Consensus Statement Supporting the Presence of Onsite Radiation Oncology Departments at VHA Medical Centers.

Background: Although multiple studies demonstrate that radiotherapy is underused worldwide, the impact that onsite radiation oncology at medical centers has on the use of radiotherapy is poorly studied. The Veterans Health Administration (VHA) Palliative Radiotherapy Taskforce has evaluated the impact of onsite radiation therapy on the use of palliative radiation and has made recommendations based on these findings. Observations: Radiation consults and treatment occur in a more timely manner at VHA centers with onsite radiation therapy compared with VHA centers without onsite radiation oncology. Referring practitioners with onsite radiation oncology less frequently report difficulty contacting a radiation oncologist (0% vs 20%, respectively; P = .006) and patient travel (28% vs 71%, respectively; P < .001) as barriers to referral for palliative radiotherapy. Facilities with onsite radiation oncology are more likely to have multidisciplinary tumor boards (31% vs 3%, respectively; P = .11) and are more likely to be influenced by radiation oncology recommendations at tumor boards (69% vs 44%, respectively; P = .02). Conclusions: The VHA Palliative Radiotherapy Taskforce recommends the optimization of the use of radiotherapy within the VHA. Radiation oncology services should be maintained where present in the VHA, with consideration for expansion of services to additional facilities. Telehealth should be used to expedite consults and treatment. Hypofractionation should be used, when appropriate, to ease travel burden. Options for transportation services and onsite housing or hospitalization should be understood by treating physicians and offered to patients to mitigate barriers related to travel.

The Clinical Cell-Cycle Risk (CCR) Score Is Associated With Metastasis After Radiation Therapy and Provides Guidance on When to Forgo Combined Androgen Deprivation Therapy With Dose-Escalated Radiation.

PURPOSE: The clinical cell-cycle risk (CCR) score, which combines the University of California, San Francisco's Cancer of the Prostate Risk Assessment (CAPRA) and the cell cycle progression (CCP) molecular score, has been validated to be prognostic of disease progression for men with prostate cancer. This study evaluated the ability of the CCR score to prognosticate the risk of metastasis in men receiving dose-escalated radiation therapy (RT) with or without androgen deprivation therapy (ADT). METHODS AND MATERIALS: This retrospective, multi-institutional cohort study included men with localized National Comprehensive Cancer Network (NCCN) intermediate-, high-, and very high-risk prostate cancer (N = 741). Patients were treated with dose-escalated RT with or without ADT. The primary outcome was time to metastasis. RESULTS: The CCR score prognosticated metastasis with a hazard ratio (HR) per unit score of 2.22 (95% confidence interval [CI], 1.71-2.89; P < .001). The CCR score better prognosticated metastasis than NCCN risk group (CCR, P < .001; NCCN, P = .46), CAPRA score (CCR, P = .002; CAPRA, P = .59), or CCP score (CCR, P < .001; CCP, P = .59) alone. In bivariable analyses, CCR score remained highly prognostic when accounting for ADT versus no ADT (HR, 2.18; 95% CI, 1.61-2.96; P < .001), ADT duration as a continuous variable (HR, 2.11; 95% CI, 1.59-2.79; P < .001), or ADT given at or below the recommended duration for each NCCN risk group (HR, 2.19; 95% CI, 1.69-2.86; P < .001). Men with CCR scores below or above the multimodality threshold (CCR score, 2.112) had a 10-year risk of metastasis of 3.7% and 21.24%, respectively. Men with below-threshold scores receiving RT alone had a 10-year risk of metastasis of 3.7%, and for men receiving RT plus ADT, the 10-year risk of metastasis was also 3.7%. CONCLUSIONS: The CCR score accurately and precisely prognosticates metastasis and adds clinically actionable information relative to guideline-recommended therapies based on NCCN risk in men undergoing dose-escalated RT with or without ADT. For men with scores below the multimodality threshold, adding ADT may not significantly reduce their 10-year risk of metastasis.

