A fast radiotherapy paradigm for anal cancer with volumetric modulated arc therapy (VMAT)

Deep-neural network approaches for predicting 3D dose distribution in intensity-modulated radiotherapy of the brain tumors

PURPOSE

The aim of this study is to reduce treatment planning time by predicting the intensity-modulated radiotherapy 3D dose distribution using deep learning for brain cancer patients. "For this purpose, two different approaches in dose prediction, i.e., first only planning target volume (PTV) and second PTV with organs at risk (OARs) as input of the U-net model, are employed and their results are compared."

METHODS AND MATERIALS

The data of 99 patients with glioma tumors referred for IMRT treatment were used so that the images of 90 patients were regarded as training datasets and the others were for the test. All patients were manually planned and treated with sixth-field IMRT; the photon energy was 6MV. The treatment plans were done with the Collapsed Cone Convolution algorithm to deliver 60 Gy in 30 fractions.

RESULTS

The obtained accuracy and similarity for the proposed methods in dose prediction when compared to the clinical dose distributions on test patients according to MSE, dice metric and SSIM for the Only-PTV and PTV-OARs methods are on average (0.05, 0.851, 0.83) and (0.056, 0.842, 0.82) respectively. Also, dose prediction is done in an extremely short time.

CONCLUSION

The same results of the two proposed methods prove that the presence of OARs in addition to PTV does not provide new knowledge to the network and only by defining the PTV and its location in the imaging slices, does the dose distribution become predictable. Therefore, the Only-PTV method by eliminating the process of introducing OARs can reduce the overall designing time of treatment by IMRT in patients with glioma tumors.

Dosimetric comparison between intensity-modulated radiation therapy and volumetric-modulated arc therapy to enhance bladder and bowel

Prostate cancer is the second most common cancer in men. Two common radiotherapy techniques, intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc radiotherapy (VMAT), are used for treatment. This study aimed to compare the two techniques for sparing the bladder and bowel. Computed tomography data from prostate cancer patients were analyzed to define the clinical target volume (CTV) and planning target volume (PTV). Treatment plans were generated with Monte Carlo algorithms, and dosimetric analysis was performed using the Monaco Treatment Planning System (TPS). We compared IMRT and VMAT for prostate cancer PTV coverage (% Ref. Volume), with VMAT showing slightly better coverage (98.885±1.704) compared to IMRT (98.594±0.923). VMAT also demonstrated improved PTV conformity. Additionally, VMAT was superior in sparing the bladder (% V4500<40%), while IMRT performed better in bowel preservation (mean Ref. volume CC<195).

Half-beam volumetric-modulated arc therapy in adjuvant radiotherapy for gynecological cancers

PURPOSE

The purpose of this study is to introduce half-beam volumetric-modulated arc therapy (HVMAT), an innovative treatment planning technique from our work, for reducing dose to the organs at risk (OAR) during adjuvant radiotherapy for gynecological cancers.

METHODS AND MATERIALS

Seventy-two treatment plans of 36 patients with gynecological cancers receiving adjuvant radiotherapy were assessed. Among them, 36 plans were designed using HVMAT and paired with the other 36 traditional volumetric-modulated arc therapy (VMAT) plans for each patient. The main uniqueness of the HVMAT designs was that it consisted of two opposite-shielded half-beam fields rotated inversely in two coplanar arcs, collocating with the specially-devised avoidance structures to enhance the control of the OAR doses. The dose distributions in HVMAT and VMAT were evaluated and compared using the random effects model.

RESULTS

The ratios of OAR doses in HVMAT compared with VMAT showed a comprehensive OAR dose reduction when using HVMAT (V_20Gy : bladder, 0.92; rectum, 0.95; V_30Gy : bowel, 0.91; femoral heads, 0.66), except for the ilium (V_30Gy : 1.12). The overall mean difference for each OAR across V_40Gy , V_30Gy , V_20Gy , and bowel V_15Gy was statistically significant (almost all p < 0.001). In addition, HVMAT promoted a better conformity index, homogeneity index, D_2% , and V_107% of the planning target volume (all p < 0.001).

CONCLUSIONS

HVMAT is capable of generating deep double-concave dose distributions with the advantage of reducing dose to several OARs simultaneously. It is highly recommended for pelvic irradiation, especially for treating gynecological cancers in adjuvant radiotherapy.

