Head and Neck Cancer Patient Population, Management, and Oncologic Outcomes from the COVID-19 Pandemic

The COVID-19 pandemic precipitated drastic changes in cancer care. Its impact on the U.S. head and neck cancer population has yet to be fully understood. This study aims to understand the impact of pandemic-related changes on the head and neck cancer population. An observational study of head and neck cancer patients at a single institution during the spring of 2020 and 2019 was performed. Clinical characteristics and survival outcomes were analyzed. In 2020, 54 head and neck cancer patients were evaluated in the department of radiation oncology vs. 74 patients seen in 2019; 42% of the patients were female in 2019 versus 24% in 2020 (p = 0.036). The median follow-up time was 19.4 and 31 months for 2020 and 2019, respectively. After adjusting for stage, the relapse-free survival probability at 6 and 12 months was 79% and 69% in 2020 vs. 96% and 89% in 2019, respectively (p = 0.036). There was no significant difference in the overall survival, with 94% and 89% in 2020 and 2019, respectively (p = 0.61). Twenty-one percent of patients received induction chemotherapy in 2020 versus 5% in 2019 (p = 0.011); significantly more treatment incompletions occurred in 2020, 9% vs. 0% in 2019 (p = 0.012). Moreover, the stage-adjusted RFS differed between cohorts, suggesting head and neck cancer patients seen during the initial wave of COVID-19 may experience worse oncologic outcomes.

Tracking and Reducing SF6 Usage in Radiation Oncology: A Step Toward Net-Zero Health Care Emissions

Sulfur hexafluoride (SF6) is a widely used insulating gas in medical linear accelerators (LINACs) due to its high dielectric strength, heat transfer capabilities, and chemical stability. However, its long lifespan and high Global Warming Potential (GWP) make it a significant contributor to the environmental impact of radiation oncology. SF6 has an atmospheric lifespan of 3200 years and a GWP 23,000 times that of carbon dioxide. The amount of SF6 that can be emitted through leakage from machines is also concerning. It is estimated that the approximate 15,042 LINACs globally may leak up to 64,884,185.9 carbon dioxide equivalent per year, which is the equivalent greenhouse gas emissions of 13,981 gasoline-powered passenger vehicles driven for 1 year. Despite being regulated as a greenhouse gas under the United Nations Framework Convention on Climate Change, SF6 use within health care is often exempt from regulation, and only a few states in the United States have specific SF6 management regulations. This article highlights the need for radiation oncology centers and LINAC manufacturers to take responsibility for minimizing SF6 emissions. Programs that track usage and disposal, conduct life-cycle assessments, and implement leakage detection can help identify SF6 sources and promote recovery and recycling. Manufacturers are investing in research and development to identify alternative gases, improve leak detection, and minimize SF6 gas leakage during operation and maintenance. Alternative gases with lower GWP, such as nitrogen, compressed air, and perfluoropropane, may be considered as replacements for SF6; however, more research is needed to evaluate their feasibility and performance in radiation oncology. The article emphasizes the need for all sectors, including health care, to reduce their emissions to meet the goals of the Paris Agreement and ensure the sustainability of health care and our patients. Although SF6 is practical in radiation oncology, its environmental impact and contribution to the climate crisis cannot be ignored. Radiation oncology centers and manufacturers must take responsibility for reducing SF6 emissions by implementing best practices and promoting research and development around alternatives. To meet global emissions reduction goals and protect both planetary and patient health, the reduction of SF6 emissions will be essential.

Improved safety and quality in intravascular brachytherapy: A multi-institutional study using failure modes and effects analysis

PURPOSE

Highlight safety considerations in intravascular brachytherapy (IVBT) programs, provide relevant quality assurance (QA) and safety measures, and establish their effectiveness.

METHODS AND MATERIALS

Radiation oncologists, medical physicists, and cardiologists from three institutions performed a failure modes and effects analysis (FMEA) on the radiation delivery portion of IVBT. We identified 40 failure modes and rated the severity, occurrence, and detectability before and after consideration of safety practices. Risk priority numbers (RPN) and relative risk rankings were determined, and a sample QA safety checklist was developed.