Medical Mask Wearing During Treatment for Patients Undergoing Radiotherapy in COVID-19 Pandemic - An Experience of Protocol Setup and Dosimetric Evaluation for Particle/Proton Beam Therapy.

BACKGROUND: The coronavirus disease 2019 (COVID-19) pandemic has caused extreme challenges for the healthcare system. Medical masks have been proven to effectively block disease transmission. Radiotherapeutic departments are at unique risk for disease exposure with the repeated daily treatment schedule. A protocol of mask wearing during daily treatment was established, and the effect of wearing medical masks on dosimetry during proton beam therapy (PBT) was validated. METHODS: A department protocol of medical mask wearing was initiated after the COVID-19 pandemic. Medical masks that were made under standardized specification and regulation were obtained for analyses. The physical and dosimetric characteristics of these medical masks were measured by different proton energies using commercialized measurement tools. RESULTS: Patients and staff were able to adopt the protocol on a weekly basis, and no adverse events were reported. The average physical thickness of a single piece of medical mask was 0.5 mm with a water equivalent thickness (WET) of 0.1 mm. CONCLUSION: Our study revealed that mask wearing for patients undergoing daily radiotherapy is feasible and can provide basic protection for patients and staff. The impact of mask wearing on dosimetry was only 0.1 mm in WET, which has no impact on clinical PBT treatment. A medical mask-wearing policy can be applied safely without dosimetric concerns and should be considered as a standard practice for PBT centers during the COVID-19 pandemic.

Palliative Radiotherapy Within the Veterans Health Administration: Barriers to Referral and Timeliness of Treatment.

PURPOSE: Most Veterans Health Administration hospitals do not have radiation oncology (RO) departments on-site. The purpose of this study is to determine the impact of on-site RO on referral patterns and timeliness of palliative radiation therapy (PRT). MATERIALS AND METHODS: A survey was sent to medical directors at 149 Veterans Health Administration centers. Questions evaluated frequency of referral for PRT, timeliness of RO consults and treatment, and barriers to referral for PRT. Chi-square analysis was used to evaluate differences between centers that have on-site RO and centers that refer to outside facilities. RESULTS: Of 108 respondents, 33 (31%) have on-site RO. Chi-square analysis revealed that RO consult within 1 week is more likely at centers with on-site RO (68% v 31%; P = .01). Centers with on-site RO more frequently deliver PRT for spinal cord compression within 24 hours (94% v 70%; P = .01). Those without on-site RO were more likely to want increased radiation oncologist involvement (64% v 26%; P < .001). Barriers to referral for PRT included patient ability to travel (81%), patient noncompliance (31%), delays in consult and/or treatment (31%), difficulty contacting a radiation oncologist (14%), and concern regarding excessive number of treatments (13%). Respondents with on-site RO less frequently reported delays in consult and/or treatment (6% v 41%; P < .0001) and difficulty contacting a radiation oncologist (0% v 20%; P = .0056) as barriers. CONCLUSION: Respondents with on-site RO reported improved communication with radiation oncologists and more timely consultation and treatment initiation. Methods to improve timeliness of PRT for veterans at centers without on-site RO should be considered.

Dosimetric comparison between RapidArc and HyperArc techniques in salvage stereotactic body radiation therapy for recurrent nasopharyngeal carcinoma.