Dosimetric comparison of volumetric modulated arc therapy and intensity modulated radiation therapy for anal cancer

Aim:

Volumetric modulated arc therapy (VMAT), an extension of intensity modulated radiation therapy (IMRT), employs modifications in gantry rotation speed, machine dose rate and multi-leaf collimator motion to deliver a three-dimensional dose distribution. This study compared VMAT to IMRT for patients with anal carcinoma.

Materials and Methods:

Sixteen patients previously treated with IMRT were retrospectively selected. Each patient received a total dose of 57·6–63·0 Gy in 1·8 Gy fractions. A single- or double-isocenter multi-arc VMAT treatment plan was generated using Eclipse RapidArc system with the same computed tomography image sets and optimisation constraints used for IMRT. Dose–volume histograms (DVHs) for planning target volumes (PTVs) and organs at risk (OARs), and monitor units (MUs) and beam on times (BOTs) were used for comparison.

Results:

IMRT and VMAT plans showed insignificant differences in PTV homogeneity and conformity and sparing hips and bowel. VMAT required fewer mean MU and shorter BOT per plan (1,597 MU, 2·66 min) compared to IMRT (2,571 MU, 4·29 min) with p < 0·0001.

Conclusions:

Fewer MU and shorter BOT for VMAT may decrease the damage from secondary radiation and treatment delivery uncertainty due to intra-fraction tumour motion, leading to higher machine throughput and improving patient comfort, with less treatment time.

Proton beam radiotherapy for anal and rectal cancers

Gastrointestinal cancers are bordered by radiosensitive visceral organs, resulting in a narrow therapeutic window. The search for more efficacious and tolerable therapies raises the possibility that proton beam therapy's (PBT) physical and dosimetric differences from conventional therapy may be better suited to treat both primary and recurrent disease, which carries its own unique challenges. Currently, the maximal efficacy of radiation plans for primary and recurrent anorectal cancer is constrained by delivery techniques and modalities which must consider feasibility challenges and toxicity secondary to exposure of organs at risk (OARs). Studies using volumetric modulated arc therapy (VMAT) and intensity modulated radiation therapy (IMRT) demonstrate that more precise dose delivery to target volumes improves local control rates and reduces complications. By reducing the low-to-moderate radiation dose-bath to bone marrow, small and large bowel, and skin, PBT may offer an improved side-effect profile. The potential to reduce toxicity, increase patient compliance, minimize treatment breaks, and enable dose escalation or hypofractionation is appealing. In cases where prognosis is favorable, PBT may mitigate long-term morbidity such as secondary malignancies, femoral fractures, and small bowel obstruction.

The role of volumetric modulated arc therapy (VMAT) in gynaecological radiation therapy: A dosimetric comparison of intensity modulated radiation therapy versus VMAT

INTRODUCTION

For gynaecological cancers, volumetric modulated arc therapy (VMAT) offers comparable plan quality with shorter treatment delivery times when compared to intensity modulated radiation therapy (IMRT).

METHODS

The clinical IMRT plans of twenty gynaecological cancer patients were compared with a retrospectively generated VMAT plan. Planning target volume (PTV) metrics compared were D95 > 99%, homogeneity index, and conformity index. Organs at risk (OAR) doses compared were bladder V45 < 35%, bowel V40 < 30%, femoral head and neck (FHN) V30 < 50%, V44 < 35% and V44 < 5%. Plan quality was also assessed by comparing the monitor units (MU), treatment time and the patient-specific quality assurance results.

RESULTS

VMAT and IMRT resulted in comparable PTV coverage with D95 values of 98.92% ± 0.69% and 98.91% ± 1.43% respectively, and homogeneity index values of 0.08 ± 0.02 (VMAT) and 0.08 ± 0.03 (IMRT). The conformity index for VMAT was 0.93 ± 0.04 and IMRT 0.85 ± 0.06 (P < 0.001). For the bowel tolerance (40 Gy < 30%) VMAT resulted in 22.39% ± 12.5% compared to 28.8% ± 16.78% for IMRT, with bladder and FHN VMAT doses also lower. VMAT MU were 694.35 ± 126.56 compared to 606.8 ± 96.16 for IMRT (P < 0.01). Treatment times of 6.6 ± 0.82 min and 2.47 ± 0.35 min were achieved for IMRT and VMAT respectively.

CONCLUSION

VMAT showed improvements in sparing OAR compared to IMRT. Target volume coverage with VMAT was equivalent or better than that of IMRT. These results in conjunction with the confirmed shorter treatment delivery time, have led to the development and implementation of a clinical protocol.