RESULTS

We developed a process map based on multi-institutional consensus. Highest-RPN failure modes were due to incorrect source train length, incorrect vessel diameter, and missing prior radiation history. Based on these, we proposed QA and safety measures: ten of which were not previously recommended. These measures improved occurrence and detectability: reducing the average RPN from 116 to 58 and median from 84 to 40. Importantly, the average RPN of the top 10% of failure modes reduced from 311 to 172. With QA considered, the highest risk failure modes were from contamination and incorrect source train length.

CONCLUSIONS

We identified several high-risk failure modes in IVBT procedures and practical safety and QA measures to address them.

Premature discontinuation of curative radiation therapy: Insights from head and neck irradiation

Purpose

Factors related to premature discontinuation of curative radiation therapy (PDCRT) are understudied. This study aimed to examine causes and clinical outcomes of PDCRT at our institution by investigating the most common anatomical site associated with PDCRT.

Methods and materials

Among the 161 patients with PDCRT of various anatomic sites at our institution between 2010 and 2017, 36% received radiation to the head and neck region. Pertinent demographic, clinical, and treatment-related data on these 58 patients were collected. Survival was examined using the life-table method and log-rank test.

Results

The majority of patients were male (81%), white (67%), ≥60 years old (59%), living ≥10 miles away from the hospital (60%), single (57%), with Eastern Cooperative Oncology Group score ≥1 (86%), experiencing significant pain issues (67%), and had treatment interruptions in radiation therapy (RT; 66%). The most common reasons for PDCRT were discontinuation against medical advice (33%), medical comorbidity (24%), and RT toxicity (17%). Of the comorbidities leading to PDCRT, 50% was acute cardiopulmonary issues and 43% was infection. The mean follow-up time was 15.9 months, and the 2-year overall survival and disease-specific survival rates were 61% and 78%, respectively. Patients with illicit substance abuse, cardiovascular disease, and Eastern Cooperative Oncology Group score ≥2 had worse survival. A trend toward improved survival with total completed dose ≥50 Gy versus <50 Gy existed (74% versus 44%, respectively; P = .07).

Conclusions

In this largest-to-date, modern analysis of PDCRT, the most common cause of discontinuation was discontinuation against medical advice, which underscores the importance of patient education, optimization of RT symptoms, involvement of social work, and integration of other supportive services early in treatment. Survival remains suboptimal after PDCRT for H&N tumors, with a 2-year overall survival rate of 61%. Completing >50 Gy appears to confer a relative therapeutic benefit.

Computed tomography-based treatment planning for high-dose-rate brachytherapy using the tandem and ring applicator: influence of applicator choice on organ dose and inter-fraction adaptive planning

Three dimensional planning for high-dose-rate (HDR) brachytherapy in cervical cancer has been highly recommended by consensus guidelines such as the American Brachytherapy Society (ABS) and the Groupe Européen de Curiethérapie - European Society for Radiotherapy and Oncology (GEC-ESTRO). In this document, we describe our experience with computed tomography (CT)-based planning using the tandem/ring applicator. We discuss the influence of applicator geometry on doses to organs at risk (OARs), namely the bladder, rectum, and sigmoid. Through example cases with dose prescribed to point A, we demonstrate how adaptive planning can help achieve constraints to the OARs as per guidelines.

Long-term outcomes of acromegaly treated with fractionated stereotactic radiation: case series and literature review

Background

Growth hormone (GH)-secreting pituitary adenomas represent an uncommon subset of pituitary neoplasms. Stereotactic radiosurgery (SRS) and fractionated stereotactic radiotherapy (FSRT) have been used as primary or adjuvant treatment. The purpose of this study is to report the long-term tumor control and toxicity from our institution and to perform a systematic literature review of acromegaly patients treated with FSRT.

Methods

We retrospectively reviewed all patients treated with FSRT (median dose 50.4 Gray [Gy], range 50.4-54 Gy) between 2005 and 2012 who had: 1) GH-secreting adenoma with persistently elevated insulin growth factor-1 (IGF-1) despite medical therapy and 2) clinical follow up >3 years after FSRT. Patients were treated with modern FSRT planning techniques. Biochemical control was defined as IGF-1 normalization. Systematic review of the literature was performed for FSRT in acromegaly.

