Comparison of IMRT and VMAT plans with different energy levels using Monte-Carlo algorithm for prostate cancer

VMAT partial arc technique decreases dose to organs at risk in whole pelvic radiotherapy for prostate cancer when compared to full arc VMAT and IMRT

Whole pelvic radiotherapy (WPRT) can sterilize microscopic lymph node metastases in treatment of prostate cancer. WPRT, compared to prostate only radiotherapy (PORT), is associated with increased acute gastrointestinal, and hematological toxicities. To further explore minimizing normal tissue toxicities associated with WPRT in definitive IMRT for prostate cancer, this planning study compared dosimetric differences between static 9-field-IMRT, full arc VMAT, and mixed partial-full arc VMAT techniques. In this retrospective study, 12 prostate cancer patients who met the criteria for WPRT were randomly selected for this study. The initial volume, PTV46, included the prostate, seminal vesicles, and pelvic nodes with margin and was prescribed to 4600 cGy. The cone-down volume, PTV78, included the prostate and proximal seminal vesicles with margin to a total dose of 7800 cGy. For each CT image set, 3 plans were generated for each of the PTVs: an IMRT plan, a full arc (FA) VMAT plan, and a mixed partial-full arc (PFA) VMAT plan, using 6MV photons energy. According to RTOG protocols none of the plans had a major Conformity Index (CI) violation by any of the 3 planning techniques. PFA plan had the best mean CI index of 1.00 and significantly better than IMRT (p = 0.03) and FA (p = 0.007). For equivalent PTV coverage, the average composite gradient index of the PFA plans was better than the IMRT and the FA plans with values 1.92, 2.03, and 2.01 respectively. The defference was statistically significant between PFA/IMRT and PFA/FA, with p- values of < 0.001. The IMRT plans and the PFA plans provided very similar doses to the rectum, bladder, sigmoid colon, and femoral heads, which were lower than the dose in the FA plans. There was a significant decrease in the mean dose to the rectum from 4524 cGy with the FA to 4182 cGy with the PFA and 4091 cGy with IMRT (p < 0.001). The percent of rectum receiving 4000 cGy was also the highest with FA at 66.1% compared to 49.9% (PFA) and 47.5% (IMRT). There was a significant decrease in the mean dose to the bladder from 3922 cGy (FA) to 3551 cGy (PFA) and 3612 cGy (IMRT) (p < 0.001). The percent of bladder receiving 4000 cGy was also the highest with FA at 45.4% compared to 36.6% (PFA) and 37.4% (IMRT). The average mean dose to the sigmoid colon decreased from 4177 cGy (FA) to 3893 cGy (PFA) and 3819 cGy (IMRT). The average mean dose to the femoral heads decreased from 2091 cGy (FA) to 2026 cGy (PFA) and 1987 cGy (IMRT). Considering the improvement in plan quality indices recorded in this study including the dose gradient and the dose to organs at risk, mixed partial-full arc plans may be the preferred VMAT treatment technique over full arc plans for prostate cancer treatments that include nodal volumes.

Knowledge-Based Volumetric Modulated Arc Therapy Treatment Planning for Breast Cancer

Purpose:

To create and to validate knowledge-based volumetric modulated arc therapy (VMAT) models for breast cancer treatments without lymph node irradiation.

Materials and Methods:

One hundred VMAT-based breast plans (manual plans [MP]) were selected to create two knowledge-based VMAT models (breast left and breast right) using RapidPlan™. The plans were generated on Eclipse v15.5 (Varian Medical Systems, Palo Alto, CA) with 6 MV of a Novalis Tx equipped with a high-resolution multileaf collimator. The models were verified based on goodness-of-fit statistics using the coefficients of determination (R²) and Chi-square (χ²), and the goodness-of-estimation statistics through the mean square error (MSE). Geometrical and dosimetrical constraints were identified and removed from the RP models using statistical evaluation metrics and plots. For validation, 20 plans that integrate the models and 20 plans that do not were reoptimized with RP (closed and opened validation). Dosimetrical parameters of interest were used to compare MP versus RP plans for the Heart, Homolateral_Lung, Contralateral_Lung, and Contralateral_Breast. Optimization planning time and user independency were also analyzed.

