Stereotactic Body Radiation Therapy for Gynecologic Malignancies: A Case-Based Radiosurgery Society Practice Review

PURPOSE

The use of stereotactic body radiation therapy (SBRT) for gynecologic malignancies is controversial. We discuss certain circumstances when highly precise SBRT may be a useful tool to consider in the management of selected patients.

METHODS AND MATERIALS

Case selection included the following scenarios, the first 2 with palliative intent, para-aortic nodal oligorecurrence of ovarian cancer, pelvic sidewall oligorecurrence of cervical cancer, and inoperable endometrial cancer boost after intensity modulated radiation to the pelvis treated with curative intent. Patient characteristics, fractionation, prescription dose, treatment technique, and dose constraints were discussed. Relevant literature to these cases was summarized to provide a framework for treatment of similar patients.

RESULTS

Treatment of gynecologic malignancies with SBRT requires many considerations, including treatment intent, optimal patient selection, fractionation selection, tumor localization, and plan optimization. Although other treatment paradigms including conventionally fractionated radiation therapy and brachytherapy remain the standard-of-care for definitive treatment of gynecologic malignancies, SBRT may have a role in palliative cases or those where high doses are not required due to the unacceptable toxicity that may occur with SBRT.

CONCLUSIONS

A case-based practice review was developed by the Radiosurgery Society to provide a practical guide to the common scenarios noted above affecting patients with gynecologic malignancies.

Updated Trends in Cervical Cancer Brachytherapy Utilization and Disparities in the United States From 2004 to 2020

PURPOSE

Lower brachytherapy utilization for cervical cancer patients is associated with decreased survival. This study examines more recent trends in brachytherapy utilization from 2004 to 2020 to assess any trend reversal after awareness increased regarding the importance of brachytherapy.

METHODS AND MATERIALS

This study analyzed data from the National Cancer Database of patients with Federation of Gynecology and Obstetrics (FIGO) IB to IVA cervical cancer treated with radiation therapy between 2004 and 2020. To compare brachytherapy utilization over time, 2- to 3-year categories were created to account for potential variation seen in individual years. A multivariate log binomial regression with robust variance was used to estimate the incidence rate ratio (IRR) of brachytherapy utilization in each year category in reference to the 2004-2006 category. Additionally, risk factors for brachytherapy utilization were identified.

RESULTS

Overall brachytherapy utilization for cervical cancer increased from 54.9% in 2004 to 75.7% in 2020. Compared with 2004 to 2006 when rates of utilization totaled 55.2%, brachytherapy utilization significantly increased to 63.4% in 2011 to 2014 (IRR, 1.15; 95% CI, 1.11-1.19), 66.0% in 2015 to 2017 (1.20 [1.16-1.23]), and 76.0% in 2018 to 2020 (1.38 [1.34-1.42]). Sociodemographic factors associated with lower brachytherapy utilization included Black race (0.94 [0.92-0.97]), Hispanic ethnicity (0.92 [0.90-0.95]), and age >59 years (age ≥60-69: 0.96 [0.94-0.98]; age ≥70-79: 0.89 [0.87-0.92]; age ≥80: 0.73 [0.69-0.77]). Positive predictors of brachytherapy utilization included having insurance (IRR, 1.11; 95% CI, 1.07-1.14).

CONCLUSIONS

In patients with FIGO IB-IVA cervical cancer treated with radiation therapy from 2004 to 2020, brachytherapy utilization has increased during the past decade. These results are encouraging given the known benefit to cause-specific survival and overall survival provided by brachytherapy treatment and indicate a reversal in the trend of declining brachytherapy noted previously. Concerns related to disparities by race, ethnicity, and insurance status require further interventions.

Updated Trends in the Utilization of Brachytherapy in Cervical Cancer in the United States: A Surveillance, Epidemiology, and End-Results Study

PURPOSE

Our previous Surveillance, Epidemiology, and End Results (SEER) study revealed a concerning decline in brachytherapy utilization in the United States between 1988 and 2009. This study evaluates recent trends in brachytherapy utilization in cervical cancer and identifies factors and survival benefit associated with the use of brachytherapy treatment.