Prospective evaluation of acute toxicity and patient reported outcomes in anal cancer and plan optimization

BACKGROUND AND PURPOSE

Chemoradiotherapy (CRT) is the standard therapy for localized anal cancer (AC), but this treatment is associated with substantial toxicity. However, there is a lack of prospectively collected toxicity and patient reported outcome (PRO) data from larger cohorts. The purpose was to prospectively collect and determine agreement between physician assessed toxicity (CTCAE) and PRO during and after CRT and to compare IMRT, VMAT and proton-based planning in a subgroup of patients.

MATERIAL AND METHODS

Patients, treated with CRT for AC, were included between 2015 and 2017. NCI-CTCAE v.4.0, EORTC QLQ-C30 and CR29 data were collected baseline, mid-therapy, end-of therapy and 2-4 weeks posttherapy. Treatment planning with 5- or 6-fixed field IMRT, 2 and 3 arc VMAT, and 3- and 4-field proton plans were compared.

RESULTS

One-hundred patients were included. Both CTCAE and PROs related to acute toxicity reached a maximum at end of therapy. Incidences of PROs were markedly higher with only slight to fair agreement to CTCAE, (κ 13-37). Comparative planning revealed dosimetric equality of IMRT and VMAT plans, but superiority of proton plans.

CONCLUSIONS

The high incidence of PRO scores and weak agreement to CTCAE suggest that PROs are important tools complementary to CTCAE in evaluating patient symptoms during and after CRT. Proton therapy has the potential to lower radiation doses to most organs at risk.

Concurrent chemoradiation with volumetric modulated Arc therapy of patients treated for anal cancer-acute toxicity and treatment outcome

BACKGROUND

to report the acute toxicity and clinical results in patients with anal cancer treated with volumetric modulated arc therapy (VMAT) concomitant with chemotherapy.

METHODS

A cohort of 21 patients with histologically confirmed squamous cell carcinoma of the anal canal was treated with VMAT and chemotherapy. Dose prescription was 39.6 Gy, 1.8 Gy/ fraction for the elective nodal PTV, the macroscopic (tumor and involved lymph nodes) PTV doses were 14.4 Gy up to a total dose of 54 Gy in 4 patients and 19.8 up to 59.4 Gy in 15 patients. One patient received a boost dose of 18 Gy up to a total dose of 57.6 Gy and another one was treated with 36 Gy and boost of 19.8 Gy up to a total dose of 55.8 Gy. Chemotherapy with MMC and 5-FU/Capecitabine was administered concomitantly. End points were local control (LC), disease-free survival (DFS) and overall survival (OS).

RESULTS

Median follow-up time was 35.5 months. Two year OS was 91%, DFS was 73% and LRC was 81%. Acute dermatological toxicity G3 was recorded in one patient, ten patients (47.6%) experienced a G2 skin toxicity, while G1 toxicity was registered in eight patients (38%). One patient developed Grade 3 acute gastrointestinal (GI) toxicity, two patients (9.5%) experienced grade 2 acute GI toxicity and ten patients (47.6%) G1 toxicity. Acute genitourinary toxicity G1 was recorded in ten patients (47.6%).

CONCLUSIONS

Our results support VMAT as standard radiotherapy technique in the treatment of patients with anal cancer.

Comparative study on dosimetry of VMAT and IMRT in assisted radiotherapy after radical resection of rectal cancer

The present study compared the dosimetric differences of volumetric modulated arc therapy (VMAT) and 7-field intensity modulated radiation therapy technology (7F-IMRT) in assisted radiotherapy plan after resection of rectal carcinoma. Ten cases of patients at stages II–III of rectal cancer transabdominal resection with postoperative pelvic radiotherapy underwent 7F-IMRT and VMAT radiotherapy plan design using the CMS Monaco treatment planning system. We compared the dose distribution, the number of organs at risk and the number of machines in the two groups. The 7F-IMRT plans conformal index (CI) was 0.8319±0.0143 and VMAT plans CI was 0.838±0.164. Both plans reached up to the 95% isodose line at a volume of 100% planning target volume (PTV), the 7F- IMRT plans homogeneity index (HI) was 1.0760±0.0179, and the VMAT plans HI was 1.0821±0.0143. CI and HI had no statistical difference. With regard to S40, the V50 dose volume of the small intestine was endangered, and the VMAT plan was better than that of the 7F-IMRT plan, and the difference was statistically significant (P<0.05). The machine hop numbers of the two types of plans were 594.1±36.1 and 793.2 ±56.6 for for VMAT and 7F-IMRT, respectively. The VMAT plan was less than htat of the 7F-IMRT and the difference was statistically significant (P<0.05). Patients to whom VMAT techniques were utilized after resection of rectal cancer obtained an equal or a superior dose distribution compared with the IMRT plan. VMAT had important significance in protecting the small intestine, while significantly reducing treatment time.