Results:

The most unfavorable results of R² in both models for the organs at risk were as follows: for Contralateral_Lung 0.51 in RP right breast (RP_RB) and for Heart 0.60 in RP left breast (RP_LB). The most unfavorable results of χ² test were: for Contralateral_Breast 1.02 in RP_RB and for Heart 1.03 in RP_LB. These goodness-of-fit results show that no overfitting occurred in either of the models. There were no unfavorable results of mean square error (MSE, all < 0.05) in any of the two models. These goodness-of-estimation results show that the models have good estimation power. For closed validation, significant differences were found in RP_RB for Homolateral_Lung (all P ≤ 0.001), and in the RP_LB differences were found for the heart (all P ≤ 0.04) and for Homolateral_Lung (all P ≤ 0.022). For open validation, no statistically significant differences were obtained in either of the models. RP models had little impact on reducing optimization planning times for expert planners; nevertheless, the result showed a 30% reduction time for beginner planners. The use of RP models generates high-quality plans, without differences from the planner experience.

Conclusion:

Two RP models for breast cancer treatment using VMAT were successfully implemented. The use of RP models for breast cancer reduces the optimization planning time and improves the efficiency of the treatment planning process while ensuring high-quality plans.

Optimal tumor coverage with different beam energies by IMRT, VMAT and TOMO: Effects on patients with proximal gastric cancer

To compare the effects of different photon energies on radiation planning by intensity-modulated radiotherapy (IMRT), volumetric-modulated arc therapy (VMAT) and helical tomotherapy (TOMO) for proximal gastric cancer (PGC). Network analysis with microarray procession and gene ontology were used to identify the effect of radiotherapy (RT) on PGC. Then, we retrospectively analyzed 8 PGC patients after receiving irradiation with a prescribed dose of 50.4 Gy. The Pinnacle treatment planning system (TPS, V9.8) was used to generate IMRT and VMAT plans by using 6 or 10 MV. TOMO plans were calculated on the Tomotherapy Planning Station Hi-Art Version 4.2.3 workstation (Tomotherapy Incorporated, Madison, WI, USA). PGC is associated with high DNA repair ability. TOMO plan results in higher tumor coverage and a better conformity index than IMRT and VMAT. 10-MV VMAT yields better dosimetric quality of the gradient index than 6-MV VMAT (P = .012). TOMO was associated with a lower irradiation dose in the mean dose to the right kidney (P = .049), left kidney and heart than 6-MV IMRT and 6-MV VMAT. 6-MV IMRT plan presented a higher dose of lung Dmean (P = .017) than 10-MV IMRT. Additionally, VMAT, using a planning energy of 6 MV, was associated with a significantly higher left kidney Dmean (P = .018) and V10 (P = .036) than a planning energy of 10 MV. TOMO is a better RT plan not only for tumor coverage but also for sparing organs at risk. IMRT and VMAT plans with 10 MV beams are more suitable than 6 MV beams for PGC treatment.

Incidental testicular doses during volumetric-modulated arc radiotherapy in prostate cancer patients

PURPOSE

To compare the incidental testicular doses during volumetric-modulated arc therapy (VMAT) in patients receiving prostate-only and pelvic lymphatic irradiation.

MATERIALS AND METHODS

Testicular doses in 40 intermediate- and high-risk prostate cancer patients were determined on treatment planning system (TPS) using the VMAT technique at 6 MV. Scattered testicular doses were also measured by MOSFET detectors placed on testis surface. The testicular doses of patients treated with prostate-only and pelvic field irradiation were compared.