BACKGROUND: To evaluate dosimetric differences of salvage irradiations using two commercially available volumetric modulated arc therapy (VMAT) stereotactic body radiation therapy (SBRT) techniques: RapidArc (RA) and HyperArc (HA), for recurrent nasopharyngeal carcinoma (NPC) after initial radiation therapy. METHODS: Ten patients with recurrent NPC status previously treated with radiation therapy were considered suitable candidates for salvage SBRT using VMAT approach. Two separate treatment plans were created with HA and RA techniques for each case, with dosimetric outcomes compared with respect to tumor target coverage and organs-at-risk (OARs) sparing. Furthermore, the cumulative radiobiological effects to the relevant OARs from the original radiotherapy to the respective salvage SBRT plans were analyzed in terms of biologically effective dose (BED). RESULTS: Treatment with HA exhibited similar target dose coverage as with RA, while delivering a higher mean dose to the targets. Using RA technique, the mean maximal doses to optic apparatus and the mean brain dose were reduced by 1 to 1.5 Gy, comparing to HA technique. The conformity index, gradient radius, and intermediate dose spillage in HA plans were significantly better than those in RA. With HA technique, the volume of brain receiving 12 Gy or more was reduced by 44%, comparing to RA technique. The cumulative BEDs to spinal cord and optic apparatus with RA technique were 1 to 2 Gy3 less than those with HA. HA technique significantly reduced the volume within body that received more than 100 Gy. CONCLUSIONS: With better dose distribution than RA while maintaining sufficient target dose coverage, HA represents an attractive salvage SBRT technique for recurrent NPC.

Systemic and tumor-directed therapy for oligometastatic prostate cancer: study protocol for a phase II trial for veterans with de novo oligometastatic disease.

BACKGROUND: The treatment paradigm for metastatic hormone-sensitive prostate cancer (mHSPC) patients is evolving. PET/CT now offers improved sensitivity and accuracy in staging. Recent randomized trial data supports escalated hormone therapy, local primary tumor therapy, and metastasis-directed therapy. The impact of combining such therapies into a multimodal approach is unknown. This Phase II single-arm clinical trial sponsored and funded by Veterans Affairs combines local, metastasis-directed, and systemic therapies to durably render patients free of detectable disease off active therapy. METHODS: Patients with newly-diagnosed M1a/b prostate cancer (PSMA PET/CT staging is permitted) and 1-5 radiographically visible metastases (excluding pelvic lymph nodes) are undergoing local treatment with radical prostatectomy, limited duration systemic therapy for a total of six months (leuprolide, abiraterone acetate with prednisone, and apalutamide), metastasis-directed stereotactic body radiotherapy (SBRT), and post-operative fractionated radiotherapy if pT ≥ 3a, N1, or positive margins are present. The primary endpoint is the percent of patients achieving a serum PSA of < 0.05 ng/mL six months after recovery of serum testosterone ≥150 ng/dL. Secondary endpoints include time to biochemical progression, time to radiographic progression, time to initiation of alternative antineoplastic therapy, prostate cancer specific survival, health related quality-of-life, safety and tolerability. DISCUSSION: To our knowledge, this is the first trial that tests a comprehensive systemic and tumor directed therapeutic strategy for patients with newly diagnosed oligometastatic prostate cancer. This trial, and others like it, represent the critical first step towards curative intent therapy for a patient population where palliation has been the norm. TRIAL REGISTRATION: Clinicaltrials.gov identifier: NCT03298087 (registration date: September 29, 2017).

Treatment outcomes with whole-field versus split-field intensity-modulated radiotherapy for patients with nasopharyngeal carcinoma.

BACKGROUND: The purpose of this study was to present our comparison of the clinical outcome of patients with nasopharyngeal carcinoma (NPC) treated with whole-field intensity-modulated radiotherapy (whole-field-IMRT) or split-field-IMRT. METHODS: We retrospectively studied 388 patients with M0 NPC. The median lower neck doses were 50 Gy in 1.35 Gy/fractions for the 240 whole-field-IMRT patients, and 50.4 Gy in 1.8 to 2.0 Gy/fractions for the 148 split-field-IMRT patients. RESULTS: The IMRT technique did not affect the overall survival (OS; P = .077) and locoregional control (P = .231) rates. However, the split-field-IMRT group had more locoregional recurrences at the whole neck (P = .005) but not at the nasopharynx (P = .968) or the lower neck (P = .485). The patients treated with split-field-IMRT (43.2%) had more grade III neck fibrosis than the patients who received whole-field-IMRT (18.3%; P < .001). Only 1 patient had temporal lobe necrosis in our study. CONCLUSION: Our study shows that whole-field-IMRT using a lower dose/fraction for the lower neck results in at least comparable locoregional control and less fibrosis compared to conventional fraction with split-field-IMRT.