Genital invasion or perigenital spread may pose a risk of marginal misses for Intensity Modulated Radiotherapy (IMRT) in anal cancer

BACKGROUND

While intensity modulated radiotherapy (IMRT) in anal cancer is feasible and improves high-dose conformality, the current RTOG/AGITG contouring atlas and planning guidelines lack specific instructions on how to proceed with external genitalia. Meanwhile, the RTOG-Protocol 0529 explicitly recommends genital sparing on the basis of specific genital dose constraints. Recent pattern-of-relapse studies based on conventional techniques suggest that marginal miss might be a potential consequence of genital sparing. Our goal is to outline the potential scope and increase the awareness for this clinical issue.

METHODS

We present and discuss four patients with perigenital spread in anal cancer in both early and advanced stages (three at time of first diagnosis and one in form of relapse). Genital/perigenital spread was observed once as direct genital infiltration and thrice in form of perigenital lymphatic spread.

RESULTS

We review the available data regarding the potential consequences of genital sparing in anal cancer. Pattern-of-relapse studies in anal cancer after conventional radiotherapy and the current use of IMRT in anal cancer are equivocal but suggest that genital sparing may occasionally result in marginal miss. An obvious hypothesis suggested by our report is that perigenital lymphovascular invasion might be associated with manifest inguinal N+ disease.

CONCLUSIONS

Local failure has low salvage rates in recent anal cancer treatment series. Perigenital spread may pose a risk of marginal misses in IMRT in anal cancer. To prevent marginal misses, meticulous pattern-of-relapse analyses of controlled IMRT-series are warranted. Until their publication, genital sparing should be applied with caution, PET/CT should be used when possible and meeting genital dose constraints should not be prioritized over CTV coverage, especially (but not only) in stage T3/4 and N+ disease.

Squamous-cell carcinoma of the anus: progress in radiotherapy treatment

Chemoradiotherapy is the standard-of-care treatment of squamous-cell carcinoma of the anus (SCCA), and this has not changed in decades. Radiation doses of 50-60 Gy, as used in many phase III trials, result in substantial late morbidities and fail to control larger and node-positive tumours. Technological advances in radiation therapy are improving patient outcomes and quality of life, and should be applied to patients with SCCA. Modern techniques such as intensity-modulated radiotherapy (IMRT), rotational IMRT, image-guided radiotherapy using cone-beam CT, and stereotactic techniques have enabled smaller margins and highly conformal plans, resulting in decreased radiation doses to the organs at risk and ensuring a shorter overall treatment time. In this Perspectives article, the use of novel approaches to target delineation, optimized radiotherapy techniques, adaptive radiotherapy, dose-escalation with external-beam radiotherapy (EBRT) or brachytherapy, and the potential for modified fractionation are discussed in the context of SCCA.

Image-guided volumetric modulated arc therapy for breast cancer: a feasibility study and plan comparison with three-dimensional conformal and intensity-modulated radiotherapy

OBJECTIVE

To test the feasibility of volumetric modulated arc therapy (VMAT) in breast cancer and to compare it with three-dimensional conformal radiotherapy (3D-CRT) as conventional tangential field radiotheraphy (conTFRT).

METHODS

12 patients (Stage I, 8: 6 left breast cancer and 2 right breast cancer; Stage II, 4: 2 on each side). Three plans were calculated for each case after breast-conserving surgery. Breast was treated with 50 Gy in four patients with supraclavicular lymph node inclusion, and in eight patients without the node inclusion. Multiple indices and dose parameters were measured.

RESULTS

V95% was not achieved by any modality. Heterogeneity index: 0.16 (VMAT), 0.13 [intensity-modulated radiotherapy (IMRT)] and 0.14 (conTFRT). Conformity index: 1.06 (VMAT), 1.15 (IMRT) and 1.69 (conTFRT). For both indices, IMRT was more effective than VMAT (p=0.009, p=0.002). Dmean and V20 for ipsilateral lung were lower for IMRT than VMAT (p=0.0001, p=0.003). Dmean, V2 and V5 of contralateral lung were lower for IMRT than VMAT (p>0.0001, p=0.005). Mean dose and V5 to the heart were lower for IMRT than for VMAT (p=0.015, p=0.002).