RESULTS

The median testicular doses measured per 200 cGy fraction by TPS and MOSFET detectors were 1.7 cGy (0.7-4.1 cGy) and 4.8 cGy (3.6-8.8 cGy), respectively. The TPS doses and MOSFET readings showed a significant strong correlation (Pearson r = 0.848, p < 0.001). The testicular doses measured by TPS (1.34 ± 0.36 cGy vs. 2.60 ± 0.95 cGy; p < 0.001) and MOSFET (4.52 ± 0.64 cGy vs. 6.56 ± 1.23 cGy; p < 0.001) were significantly lower in patients with prostate-only irradiation than in those with pelvic field irradiation. The mean cumulative scattered dose for prostate-only field delivering 78 Gy was 1.8 Gy and that for pelvic field irradiation was 2.6 Gy, consistent with the reported findings.

CONCLUSIONS

The patients with prostate-only irradiation received lower testicular doses than those with additional pelvic field irradiation possibly due to the increased scattered doses in large field irradiation using the VMAT technique. The clinical response to increased incidental testicular doses due to pelvic field irradiation remains unknown, and it warrants further investigation.

[Which photon energy for intensity-modulated radiotherapy and volumetric-modulated arctherapy in 2019?]

For more than a decade, the majority of radiation oncology centres have been delivering intensity-modulated radiotherapy (then volumetric-modulated arctherapy) with 6 MV photons as their standard of care. This « dogma » had been supported by the usual absence of dosimetric advantages with high-energy photons (15 to 18 MV or more), at least for the planning target volume and the dose received by the adjacent organs at risk, and by the neutron component as soon as the photon energy exceeds 10 MV. Recent data could question such a dogma. First, in 2019, one cannot avoid taking into account the integral dose, delivered outside the treated volume. Actually, most available data show that integral dose is higher with low energy photons (as 6 MV) than with higher energies. Moreover, recent studies have shown that the neutron component at high energies may have been overestimated in the past; in fact, the neutron dose appears to be lower, and sometimes much lower, than the dose we accept for imaging. Finally, a few cohort studies did not show any increase in second cancers incidence after high-energy photon radiotherapy. In such a context, the American Association of Physicists in Medicine (AAPM) TG 158 document, released a few months ago, clearly states that there is a trade-off between high- and low-energy treatments. High-energy therapy is associated with neutron production, while low-energy therapy results in higher stray photon dose. According to the AAPM, « the optimal energy is likely an intermediate such as 10 MV ».

Dosimetric comparison of vaginal vault brachytherapy vs applicator-guided stereotactic body radiotherapy with volumetric modulated arc therapy and helical tomotherapy for endometrium cancer patients

We performed this dosimetric study to compare a nonstandard volumetric modulated arc therapy (VMAT) and helical tomotherapy (HT) techniques with high-dose rate (HDR) brachytherapy (BRT) plan of vaginal vault in patients with postoperative endometrial cancer (EC). Twelve postoperative patients with early stage EC were included in this study. Three plans were performed for each patient; dosimetric and radiobiological comparisons were made using dose-volume histograms and equivalent dose for determining the planning target volume (PTV) coverages in brachytherapy and external beam radiotherapy, and organs-at-risk (OARs) doses between three different delivery techniques. All the plans achieved adequate dose coverage for PTV; however, the VMAT plan yielded better dose conformity, and the HT plan showed better homogeneity for target volume. With respect to the OARs, the bladder D_2cc was significantly lower in the BRT plan than in the VMAT and HT plans, with the highest bladder D_2cc value being observed in the HT plan. However, no difference was observed in the rectum D_2cc of the three plans. Other major advantages of the BRT plan over the VMAT and HT plans were the relatively lower body integral doses and femoral head doses as well as the fact that the integral doses were significantly lower in the BRT plan than in the VMAT and HT plans. This is the first dosimetric comparison of vaginal vault treatment for EC with BRT, VMAT, and HT plans. Our analyses showed the feasibility of stereotactic body radiotherapy technique as an alternative to HDR-BRT for postoperative management of EC patients.