Postradiation hypothyroidism in head and neck cancers: A Department of Veterans Affairs single-institution case-control dosimetry study.

We performed a case-control study to characterize the dose-volume relationship and other variables leading to hypothyroidism after head and neck (H&N) cancer radiation therapy (RT) in a homogenous Veterans Affairs (VA) population. All records of patients receiving RT for various H&N cancers at a single VA medical center between 2007 and 2013 (n = 143) were screened for post-RT thyroid stimulating hormone (TSH) levels (n = 77). The thyroid gland was contoured on each slice of the planning computed tomography scan when available (hypothyroid: n = 18; euthyroid > 2 years: n = 16), and dose-volume histograms based on physical dose and biologically equivalent dose (BED) were compared systematically to find the significant dose-volume thresholds that distinguish the patients who developed clinical hypothyroidism. Dosimetric and clinical variables were considered in univariate and multivariate analysis. Preirradiation prevalence of hypothyroidism was 8 of 143 (5.6%). After RT, 36 of 77 (47%) screened patients had abnormally high TSH, of which 22 of 36 (61%) had clinical hypothyroidism after 1.29 ± 0.99 years. The median follow-up durations were 3.3 years and 4.7 years for euthyroid and hypothyroid patients, respectively. Compared with the euthyroid cohort (n = 41), these hypothyroid patients displayed no significant difference in age, gender, primary tumor site, thyroid volume, hypertension, diabetes, or use of chemotherapy, surgery, or intensity-modulated radiation therapy (IMRT). They were more likely to have had stage 3 or 4 cancer than euthyroid patients (86.5% vs 73.2%, p = 0.01). The odds ratios of hypothyroidism for stage 3 + 4 cancers and V50Gy < 75% were 5.0 and 0.2, respectively (p < 0.05). Equivalent BED threshold of V75Gy3 < 75% gave an odds ratio of 0.156 for developing hypothyroidism (p = 0.02). The prevalence of post-RT clinical hypothyroidism was relatively high for patients with H&N cancers and warrants routine surveillance, especially in those with higher stage malignancy. V50Gy < 75% may be a useful guideline to avoid hypothyroidism. We also show BED data which could be used for unconventionally fractionated schemes, and V75Gy3 < 75% may be a useful guideline.

Patterns of failure after postoperative intensity-modulated radiotherapy for locally advanced buccal cancer: Initial masticator space involvement is the key factor of recurrence.

BACKGROUND: The purpose of this study was to determine failure patterns and clinicopathologic prognostic factors in patients with locally advanced buccal cancer after postoperative intensity-modulated radiotherapy (IMRT). METHODS: Eighty-two patients with locally advanced (American Joint Committee on Cancer [AJCC] stage III/IV) buccal cancer who underwent surgery followed by postoperative IMRT between January 2007 and October 2012 were retrospectively analyzed. RESULTS: Eighteen patients had local recurrences as the first recurrent site and 11 had supramandibular notch recurrences; the majority of recurrences were classified as marginal failures. The median time from the first local or regional recurrence to death was 5.9 months. In multivariate analyses of survivals, the initial masticator space involvement was the most important prognostic factor. Masticator space involvement, N classification, and maxillectomy were the significant prognostic predictors for supramandibular notch recurrences. CONCLUSION: Postoperative IMRT for buccal cancer should not include the surgical beds alone, rather, it should be based on the potential patterns of spread.

Dose escalation via brachytherapy boost for nasopharyngeal carcinoma in the era of intensity-modulated radiation therapy and combined chemotherapy.