Results

With a median follow-up of 80 months, radiographic control was achieved in all 11 patients and overall survival was 100%. Long-term biochemical control was achieved in 10 patients (90.9%) with either FSRT alone (36.4%) or FSRT with continued medical management (45.5%). No patient experienced new hypopituitarism, cranial nerve dysfunctions, or visual deficits. Our systematic review found published rates of biochemical control and hypopituitarism vary, with uniformly good radiographic control and low incidence of visual changes.

Conclusions

Adjuvant FSRT offered effective long-term biochemical control and radiographic control, and there was a lower rate of complications in this current series. Review of the literature shows variations in published rates of biochemical control after FSRT for acromegaly, but low incidence of serious toxicities.

Low-dose cranial boost in high-risk adult acute lymphoblastic leukemia patients undergoing bone marrow transplant

PURPOSE

Acute lymphoblastic leukemia (ALL) has a predilection for CNS involvement. Patients with high-risk ALL are often managed with transplant using a radiation-based conditioning regimen. Historically, a high-dose prophylactic cranial boost (CB) of ≥12 Gy was given to reduce risk of central nervous system (CNS) recurrence. However, the use of CB has fallen out of favor because of toxicity concerns. In high-risk adults undergoing transplant at our institution, we have used a low-dose 6 Gy CB to reduce toxicity while conditioning adults with fully developed brains. The safety, efficacy, and utility of a low-dose CB in adults are poorly studied; herein, we report their outcomes and toxicity.

METHODS AND MATERIALS

We identified all high-risk ALL patients undergoing total body irradiation as part of their conditioning regimen. Those who received 6 Gy CB or no CB were included (55 total). Their charts were reviewed and statistical analyses were completed with R, version 2.15.2.

RESULTS

In patients undergoing CB, 3-year CNS disease-free survival and overall survival were 94.7% and 62.7%. In those not undergoing CBs, survivals were 81.8% and 51.5%. Notably, within the CB cohort, patients without prior CNS involvement had no CNS failures. In contrast, in the non-CB cohort, there were 2 CNS failures in patients with no history of CNS involvement. In the CB cohort, the only notable acute toxicity was parotitis (2.8%). Late toxicity in the CB cohort included 1 instance of cataracts (2.8%) without any evidence of cognitive impairment or potential radiation induced secondary malignancy.

CONCLUSIONS

A dose of 6 Gy CB is well-tolerated in the adult ALL population as part of a radiation-based conditioning regimen. Low-dose CB may be considered in adult patients with high-risk ALL without prior CNS involvement to reduce the likelihood of recurrence.

Intracoronary brachytherapy for in-stent restenosis of drug-eluting stents

PURPOSE

Given the limited salvage options for in-stent restenosis (ISR) of drug-eluting stents (DES), our high-volume cardiac catheterization laboratory has been performing intracoronary brachytherapy (ICBT) in patients with recurrent ISR of DES. This study analyzes their baseline characteristics and assesses the safety/toxicity of ICBT in this high-risk population.

METHODS AND MATERIALS

A retrospective analysis of patients treated with ICBT between September 2012 and December 2014 was performed. Patients with ISR twice in a single location were eligible. Procedural complications included vessel dissection, perforation, tamponade, slow/absent blood flow, and vessel closure. Postprocedural events included myocardial infarction, coronary artery bypass graft, congestive heart failure, stroke, bleeding, thrombosis, embolism, dissection, dialysis, or death occurring within 72 hours. A control group of patients with 2 episodes of ISR at 1 location who underwent percutaneous coronary intervention without ICBT was identified. Unpaired t tests and χ2 tests were used to compare the groups.

RESULTS

There were 134 (78%) patients in the ICBT group with 141 treated lesions and 37 (22%) patients in the control group. There was a high prevalence of hyperlipidemia (>95%), hypertension (>95%), and diabetes (>50%) in both groups. The groups were well-balanced with respect to age, sex, and pre-existing medical conditions, with the exception of previous coronary artery bypass graft being more common the ICBT group. Procedural complication rates were low in the control and ICBT groups (0% vs 4.5%, P = .190). Postprocedural event rates were low (<5%) in both groups. Readmission rate at 30 days was 3.7% in the ICBT group and 5.4% in the control group (P = .649).

CONCLUSIONS

This is the largest recent known series looking at ICBT for recurrent ISR of DES. ICBT is a safe treatment option with similarly low rates (<5%) of procedural and postprocedural complications compared with percutaneous coronary intervention alone. This study establishes the safety of ICBT in a high-risk patient cohort.