Analysis of a volumetric-modulated arc therapy (VMAT) single phase prostate template as a class solution

Aim

To assess a class solution template for volumetric-modulated arc therapy (VMAT) for prostate cancer using plan analysis software.

Background

VMAT is a development of intensity-modulated radiotherapy (IMRT) with potential advantages for the delivery of radiotherapy (RT) in prostate cancer. Class solutions are increasingly used for facilitating RT planning. Plan analysis software provides an objective tool for evaluating class solutions.

Materials and methods

The class solution for VMAT was based on the current static field IMRT template. The plans of 77 prostate cancer patients were evaluated using a set of in-house plan quality metrics (scores) (PlanIQ™, Sun Nuclear Corporation). The metrics compared the class solution for VMAT planning with the IMRT template and the delivered clinical plan (CP). Eight metrics were associated with target coverage and ten with organs-at-risk (OAR). Individual metrics were summed and the combined scores were subjected to non-parametric analysis. The low-dose wash for both static IMRT and VMAT plans were evaluated using 40 Gy and 25 Gy isodose volumes.

Results

VMAT plans were of equal or better quality than the IMRT template and CP for target coverage (combined score) and OAR combined score. The 40 Gy isodose volume was marginally higher with VMAT than IMRT (4.9%) but lower than CP (-6.6%)(P = 0.0074). The 25 Gy volume was significantly lower with VMAT than both IMRT (-32.7%) and CP (-34.4%)(P < 0.00001).

Conclusions

Automated VMAT planning for prostate cancer is feasible and the plans are equal to or better than the current IMRT class solution and the delivered clinical plan.

Energy-dependent OAR sparing and dose conformity for total marrow irradiation of obese patients

Purpose

To investigate the effect on target coverage and organs at risk sparing by using 10 versus 6 MV for VMAT total marrow irradiation of obese patients.

Methods and Materials

Twenty‐six total marrow irradiation, TMI, treatment plans delivered between December 2014 and June 2017 were reviewed and 10 were chosen for replanning based on patient characteristics and plan metrics. Beam geometry and isocenter placement were conserved, energy was changed from 6 to 10 MV and plans were reoptimized. Resulting dose distributions were compared to original plans to evaluate any potential advantage of choosing one energy over the other.

Results

Target coverage and total monitor units were consistent between the 6 and 10 MV plans when averaged over all ten patients. Improvement in the conformity index (−11.0%, P = 0.009) when using 10 MV was statistically significant compared to the 6 MV plans. Volumes of normal tissue receiving 50%, 75%, and 90% Rx all decreased for the 10 MV plans compared to the original 6 MV plans. The mean dose to individual OARs decreased significantly for all investigated structures except for the lenses, oral cavity, and genitalia. The largest decreases in D_mean were found for the rectum (22.4%, P = 0.004) and bladder (18.1%, P = 0.005). The three highest priorities for sparing during plan optimization (lungs, liver, and heart), showed decreases of 7.6%, 16.1%, and 13.0%.

Conclusions

Use of a higher energy 10 MV beam provided similar dose to target while achieving increased OAR and normal tissue sparing for the patients reviewed in this study.

Dosimetric comparison of 3-dimensional conformal radiotherapy, volumetric modulated arc therapy, and helical tomotherapy for postoperative gastric cancer patients

PURPOSE

To compare dosimetric data for the planning target volume (PTV) and organs at risk (OARs) between 3-dimensional conformal radiotherapy (3DCRT), volumetric modulated arc therapy (VMAT), and helical tomotherapy [1].

MATERIALS AND METHODS

The dosimetric data for 15 gastric cancer patients treated with 3DCRT, VMAT, or HT techniques were used. Cumulative dosimetric parameters, homogeneity index (HI), and conformal index (CI) were compared for the PTV and OARs.