To investigate if dose escalation using intracavitary brachytherapy (ICBT) improves local control for nasopharyngeal carcinoma (NPC) in the era of intensity-modulated radiation therapy (IMRT) and concurrent chemoradiation treatment (CCRT). We retrospectively analyzed 232 patients with Stage T1-3 N0-3 M0 NPC who underwent definitive IMRT with or without additional ICBT boost between 2002 and 2013. For most of the 124 patients who had ICBT boost, the additional brachytherapy was given as 6 Gy in 2 fractions completed within 1 week after IMRT of 70 Gy. CCRT with or without adjuvant chemotherapy was used for 176 patients, including 88 with and 88 without ICBT boost, respectively. The mean follow-up time was 63.1 months. The 5-year overall survival and local control rates were 81.5% and 91.5%, respectively. ICBT was not associated with local control prediction (P = 0.228). However, in a subgroup analysis, 75 T1 patients with ICBT boost had significantly better local control than the other 71 T1 patients without ICBT boost (98.1% vs 85.9%, P = 0.020), despite having fewer patients who had undergone chemotherapy (60.0% vs 76.1%, P = 0.038). Multivariate analysis showed that both ICBT (P = 0.029) and chemotherapy (P = 0.047) influenced local control for T1 patients. Our study demonstrated that dose escalation with ICBT can improve local control of the primary tumor for NPC patients with T1 disease treated with IMRT, even without chemotherapy.

Dosimetric and radiobiological comparison of Cyberknife and Tomotherapy in stereotactic body radiotherapy for localized prostate cancer.

BACKGROUND AND PURPOSE: As recent studies have suggested relatively low α/ß for prostate cancer, the interest in hypofractionated stereotactic body radiotherapy (SBRT) for prostate cancer is rising. The aim of this study is to compare dosimetric results of Cyberknife (CK) with Tomotherapy (HT) in SBRT for localized prostate cancer. Furthermore, the radiobiologic consequences of heterogeneous dose distribution are also analyzed. MATERIAL AND METHOD: A total of 12 cases of localized prostate cancer previously treated with SBRT were collected. Treatments had been planned and delivered using CK. Then HT plans were generated for comparison afterwards. The prescribed dose was 37.5Gy in 5 fractions. Dosimetric indices for target volumes and organs at risk (OAR) were compared. For radiobiological evaluation, generalized equivalent uniform dose (gEUD) and normal tissue complication probability (NTCP) were calculated and compared. RESULT: Both CK and HT achieved target coverage while meeting OAR constraints adequately. HT plans resulted in better dose homogeneity (Homogeneity index: 1.04±0.01 vs. 1.21±0.01; p = 0.0022), target coverage (97.74±0.86% vs. 96.56±1.17%; p = 0.0076) and conformity (new vonformity index: 1.16±0.05 vs. 1.21±0.04; p = 0.0096). HT was shown to predict lower late rectal toxicity as compared to CK. Integral dose to body was also significantly lower in HT plans (46.59±6.44 Gy'L vs 57.05±11.68 Gy'L; p = 0.0029). CONCLUSION: Based on physical dosimetry and radiobiologic considerations, HT may have advantages over CK, specifically in rectal sparing which could translate into clinical benefit of decreased late toxicities.

Bone mineral density loss in thoracic and lumbar vertebrae following radiation for abdominal cancers.