CONCLUSION

The hypothesis of equivalence of VMAT to IMRT was not confirmed for planning target volume parameter or dose distribution to organs at risk. VMAT was inferior to IMRT and 3D-CRT with regard to dose distribution to organs at risk, especially at the low dose level.

ADVANCES IN KNOWLEDGE

New technology VMAT is not superior to IMRT or conventional radiotherapy in breast cancer in any aspect.

Single-arc volumetric-modulated arc therapy (sVMAT) as adjuvant treatment for gastric cancer: dosimetric comparisons with three-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT)

To compare the dosimetric differences between the single-arc volumetric-modulated arc therapy (sVMAT), 3-dimensional conformal radiotherapy (3D-CRT), and intensity-modulated radiotherapy (IMRT) techniques in treatment planning for gastric cancer as adjuvant radiotherapy. Twelve patients were retrospectively analyzed. In each patient's case, the parameters were compared based on the dose-volume histogram (DVH) of the sVMAT, 3D-CRT, and IMRT plans, respectively. Three techniques showed similar target dose coverage. The maximum and mean doses of the target were significantly higher in the sVMAT plans than that in 3D-CRT plans and in the 3D-CRT/IMRT plans, respectively, but these differences were clinically acceptable. The IMRT and sVMAT plans successfully achieved better target dose conformity, reduced the V20/30, and mean dose of the left kidney, as well as the V20/30 of the liver, compared with the 3D-CRT plans. And the sVMAT technique reduced the V20 of the liver much significantly. Although the maximum dose of the spinal cord were much higher in the IMRT and sVMAT plans, respectively (mean 36.4 vs 39.5 and 40.6Gy), these data were still under the constraints. Not much difference was found in the analysis of the parameters of the right kidney, intestine, and heart. The IMRT and sVMAT plans achieved similar dose distribution to the target, but superior to the 3D-CRT plans, in adjuvant radiotherapy for gastric cancer. The sVMAT technique improved the dose sparings of the left kidney and liver, compared with the 3D-CRT technique, but showed few dosimetric advantages over the IMRT technique. Studies are warranted to evaluate the clinical benefits of the VMAT treatment for patients with gastric cancer after surgery in the future.

A comprehensive comparison of IMRT and VMAT plan quality for prostate cancer treatment

PURPOSE

We performed a comprehensive comparative study of the plan quality between volumetric-modulated arc therapy (VMAT) and intensity-modulated radiation therapy (IMRT) for the treatment of prostate cancer.

METHODS AND MATERIALS

Eleven patients with prostate cancer treated at our institution were randomly selected for this study. For each patient, a VMAT plan and a series of IMRT plans using an increasing number of beams (8, 12, 16, 20, and 24 beams) were examined. All plans were generated using our in-house-developed automatic inverse planning (AIP) algorithm. An existing eight-beam clinical IMRT plan, which was used to treat the patient, was used as the reference plan. For each patient, all AIP-generated plans were optimized to achieve the same level of planning target volume (PTV) coverage as the reference plan. Plan quality was evaluated by measuring mean dose to and dose-volume statistics of the organs at risk, especially the rectum, from each type of plan.

RESULTS

For the same PTV coverage, the AIP-generated VMAT plans had significantly better plan quality in terms of rectum sparing than the eight-beam clinical and AIP-generated IMRT plans (p < 0.0001). However, the differences between the IMRT and VMAT plans in all the dosimetric indices decreased as the number of beams used in IMRT increased. IMRT plan quality was similar or superior to that of VMAT when the number of beams in IMRT was increased to a certain number, which ranged from 12 to 24 for the set of patients studied. The superior VMAT plan quality resulted in approximately 30% more monitor units than the eight-beam IMRT plans, but the delivery time was still less than 3 min.

CONCLUSIONS

Considering the superior plan quality as well as the delivery efficiency of VMAT compared with that of IMRT, VMAT may be the preferred modality for treating prostate cancer.