RESULTS

The average maximum doses of PTV were significantly higher in VMAT plans than in 3DCRT (p = 0.04) and HT (p = 0.02) plans, whereas minimum dose values were significantly lower in 3DCRT plans compared with VMAT (p < 0.001) and HT (p = 0.02) plans. Liver mean dose (D _mean) and D _mean values for both kidneys were significantly lower in HT plans than in 3DCRT and VMAT plans. The doses in high dose regions (V30-V45) using 3DCRT plans were significantly higher compared to both VMAT and HT plans. The bowel V5-V30 and V45 was significantly less in HT plans compared to VMAT plans. There were no significant differences in dose sparing of the spinal cord.

CONCLUSIONS

The HT plans reduced the maximum dose applied to the target and improved the conformality and homogeneity of radiation, while providing sufficient PTV coverage.

The impact of androgen deprivation therapy on setup errors during external beam radiation therapy for prostate cancer

PURPOSE

To determine whether setup errors during external beam radiation therapy (RT) for prostate cancer are influenced by the combination of androgen deprivation treatment (ADT) and RT.

MATERIALS AND METHODS

Data from 175 patients treated for prostate cancer were retrospectively analyzed. Treatment was as follows: concurrent ADT plus RT, 33 patients (19%); neoadjuvant and concurrent ADT plus RT, 91 patients (52%); RT only, 51 patients (29%). Required couch shifts without rotations were recorded for each megavoltage (MV) cone beam computed tomography (CBCT) scan, and corresponding alignment shifts were recorded as left-right (x), superior-inferior (y), and anterior-posterior (z). The nonparametric Mann-Whitney test was used to compare shifts by group. Pearson's correlation coefficient was used to measure the correlation of couch shifts between groups. Mean prostate shifts and standard deviations (SD) were calculated and pooled to obtain mean or group systematic error (M), SD of systematic error (Σ), and SD of random error (σ).

RESULTS

No significant differences were observed in prostate shifts in any direction between the groups. Shifts on CBCT were all less than setup margins. A significant positive correlation was observed between prostate volume and the z‑direction prostate shift (r = 0.19, p = 0.04), regardless of ADT group, but not between volume and x‑ or y‑direction shifts (r = 0.04, p = 0.7; r = 0.03, p = 0.7). Random and systematic errors for all patient cohorts and ADT groups were similar.

CONCLUSION

Hormone therapy given concurrently with RT was not found to significantly impact setup errors. Prostate volume was significantly correlated with shifts in the anterior-posterior direction only.

A Dosimetric Comparison between Conventional Fractionated and Hypofractionated Image-guided Radiation Therapies for Localized Prostate Cancer

Background:

Image-guided radiation therapy (IGRT) is the preferred method for curative treatment of localized prostate cancer, which could improve disease outcome and reduce normal tissue toxicity reaction. IGRT using cone-beam computed tomography (CBCT) in combination with volumetric-modulated arc therapy (VMAT) potentially allows smaller treatment margins and dose escalation to the prostate. The aim of this study was to compare the difference of dosimetric diffusion in conventional IGRT using 7-field, step-and-shoot intensity-modulated radiation therapy (IMRT) and hypofractionated IGRT using VMAT for patients with localized prostate cancer.

Methods:

We studied 24 patients who received 78 Gy in 39 daily fractions or 70 Gy in 28 daily fractions to their prostate with/without the seminal vesicles using IMRT (n = 12) or VMAT (n = 12) for prostate cancer between November 2013 and October 2015. Image guidance was performed using kilovoltage CBCT scans equipped on the linear accelerator. Offline planning was performed using the daily treatment images registered with simulation computed tomography (CT) images. A total of 212 IMRT plans in conventional cohort and 292 VMAT plans in hypofractionated cohort were enrolled in the study. Dose distributions were recalculated on CBCT images registered with the planning CT scanner.

Results:

Compared with 7-field, step-and-shoot IMRT, VMAT plans resulted in improved planning target volume (PTV) D95% (7663.17 ± 69.57 cGy vs. 7789.17 ± 131.76 cGy, P < 0.001). VMAT reduced the rectal D25 (P < 0.001), D35 (P < 0.001), and D50 (P < 0.001), bladder V50 (P < 0.001), D25 (P = 0.002), D35 (P = 0.028), and D50 (P = 0.029). However, VMAT did not statistically significantly reduce the rectal V50, compared with 7-field, step-and-shoot IMRT (25.02 ± 5.54% vs. 27.43 ± 8.79%, P = 0.087).