PURPOSE: To investigate the relationship between abdominal chemoradiation (CRT) for locally advanced cancers and bone mineral density (BMD) reduction in the vertebral spine. MATERIALS AND METHODS: Data from 272 patients who underwent abdominal radiation therapy from January 1997 to May 2015 were retrospectively reviewed. Forty-two patients received computed tomography (CT) scans of the abdomen prior to initiation and at least twice after radiation therapy. Bone attenuation (in Hounsfield unit) (HU) measurements were collected for each vertebral level from T7 to L5 using sagittal CT images. Radiation point dose was obtained at each mid-vertebral body from the radiation treatment plan. Percent change in bone attenuation (Δ%HU) between baseline and post-radiation therapy were computed for each vertebral body. The Δ%HU was compared against radiation dose using Pearson's linear correlation. RESULTS: Abdominal radiotherapy caused significant reduction in vertebral BMD as measured by HU. Patients who received only chemotherapy did not show changes in their BMD in this study. The Δ%HU was significantly correlated with the radiation point dose to the vertebral body (R=-0.472, P<0.001) within 4-8 months following RT. The same relationship persisted in subsequent follow up scans 9 months following RT (R=-0.578, P<0.001). Based on the result of linear regression, 5 Gy, 15 Gy, 25 Gy, 35 Gy, and 45 Gy caused 21.7%, 31.1%, 40.5%, 49.9%, and 59.3% decrease in HU following RT, respectively. Our generalized linear model showed that pre-RT HU had a positive effect (ß=0.830) on determining post-RT HU, while number of months post RT (ß=-0.213) and radiation point dose (ß=-1.475) had a negative effect. A comparison of the predicted versus actual HU showed significant correlation (R=0.883, P<0.001) with the slope of the best linear fit=0.81. Our model's predicted HU were within ±20 HU of the actual value in 53% of cases, 70% of the predictions were within ±30 HU, 81% were within ±40 HU, and 90% were within ±50 HU of the actual post-RT HU. Four of 42 patients were found to have vertebral body compression fractures in the field of radiation. CONCLUSIONS: Patients who receive abdominal chemoradiation develop significant BMD loss in the thoracic and lumbar vertebrae. Treatment-related BMD loss may contribute to the development of vertebral compression fractures. A predictive model for post-CRT BMD changes may inform bone protective strategies in patients planned for abdominal CRT.

Dosimetric distribution to tooth-bearing areas in intensity-modulated radiation therapy for head and neck cancer: a pilot study.

OBJECTIVES: Dosimetric distribution of intensity-modulated radiotherapy (IMRT) to tooth-bearing areas for common head and neck (H&N) cancer sites were analyzed to facilitate minimization of osteoradionecrosis (ORN) risk through preradiation dental treatment planning. STUDY DESIGN: Fifty-four patients received IMRT with prescribed doses ranging from 6000 centigrays (cGy) (adjuvant) to 6930 cGy (primary) to treat base of tongue (BOT), tonsil, larynx, nasopharynx, and hypopharynx cancers. The average maximal radiation dose delivered was recorded in tooth-bearing areas (anteriors, premolars, and first, second, and third molars) of the maxilla and mandible. RESULTS: All tooth-bearing areas in laryngeal cancer cases received less than 2500 cGy. Maxillary and mandibular molar regions for BOT, tonsil, and hypopharynx cancers received 5000 cGy or higher. In nasopharynx cancers, maxillary teeth received higher doses than mandibular teeth. CONCLUSIONS: Among 5 H&N subsites, mandibular molar regions for BOT, tonsil, and hypopharynx cancers received higher IMRT doses on average, posing the greatest ORN risk.

Visual Acuity, Contrast Sensitivity and Color Vision Three Years After Iodine-125 Brachytherapy for Choroidal and Ciliary Body Melanoma.

PURPOSE: To report visual acuity, contrast sensitivity and color vision prior to, 1 year after, 2 years after and 3 years after iodine-125 brachytherapy for choroidal and ciliary body melanoma (CCM). DESIGN: Prospective interventional case series. PARTICIPANTS: Thirty-seven patients (37 eyes) with CCM. METHODS: Patients had best-corrected Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity, Pelli-Robson contrast sensitivity and Hardy-Rand-Rittler color vision measurement; comprehensive ophthalmology examination; optical coherence tomography; and ultrasonography at baseline prior to, 1 year after, 2 years after and 3 years after I-125 brachytherapy. MAIN OUTCOME MEASURES: Visual acuity, contrast sensitivity and color vision prior to, 1 year after, 2 years after and 3 years after brachytherapy. RESULTS: Nineteen (19) men and 18 women with mean age of 58 years (SD 13, range 30-78) prior to, 1 year after, 2 years after and 3 years after brachytherapy had mean best-corrected visual acuity of 77 letters (20/32), 65 letters (20/50), 56 letters (20/80) and 47 letters (20/125); contrast sensitivity of 30, 26, 22 and 19 letters; color vision of 26, 20, 17 and 14 test figures, respectively. Decrease in visual acuity, contrast sensitivity and color vision was statistically significant from baseline at 1 year, 2 years, and 3 years after brachytherapy. Decreased acuity at 3 years was associated with mid-choroid and macula melanoma location, ≥ 4.1 mm melanoma height, radiation maculopathy and radiation optic neuropathy. CONCLUSION: 1, 2 and 3 years after brachytherapy, eyes with CCM had significantly decreased visual acuity, contrast sensitivity and color vision.