Microdosimetric characteristics of 50 kV X rays at different depths for breast intraoperative radiotherapy

An intraoperative radiation therapy (IORT) device with 50 kV X rays was designed to deliver a single dose to the tumour bed after local excision of breast cancer. The quality of a radiation can be determined by the microscopic distribution of energy transfers along and across the charged particle tracks. The lineal energy, y, serves as an accurate measure of local energy concentration. The dose mean lineal energy, yD, is an indicator of radiation quality. For low linear energy transfer radiation, the ratio of its dose mean lineal energy to that of (60)Co gamma rays can serve as a good indicator of the relative biological effectiveness (RBE) at low doses. In this study, microdosimetric simulations are performed for soft tissue irradiated by 50 kV X rays generated from the IORT device, with a 4-cm breast applicator attached. All energy transfers are recorded with the location coordinates in the tissue. Microdosimetric single events in a sphere of 1 µm in diameter are scored as a function of radial distances from the applicator surface. Single-event spectra are then constructed. From those single-event spectra, dose mean lineal energy is calculated. Compared with dose mean lineal energy of (60)Co gamma rays, the estimated RBEs at low doses are given for the X rays at different depths in the tissue. The RBEs at clinically relevant doses, as a function of depth, are also presented.

A Feasibility Study of Tumor Motion Estimate With Regional Deformable Registration Method for 4-Dimensional Radiation Therapy of Lung Cancer

This study aims to employ 4-dimensional computed tomography to quantify intrafractional tumor motion for patients with lung cancer to improve target localization in radiation therapy. A multistage regional deformable registration was implemented to calculate the excursion of gross tumor volume (GTV) during a breathing cycle. GTV was initially delineated on 0% phase of 4-dimensional computed tomography manually, and a subregion with 20 mm margin supplemented to GTV was generated with Eclipse treatment planning system (Varian Medical Systems, Palo Alto, California). The structures, together with the 4-dimensional computed tomography set, were exported into an in-house software, with which a 3-stage B-spline deformable registration was carried out to map the subregion and warp GTV contour to other breathing phases. The center of mass of the GTV was computed using the contours, and the tumor motion was appraised as the excursion of the center of mass between 0% phase and other phases. Application of the algorithm to the 10 patients showed that clinically satisfactory outcomes were achievable with a spatial accuracy around 2 mm for GTV contour propagation between adjacent phases and 3 mm between opposite phases. The tumor excursion was determined in the vast range of 1 mm through 1.6 cm, depending on the tumor location and tumor size. Compared to the traditional whole image-based registration, the regional method was found computationally a factor of 5 more efficient. The proposed technique has demonstrated its capability in extracting thoracic tumor motion and should find its application in 4-dimensional radiation therapy in the future to maximally utilize the available spatial-temporal information.

Tracking fuzzy borders using geodesic curves with application to liver segmentation on planning CT

PURPOSE

This work aims to develop a robust and efficient method to track the fuzzy borders between liver and the abutted organs where automatic liver segmentation usually suffers, and to investigate its applications in automatic liver segmentation on noncontrast-enhanced planning computed tomography (CT) images.

METHODS

In order to track the fuzzy liver-chestwall and liver-heart borders where oversegmentation is often found, a starting point and an ending point were first identified on the coronal view images; the fuzzy border was then determined as a geodesic curve constructed by minimizing the gradient-weighted path length between these two points near the fuzzy border. The minimization of path length was numerically solved by fast-marching method. The resultant fuzzy borders were incorporated into the authors' automatic segmentation scheme, in which the liver was initially estimated by a patient-specific adaptive thresholding and then refined by a geodesic active contour model. By using planning CT images of 15 liver patients treated with stereotactic body radiation therapy, the liver contours extracted by the proposed computerized scheme were compared with those manually delineated by a radiation oncologist.

RESULTS

The proposed automatic liver segmentation method yielded an average Dice similarity coefficient of 0.930 ± 0.015, whereas it was 0.912 ± 0.020 if the fuzzy border tracking was not used. The application of fuzzy border tracking was found to significantly improve the segmentation performance. The mean liver volume obtained by the proposed method was 1727 cm(3), whereas it was 1719 cm(3) for manual-outlined volumes. The computer-generated liver volumes achieved excellent agreement with manual-outlined volumes with correlation coefficient of 0.98.