Conclusions:

To deliver the hypofractionated radiotherapy in prostate cancer, VMAT significantly increased PTV D95% dose and decreased the dose of radiation delivered to adjacent normal tissues comparing to 7-field, step-and-shoot IMRT. Daily online image-guidance and better management of bladder and rectum could make a more precise treatment delivery.

Dosimetric comparison of intensity-modulated radiotherapy and volumetric-modulated arc radiotherapy in patients with prostate cancer: a meta-analysis

Intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) are two main radiotherapy techniques. The aim of this study is to explore which is the preferred technique in prostate treatment through the related publica-tions and meta-analysis. Two authors independently identified all relevant articles available regarding eligibility criteria on PubMed, Embase, and Cochrane Library databases until December 2015. Publication bias was evaluated with funnel plot, and statistical analyses were performed with Stata software. P < 0.05 was thought statistically significant. Ten studies comprised a total of 110 patients; in total 110 IMRT plans and 110 VMAT plans that were included in this study. V40, V60, and V70 of rectum were significantly decreased in VMAT than in IMRT. However, V50 of rectum and V40, V50, V60, V70 of bladder had no statistical differences between IMRI and VMAT plans. Compared with IMRT, the treatment time and MUs of VMAT were significantly lower. VMAT protects rectum better than IMRT and improves the delivery efficiency. VMAT may be the preferred modality for treating prostate cancer.

Is it essential to use fiducial markers during cone-beam CT-based radiotherapy for prostate cancer patients?

PURPOSE

To compare soft-tissue cone-beam computed tomography (CBCT-P) and fiducial marker (CBCT-FM)-based image guided radiotherapy in prostate cancer patients.

MATERIALS AND METHODS

Sixteen prostate cancer patients were treated with volumetric modulated arc therapy. Manual alignment using CBCT-P and CBCT-FM was performed for each patient. Couch shifts were calculated and compared between methods in the left-right (x), superior-inferior (y), and anterior-posterior (z) directions.

RESULTS

CBCT-P and CBCT-FM alignments were compared using 252 scans from the 16 patients. Mean displacement from zero was 2.4 ± 1.3, 1.7 ± 1.2, and 1.8 ± 1.1 mm for CBCT-P and 2.3 ± 1.3, 1.7 ± 1.1 and 1.8 ± 1.1 mm for CBCT-FM in the x, y and z directions, respectively. There was no difference in median displacement between CBCT-P and CBCT-FM; however, there was a significant positive correlation between CBCT-P- and CBCT-FM-based displacements in the x (r = 0.881; p < 0.001), y (r = 0.789; p < 0.001) and z (r = 0.856; p < 0.001) directions by linear regression analysis. Systematic deviations within each group were <1 mm; however, random and systematic errors were similar in the x and y directions but larger in the z direction.

CONCLUSION

Our study demonstrated that CBCT-FM was not superior to CBCT-P for image-guided radiotherapy in prostate cancer patients.

The dosimetric impact of different photon beam energy on RapidArc radiotherapy planning for cervix carcinoma