The impact of reduced-volume, intensity-modulated radiation therapy on disease control in nasopharyngeal carcinoma.

OBJECTIVE: To investigate the feasibility of using intensity-modulated radiotherapy (IMRT) with reduced, high-dose target volumes for nasopharyngeal carcinoma (NPC). METHODS: The first 57 patients (admitted from October 2005 to May 2008) were treated with large-target-volume IMRT (LV-IMRT). For the LV-IMRT group, the CTV at 70 Gy (CTV70) was delineated as the gross target volume (GTV) plus 7mm, with or without the first-echelon lymph-node region. The next 56 patients (admitted from June 2008 to November 2011) were treated with reduced-target-volume IMRT (RV-IMRT). For the RV-IMRT group, the CTV70 was delineated as the GTV alone. RESULTS: The 4-year local recurrence-free, regional recurrence-free, distant metastasis-free, progression-free, and overall survival rates were 77.2%, 80.1%, 83.2%, 61.2%, and 74.4% for the LV-IMRT group and 83.5%, 92.6%, 89.1%, 78.5, and 91.0% for the RV-IMRT group, respectively. Late toxicity scoring of xerostomia was lesser in the RV-IMRT group than the LV-IMRT group (P < 0.001). CONCLUSIONS: The use of RV-IMRT for the treatment of NPC did not negatively affect survival rates but did reduce the late xerostomia events compared to LV-IMRT.

Near Real-Time Assessment of Anatomic and Dosimetric Variations for Head and Neck Radiation Therapy via Graphics Processing Unit-based Dose Deformation Framework.

PURPOSE: The purpose of this study was to systematically monitor anatomic variations and their dosimetric consequences during intensity modulated radiation therapy (IMRT) for head and neck (H&N) cancer by using a graphics processing unit (GPU)-based deformable image registration (DIR) framework. METHODS AND MATERIALS: Eleven IMRT H&N patients undergoing IMRT with daily megavoltage computed tomography (CT) and weekly kilovoltage CT (kVCT) scans were included in this analysis. Pretreatment kVCTs were automatically registered with their corresponding planning CTs through a GPU-based DIR framework. The deformation of each contoured structure in the H&N region was computed to account for nonrigid change in the patient setup. The Jacobian determinant of the planning target volumes and the surrounding critical structures were used to quantify anatomical volume changes. The actual delivered dose was calculated accounting for the organ deformation. The dose distribution uncertainties due to registration errors were estimated using a landmark-based gamma evaluation. RESULTS: Dramatic interfractional anatomic changes were observed. During the treatment course of 6 to 7 weeks, the parotid gland volumes changed up to 34.7%, and the center-of-mass displacement of the 2 parotid glands varied in the range of 0.9 to 8.8 mm. For the primary treatment volume, the cumulative minimum and mean and equivalent uniform doses assessed by the weekly kVCTs were lower than the planned doses by up to 14.9% (P=.14), 2% (P=.39), and 7.3% (P=.05), respectively. The cumulative mean doses were significantly higher than the planned dose for the left parotid (P=.03) and right parotid glands (P=.006). The computation including DIR and dose accumulation was ultrafast (∼45 seconds) with registration accuracy at the subvoxel level. CONCLUSIONS: A systematic analysis of anatomic variations in the H&N region and their dosimetric consequences is critical in improving treatment efficacy. Nearly real-time assessment of anatomic and dosimetric variations is feasible using the GPU-based DIR framework. Clinical implementation of this technology may enable timely plan adaptation and improved outcome.