Volumetric modulated arc therapy: a review of current literature and clinical use in practice

Volumetric modulated arc therapy (VMAT) is a novel radiation technique, which can achieve highly conformal dose distributions with improved target volume coverage and sparing of normal tissues compared with conventional radiotherapy techniques. VMAT also has the potential to offer additional advantages, such as reduced treatment delivery time compared with conventional static field intensity modulated radiotherapy (IMRT). The clinical worldwide use of VMAT is increasing significantly. Currently the majority of published data on VMAT are limited to planning and feasibility studies, although there is emerging clinical outcome data in several tumour sites. This article aims to discuss the current use of VMAT techniques in practice and review the available data from planning and clinical outcome studies in various tumour sites including prostate, pelvis (lower gastrointestinal, gynaecological), head and neck, thoracic, central nervous system, breast and other tumour sites.

Planning analysis for locally advanced lung cancer: dosimetric and efficiency comparisons between intensity-modulated radiotherapy (IMRT), single-arc/partial-arc volumetric modulated arc therapy (SA/PA-VMAT)

Purpose

To analyze the differences between the intensity-modulated radiotherapy (IMRT), single/partial-arc volumetric modulated arc therapy (SA/PA-VMAT) techniques in treatment planning for locally advanced lung cancer.

Materials and methods

12 patients were retrospectively studied. In each patient's case, several parameters were analyzed based on the dose-volume histograms (DVH) of the IMRT, SA/PA-VMAT plans respectively. Also, each plan was delivered to a phantom for time comparison.

Results

The SA-VMAT plans showed the superior target dose coverage, although the minimum/mean/maximum doses to the target were similar. For the total and contralateral lungs, the higher V_5/10, lower V_20/30 and mean lung dose (MLD) were observed in the SA/PA-VMAT plans (p < 0.05, respectively). The PA-VMAT technique improves the dose sparing (V₂₀, V₃₀ and MLD) of the controlateral lung more notably, comparing to those parameters of the IMRT and SA-VMAT plans respectively. The delivered monitor units (MUs) and treatment times were reduced significantly with VMAT plans, especially PA-VMAT plans (for MUs: mean 458.3 vs. 439.2 vs. 435.7 MUs, p < 0.05 and for treatment time: mean 13.7 vs. 10.6 vs. 6.4 minutes, p < 0.01).

Conclusions

The SA-VMAT technique achieves highly conformal dose distribution to the target. Comparing to the IMRT plans, the higher V_5/10, lower V_20/30 and MLD were observed in the total and contralateral lungs in the VMAT plans, especially in the PA-VMAT plans. The SA/PA-VMAT plans also reduced treatment time with more efficient dose delivering. But the clinical benefit of the VMAT technique for locally advanced lung cancer needs further investigations.

Curcumin decreases survival of Hep3B liver and MCF-7 breast cancer cells: the role of HIF

BACKGROUND

Curcumin, a commonly used spice, affects the activities of cytokines, enzymes, and transcription factors that are linked to inflammation. Furthermore, curcumin has been assigned tumor growth inhibiting effects, possibly mediated by promoting hypoxia-inducible factor (HIF) degradation. HIFs are transcription factors that play a central role in the adaptation and response to low oxygen levels in metazoan cells. However, curcumin also exhibits properties of an iron chelator indicating its potential of inhibiting HIF-α prolyl hydroxylase (PHD) activity.

METHODS

We were interested in clarifying these divergent actions of curcumin in due consideration of the effects on radio-therapy. Thus, concentration- and time-dependent effects of curcumin on HIF-α and -β protein levels and activity in hepatoma and breast carcinoma cell cultures under normoxic and hypoxic conditions were studied.

RESULTS

It was shown that HIF-1α accumulated in normoxia after the application of higher doses of the drug. Curcumin proved to lower HIF-1α and HIF-2α protein levels in hypoxia. HIF-1β (ARNT; arylhydrocarbon nuclear translocator) protein levels and HIF transcriptional activity were reduced in normoxia and hypoxia after 4 h and 24 h incubation periods. Furthermore, curcumin treatment negatively impacted on clonogenic cell survival of Hep3B hepatoma and MCF-7 breast carcinoma cells.

CONCLUSION

Effects of curcumin on cell growth and survival factor expression suggest its potential benefit in the treatment of cancer without a direct radiosensitizing influence of curcumin on these cells.

Choreographing couch and collimator in volumetric modulated arc therapy

PURPOSE

To design and optimize trajectory-based, noncoplanar subarcs for volumetric modulated arc therapy (VMAT) deliverable on both Varian TrueBEAM system and traditional accelerators; and to investigate their potential advantages for treating central nervous system (CNS) tumors.