The main purpose of this study is to know the effect of three different photon energies viz., 6, 10, and 15 mega voltage (MV) on RapidArc (RA) planning for deep-seated cervix tumor and to develop clinically acceptable RA plans with suitable photon energy. RA plans were generated for 6, 10, and 15 MV photon energies for twenty patients reported with cervix carcinoma. RA plans were evaluated in terms of planning target volume (PTV) coverage, dose to organs at risk (OARs), conformity index (CI), homogeneity index (HI), gradient measure, external volume index of dose distribution produced, total number of monitor units (MUs), nontumor integral dose (ID), and low dose volume of normal tissue. A two-sample paired t-test was performed to compare the dosimetric parameters of RA plans. Irrespective of photon energy used for RA planning, plans were dosimetrically similar in terms of PTV coverage, OARs sparing, CI and HI. The numbers of MUs were 13.4 ± 1.4% and 18.2 ± 1.5% higher and IDs were 2.7 ± 0.8% and 3.7 ± 0.9% higher in 6 MV plans in comparison to that in the 10 and 15 MV plans, respectively. V1Gy, V2Gy, V3Gy, and V4Gy were higher in 6 MV plans in comparison to that in 10 and 15 MV plans. Based on this study, 6 MV photon beam is a good choice for RA planning in case of cervix carcinoma, as it does not deliver additional exposure to patients caused by photoneutrons produced in high energy beams.

Dose-volume histogram comparison between static 5-field IMRT with 18-MV X-rays and helical tomotherapy with 6-MV X-rays

We treated prostate cancer patients with static 5-field intensity-modulated radiation therapy (IMRT) using linac 18-MV X-rays or tomotherapy with 6-MV X-rays. As X-ray energies differ, we hypothesized that 18-MV photon IMRT may be better for large patients and tomotherapy may be more suitable for small patients. Thus, we compared dose-volume parameters for the planning target volume (PTV) and organs at risk (OARs) in 59 patients with T1-3 N0M0 prostate cancer who had been treated using 5-field IMRT. For these same patients, tomotherapy plans were also prepared for comparison. In addition, plans of 18 patients who were actually treated with tomotherapy were analyzed. The evaluated parameters were homogeneity indicies and a conformity index for the PTVs, and D2 (dose received by 2% of the PTV in Gy), D98, Dmean and V10-70 Gy (%) for OARs. To evaluate differences by body size, patients with a known body mass index were grouped by that index ( <21; 21-25; and >25 kg/m(2)). For the PTV, all parameters were higher in the tomotherapy plans compared with the 5-field IMRT plans. For the rectum, V10 Gy and V60 Gy were higher, whereas V20 Gy and V30 Gy were lower in the tomotherapy plans. For the bladder, all parameters were higher in the tomotherapy plans. However, both plans were considered clinically acceptable. Similar trends were observed in 18 patients treated with tomotherapy. Obvious trends were not observed for body size. Tomotherapy provides equivalent dose distributions for PTVs and OARs compared with 18-MV 5-field IMRT. Tomotherapy could be used as a substitute for high-energy photon IMRT for prostate cancer regardless of body size.

Intensity-modulated radiotherapy and volumetric-modulated arc therapy have distinct clinical advantages in non-small cell lung cancer treatment

This study was conducted to compare the efficacy of intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) in delivering the planned dosage in the treatment of non-small cell lung cancer (NSCLC). Between September 2013 and March 2014, 125 NSCLC patients were randomly chosen and allocated to the IMRT group (n = 65) and VMAT group (n = 60). We compared multiple parameters such as target dose, organ dosimetry, monitor unit (MU) and time of therapy between IMRT and VMAT groups. The prescribed dose coverage of both planning techniques was 95 % of the planning target volumes (PTVs). PTV 95 % and homogeneous index in IMRT plan were greater than those in VMAT plan (both P < 0.05), while no significant difference in conformity index was observed (P > 0.05). The mean total lung V5 and V10 in VMAT group were markedly higher than those in IMRT group, but the V20, V30, and V40 in VMAT group were significantly lower (all P < 0.05), but no statistically significant difference was observed in V15 and V20 (P > 0.05). Furthermore, the planning spine and esophagus at risk volume showed no statistical significances in both groups (P > 0.05). MU of IMRT plan was about 4.2 % less than that of VMAT plan, which was statistically significant (P < 0.001). Both IMRT and VMAT had significant advantages in the treatment of NSCLC. The IMRT may be better for NSCLC patients with poor pulmonary function, and VMAT may be recommended for NSCLC patients with normal pulmonary function.