Dependence of achievable plan quality on treatment technique and planning goal refinement: a head-and-neck intensity modulated radiation therapy application.

PURPOSE: To develop a practical workflow for retrospectively analyzing target and normal tissue dose-volume endpoints for various intensity modulated radiation therapy (IMRT) delivery techniques; to develop technique-specific planning goals to improve plan consistency and quality when feasible. METHODS AND MATERIALS: A total of 165 consecutive head-and-neck patients from our patient registry were selected and retrospectively analyzed. All IMRT plans were generated using the same dose-volume guidelines for TomoTherapy (Tomo, Accuray), TrueBeam (TB, Varian) using fixed-field IMRT (TB_IMRT) or RAPIDARC (TB_RAPIDARC), or Siemens Oncor (Siemens_IMRT, Siemens). A MATLAB-based dose-volume extraction and analysis tool was developed to export dosimetric endpoints for each patient. With a fair stratification of patient cohort, the variation of achieved dosimetric endpoints was analyzed among different treatment techniques. Upon identification of statistically significant variations, technique-specific planning goals were derived from dynamically accumulated institutional data. RESULTS: Retrospective analysis showed that although all techniques yielded comparable target coverage, the doses to the critical structures differed. The maximum cord doses were 34.1 ± 2.6, 42.7 ± 2.1, 43.3 ± 2.0, and 45.1 ± 1.6 Gy for Tomo, TB_IMRT, TB_RAPIDARC, and Siemens_IMRT plans, respectively. Analyses of variance showed significant differences for the maximum cord doses but no significant differences for other selected structures among the investigated IMRT delivery techniques. Subsequently, a refined technique-specific dose-volume guideline for maximum cord dose was derived at a confidence level of 95%. The dosimetric plans that failed the refined technique-specific planning goals were reoptimized according to the refined constraints. We observed better cord sparing with minimal variations for the target coverage and other organ at risk sparing for the Tomo cases, and higher parotid doses for C-arm linear accelerator-based IMRT and RAPIDARC plans. CONCLUSION: Patient registry-based processes allowed easy and systematic dosimetric assessment of treatment plan quality and consistency. Our analysis revealed the dependence of certain dosimetric endpoints on the treatment techniques. Technique-specific refinement of planning goals may lead to improvement in plan consistency and plan quality.

Ureteral stent insertion for gynecologic interstitial high-dose-rate brachytherapy.

PURPOSE: To determine the utility of ureteral stents in interstitial gynecological brachytherapy. METHODS AND MATERIALS: We reviewed 289 patients with cervix cancer treated with high-dose-rate interstitial brachytherapy who did not have pretreatment hydronephrosis to determine the relative incidence of benign ureteral strictures after treatment. We also did comparative dosimetry analysis in five cases of high-dose-rate brachytherapy. Bilateral ureteral stents were placed during the procedure. Three dosimetry plans were created to determine the impact of modifying clinical target volume (CTV) and applying ureteral dose constraints. In Plan 1, the ureters were contoured and excluded from the CTV and 120% dose constraints were applied. In Plan 2, the ureters were contoured and excluded, but no dose constraints were applied to the ureter. In Plan 3, the CTV was created as if the location of the ureters was unknown and then ureteral dose was determined. RESULTS: There were 11 ureteral strictures observed in 255 nonstented cases and 0 ureteral strictures in 34 stented cases. Plan 1 reduced the ureter dose (D(0.1cc)) by a median 22% (7.0-53.8%) compared with Plan 2 and by a median of 30.9% (12.3-65%). compared with Plan 3. CONCLUSIONS: Placement of stents and ureteral dose constraints facilitates dosimetry and reduces the dose to ureters. Temporary ureteral stents prevent obstruction during interstitial gynecologic brachytherapy and allows the ureters to be addressed as an organ at risk.