METHODS AND MATERIALS

To guide the computerized selection of beam trajectories consisting of simultaneous couch, gantry, and collimator motion, a score function was implemented to estimate the geometric overlap between targets and organs at risk for each couch/gantry angle combination. An initial set of beam orientations is obtained as a function of couch and gantry angle, according to a minimum search of the score function excluding zones of collision. This set is grouped into multiple continuous and extended subarcs subject to mechanical limitations using a hierarchical clustering algorithm. After determination of couch/gantry trajectories, a principal component analysis finds the collimator angle at each beam orientation that minimizes residual target-organ at risk overlaps. An in-house VMAT optimization algorithm determines the optimal multileaf collimator position and monitor units for control points within each subarc. A retrospective study of 10 CNS patients compares the proposed method of VMAT trajectory with dynamic gantry, leaves, couch, and collimator motion (Tra-VMAT); a standard noncoplanar VMAT with no couch/collimator motion within subarcs (Std-VMAT); and noncoplanar intensity-modulated radiotherapy (IMRT) plans that were clinically used.

RESULTS

Tra-VMAT provided improved target dose conformality and lowered maximum dose to brainstem, optic nerves, and chiasm by 7.7%, 1.1%, 2.3%, and 1.7%, respectively, compared with Std-VMAT. Tra-VMAT provided higher planning target volume minimum dose and reduced maximum dose to chiasm, optic nerves, and cochlea by 6.2%, 1.3%, 6.3%, and 8.4%, respectively, and reduced cochlea mean dose by 8.7%, compared with IMRT. Tra-VMAT averaged beam-on time was comparable to Std-VMAT but significantly (45%) less than IMRT.

CONCLUSION

Optimized couch, gantry, and collimator trajectories may be integrated into VMAT with improved mechanical flexibility and may provide better dosimetric properties and improved efficiency in the treatment of CNS tumors.

Dosimetric analysis of modulated and hybrid arcs in stereotactic radiosurgery

PURPOSE

Forward-planned conformal arcs (termed dynamic arcs in the BrainLab iPlan system) have been routinely used in cranial stereotactic radiosurgery (SRS) for many yeras. This study compares dosimetric parameters of the newer, inversely-planned volumetric modulated arc therapy (VMAT) and VMAT-conformal hybrid plans with conformal arc plans. In the hybrid plans, various numbers of conformal arcs in a conformal plan are replaced with VMAT arcs.

METHODS

Ten brain cancer cases previously treated on a Novalis accelerator for frameless cranial stereotactic radiosurgery using conformal arcs generated by BrainLab iPlan treatment planning system were retrospectively studied with various numbers of VMAT arcs replacing the conformal arcs. Pure VMAT plans of different numbers of arcs were also generated using the same angle and arc length setup for all or part of the conformal arcs and compared with both the original and hybrid plans. Pinnacle version 9.0 was used for treatment plan generation. SmartArc was used for the VMAT planning for a Novalis accelerator. The conformity index (CI), defined as the ratio of the isodose volume to the isodose covered target volume, gradient index (GI), defined as the ratio of the 50% isodose volume (V₅₀) to the 100% isodose volume, volume covered by 12 Gy isodose (V₁₂), mean dose and standard deviation of dose in target were studied.

RESULTS

With one of the conformal arcs replaced with a VMAT arc of the same weighting and geometric setup, the average CI with one standard deviation was improved from 1.35 ± 0.18 to 1.29 ± 0.15 (p-value 0.03), while the average GI degraded from 3.8 ± 1.0 to 4.9 ± 1.5 (p-value < 0.01). The degraded GI in the VMAT plans is due to the absence of beam margin limit in SmartArc planning. Pure VMAT plans usually demonstrated better CI values than the hybrid and conformal arc plans when the number of arcs was greater than 2. The GI value was improved with increasing number of arcs in VMAT plans. For target volumes greater than 1 cc, VMAT plans demonstrated improved CI and smaller V₅₀ and V₁₂ than that in conformal arc plans. Better dose fall-off in normal tissue in VMAT plans is accompanied with higher dose heterogeneity in the target volume.

