoperative intensity-modulated radiotherapy with a simultaneous integrated boost combined with Capecitabine in locally advanced rectal cancer: short-term results of a multicentric study

BACKGROUND

Preoperative radiotherapy (RT) in combination with fluoropyrimidine-based chemotherapy (CT) is the standard of care in patients with locally advanced, T3-T4 N0-2, rectal cancer (LARC). Given the correlation between RT dose-tumor response and the prognostic role of the tumor regression grade (TRG), treatment intensification represents an area of active investigation. The aim of the study was to analyze the role of RT dose-intensification in the preoperative treatment of LARC in terms of feasibility, efficacy and toxicity.

METHODS

We retrospectively analyzed patients with LARC treated with intensity-modulated radiotherapy (IMRT) and simultaneous integrated boost (SIB) at five Italian radiation oncology centers. Concurrent Capecitabine was administered. Treatment response was evaluated in terms of disease down-staging and TRG. Acute toxicity was evaluated according to the CTC-AE 4.0 scale.

RESULTS

A total of 76 patients were identified for this analysis. A dose of 45 Gy was prescribed to the entire mesorectum and pelvic lymph nodes with a median SIB dose of 54 Gy (range 52.5-57.5) to the tumor and corresponding mesorectum. Overall, 74/76 (97.4%) patients completed the planned RT, whereas 64/76 (84.2%) patients completed the prescribed CT. Eight (10.5%) patients developed grade 3-4 acute toxicity. Overall, 72/76 patients underwent surgery. The tumor and nodal down-staging was documented in 51 (70.8%) and 43 (67%) patients, respectively. Twenty (27.8%) patients obtained a pathologic complete response. Surgical morbidity was reported in 13/72 patients (18.1%).

CONCLUSIONS

Although retrospective in design, this study indicates that IMRT-SIB with a dose range of 52.5-57.5 Gy (median 54 Gy) and concomitant Capecitabine appears feasible, well tolerated and effective in terms of disease down-staging and pathological complete response. Long-term toxicity and the impact on disease control and patient survival will be evaluated with a longer follow-up time.

TRIAL REGISTRATION

NA.