CONCLUSIONS

The proposed method was shown to provide accurate segmentation for liver in the planning CT images where contrast agent is not applied. The authors' results also clearly demonstrated that the application of tracking the fuzzy borders could significantly reduce contour leakage during active contour evolution.

Commissioning a 50-100 kV X-ray unit for skin cancer treatment

This study provides the authors' experience along with dosimetric data from the commissioning of two Sensus SRT‐100 50‐100 kV X‐ray units. Data collected during the commissioning process included: a) HVL, b) output (dose rate), c) applicator cone factors, and d) percentage depth dose. A Farmer‐type chamber (PTW‐N23333), and a thin‐window parallel plate ion chamber (PTW‐N23342) were used for dose rate measurements and dose profiles were measured with EBT3 GafChromic film. The average HVL values for 50, 70, and 100 kV of the two treatment units were found to be 0.52, 1.15, and 2.20 mm Al, respectively. The HVL's were 5%–9% lower when measured with the Farmer chamber, as compared to measurements with the parallel plate chamber, for energies of 70 and 100 kV. Dose rates were also measured to be 3%–4% lower with the Farmer chamber. The dose rate variation between the two units was found to be 2%–9% for 50, 70, and 100 kV. The dose uniformity over a circle of 2 cm diameter was within 4% in four cardinal directions; however, the dose profiles for the 5 cm applicator were nonuniform, especially in the cathode–anode direction. Measurements indicated as much as 15% lower dose for the 50 kV beam at field edge on the anode side, when normalized to the center. The crossline profile was relatively more symmetric, with a maximum deviation of 10% at the field edge. All ion chamber readings agreed with film measurements within 3%. The nonuniform profile produced by these units may introduce uncertainty in dose rate measurements, especially for larger applicators. Since there is no intrinsic tool (crosshair or field light) for alignment with the beam axis, the user should take care when positioning the chamber for output measurements. The data obtained with a Farmer‐type chamber should be used cautiously and as a reference only for the SRT‐100 X‐ray treatment unit.

PACS number: 87.53.Bn

Adjoint acceleration of Monte Carlo simulations using TORT/MCNP coupling approach: a case study on the shielding improvement for the cyclotron room of the Buddhist Tzu Chi General Hospital

Full-scale Monte Carlo simulations of the cyclotron room of the Buddhist Tzu Chi General Hospital were carried out to improve the original inadequate maze design. Variance reduction techniques are indispensable in this study to facilitate the simulations for testing a variety of configurations of shielding modification. The TORT/MCNP manual coupling approach based on the Consistent Adjoint Driven Importance Sampling (CADIS) methodology has been used throughout this study. The CADIS utilises the source and transport biasing in a consistent manner. With this method, the computational efficiency was increased significantly by more than two orders of magnitude and the statistical convergence was also improved compared to the unbiased Monte Carlo run. This paper describes the shielding problem encountered, the procedure for coupling the TORT and MCNP codes to accelerate the calculations and the calculation results for the original and improved shielding designs. In order to verify the calculation results and seek additional accelerations, sensitivity studies on the space-dependent and energy-dependent parameters were also conducted.

The refined shielding design for the cyclotron room of the Buddhist Tzu Chi General Hospital

Full-scale Monte Carlo simulations of the cyclotron room of the Buddhist Tzu Chi General Hospital were carried out to improve the inadequate maze design. The double differential neutron source from the 18O(p,n)18F reaction was adopted for the calculation. The weight window variance reduction technique, where the weight window was set by applying the adjoint flux, has been implemented in the MCNP run to facilitate the calculation of the dose rates outside the cyclotron room. Dose rates including neutron and gamma-ray components were calculated for some maze shielding modifications.

Evaluation of the dose rate distribution for an air-type 60Co irradiation facility

The dose rate distributions in the 29,000-Ci 60Co irradiation facility in National Tsing Hua University were investigated by measurements and calculations. The dose rate measurements were performed using radiochromic dye films and an Exradin A2 ion chamber mounted on a PC-controlled motorised vertical translation stage. The calculations were made by using the three-dimensional point kernel code QAD-CGGP with detailed source composition and geometry modelling. The scattered gamma rays from the walls of the irradiation cell were also evaluated by using the Monte Carlo code MCNP.