CONCLUSION

VMAT and conformal-VMAT hybrid plans usually offer better target conformity. The dose fall-off in normal tissue is also better in VMAT plans when the number of arcs is greater than 3 and target volume is greater than 1 cc, but compromise the dose homogeneity in target volumes. VMAT plans are the best option for targets that are greater than 1 cc for cranial radiosurgery treatments, while for very small targets, conformal arc technique may still be the better choice based on data of dose fall-off in normal tissues.

Application of volumetric modulated arc therapy (VMAT) in a dual-vendor environment

Background and Purpose

The purpose of this study was to assess plan quality and treatment time achievable with the new VMAT optimization tool implemented in the treatment planning system Oncentra MasterPlan^® as compared to IMRT for Elekta SynergyS^® linear accelerators.

Materials and methods

VMAT was implemented on a SynergyS^® linear accelerator (Elekta Ltd., Crawley, UK) with Mosaiq^® record and verify system (IMPAC Medical Systems, Sunnyvale, CA) and the treatment planning system Oncentra MasterPlan^® (Nucletron BV, Veenendaal, the Netherlands). VMAT planning was conducted for three typical target types of prostate cancer, hypopharynx/larynx cancer and vertebral metastases, and compared to standard IMRT with respect to plan quality, number of monitor units (MU), and treatment time.

Results

For prostate cancer and vertebral metastases single arc VMAT led to similar plan quality as compared to IMRT. For treatment of the hypopharynx/larynx cancer, a second arc was necessary to achieve sufficient plan quality. Treatment time was reduced in all cases to 35% to 43% as compared to IMRT. Times required for optimization and dose calculation, however, increased by a factor of 5.0 to 6.8.

Conclusion

Similar or improved plan quality can be achieved with VMAT as compared to IMRT at reduced treatment times but increased calculation times.

A RapidArc planning strategy for prostate with simultaneous integrated boost

Since the clinical implementation of novel rotational forms of intensity‐modulated radiotherapy, a variety of planning studies have been published that reinforce the major selling points of the technique. Namely, comparable or even improved dose distributions with a reduction in both monitor units and treatment times, when compared with static gantry intensity‐modulated radiotherapy. Although the data are promising, a rigorous approach to produce these plans has yet to be established. As a result, this study outlines a robust and streamlined planning strategy with a concentration on RapidArc class solutions for prostate with a simultaneous integrated boost. This planning strategy outlines the field setup, recommended starting objectives, required user interactions to be made throughout optimization and post‐optimization adjustments. A comparative planning study, with static gantry IMRT, is then presented as justification for the planning strategy itself. A variety of parameters are evaluated relating to both the planning itself (optimization and calculation time) and the plans that result. Results of this comparative study are in line with previously published data, and the planning process is streamlined to a point where the RapidArc optimization time takes 15±1.3 minutes. Application of this planning strategy reduces the dependence of the produced plan on the experience of the planner, and has the potential to streamline the planning process within radiotherapy departments.

PACS numbers: 87.55.x, 87.55.D, 87.55.de, 87.55.dk

Prospective phase II study of preoperative short-course radiotherapy for rectal cancer with twice daily fractions of 2.9 Gy to a total dose of 29 Gy--long-term results

Background

To evaluate clinical outcome after preoperative short-course radiotherapy for rectal cancer with twice daily fractions of 2.9 Gy to a total dose of 29 Gy and adjuvant chemotherapy for pathological stage UICC ≥ II.

Methods

118 patients (median age 64 years; male : female ratio 2.5 : 1) with pathological proven rectal cancer (clinical stage II 50%, III 41.5%, IV 8.5%) were treated preoperatively with twice daily radiotherapy of 2.9 Gy single fraction dose to a total dose of 29 Gy; surgery was performed immediately in the following week with total mesorectal excision (TME). Adjuvant 5-FU based chemotherapy was planned for pathological stage UICC ≥ II.

Results

After low anterior resection (70%) and abdominoperineal resection (30%), pathology showed stage UICC I (27.1%), II (25.4%), III (37.3%) and IV (9.3%). Perioperative mortality was 3.4% and perioperative complications were observed in 22.8% of the patients. Adjuvant chemotherapy was given in 75.3% of patients with pathological stage UICC ≥ II. After median follow-up of 46 months, five-year overall survival was 67%, cancer-specific survival 76%, local control 92% and freedom from systemic progression 75%. Late toxicity > grade II was observed in 11% of the patients.

Conclusions

Preoperative short-course radiotherapy, total mesorectal excision and adjuvant chemotherapy for pathological stage UICC ≥ II achieved excellent local control and favorable survival.