METHODS AND MATERIALS

Using SEER data, 8500 patients with International Federation of Gynecologists and Obstetricians 2009 stage IB2-IVA cervical cancer treated with external beam radiation therapy (EBRT) between 2000 and 2020 were identified. Logistic regression analysis was performed on potential factors associated with brachytherapy use: age, marital status, race, ethnicity, income, metropolitan status, year of diagnosis, SEER region, histology, grade, and stage. To adjust for differences between patients who received brachytherapy and those who did not, propensity-score matching was used. Multivariable Cox regression analysis assessed the association of brachytherapy use with cervical cancer-specific mortality (CSM) and all-cause mortality (ACM) in the matched cohort.

RESULTS

Sixty-four percent of the 8500 women received brachytherapy in combination with EBRT; 36% received EBRT alone. The brachytherapy utilization rate declined sharply in 2003/2004 (lowest rate 44% in 2003) and then gradually improved especially in 2018 to 2020 (76%). Factors associated with higher odds of brachytherapy use included younger age, married (vs single), later years of diagnosis, certain SEER regions, and earlier stage. In the propensity-score matched cohort, brachytherapy treatment was associated with lower 4-year cumulative incidence of cancer death (32.1% vs 43.4%; P < .001) and better overall survival (64.0% vs 51.4%; P < .001). Brachytherapy treatment was independently associated with lower CSM (hazard ratio, 0.70; 95% CI, 0.64-0.76; P < .001) and ACM (hazard ratio, 0.72; 95% CI, 0.67-0.78; P < .001).

CONCLUSIONS

Brachytherapy utilization among SEER regions has improved since 2004 in patients with stage IB2-IVA cervical cancer. Brachytherapy use remains independently associated with significantly lower CSM and ACM and is an essential component of treatment for patients with locally advanced cervical cancer.

Risk Factors and Survival Impact Associated With Documentation of Radiation Therapy Refusal in Patients With Gynecologic Cancer

PURPOSE

Radiation therapy (RT) refusal is known to have deleterious effects on survival for multiple cancer types. Factors associated with RT refusal by patients with gynecologic malignancies have not been well described. This study aimed to examine factors associated with and the survival impact of documented RT refusal among patients with gynecologic cancers.

METHODS AND MATERIALS

This study analyzed data from the National Cancer Database (NCDB) of patients with gynecologic cancers diagnosed between 2004 and 2020. Patients were included if they had complete survival data and a documented RT recommendation by their treating physician in the NCDB. Patients coded as received RT were compared with those coded as refused RT in the NCDB using a multivariate log binomial regression with robust variance to yield incidence rate ratios (IRR). Overall survival was analyzed using a multivariate (MV) Cox proportional hazards model to yield hazard ratios.

RESULTS

This study identified 209,976 patients. A total of 5.75% (n = 12,081) patients were coded as refusing RT. Multivariable IRR showed that documentation of RT refusal was positively associated with older age (MV IRR, 1.04; 95% CI, 1.041-1.045), Native Hawaiian Pacific Islander race (1.72 [1.27-2.32]), and increased morbidity (score = 1: 1.06 [1.02-1.11]; score = 2: 1.20 [1.12-1.29]; score ≥3: 1.26 [1.14-1.38]). Negative associations were seen with Hispanic ethnicity (0.74 [0.67-0.80]), having insurance (0.58 [0.53-0.63]), and annual income >$74,063 (0.85 [0.81-0.90]). During the 16-year period, a statistically significant test for trend (P = .001) for increasing RT refusal was noted. RT refusal was associated with a significantly higher risk of death (MV hazard ratio, 1.59 [1.55-1.63]).

CONCLUSIONS

For patients with gynecologic malignancies diagnosed from 2004 to 2020, an increase in documented RT refusal is associated with decreased overall survival in all disease types. Targeted interventions aimed at mitigating potential sociodemographic barriers to receipt of RT are warranted.

FLASH Effects Induced by Orthovoltage X-Rays

PURPOSE

This work describes the first implementation and in vivo study of ultrahigh-dose-rate radiation (>37 Gy/s; FLASH) effects induced by kilovoltage (kV) x-ray from a rotating-anode x-ray source.

METHODS AND MATERIALS

A high-capacity rotating-anode x-ray tube with an 80-kW generator was implemented for preclinical FLASH radiation research. A custom 3-dimensionally printed immobilization and positioning tool was developed for reproducible irradiation of a mouse hind limb. Calibrated Gafchromic (EBT3) film and thermoluminescent dosimeters (LiF:Mg,Ti) were used for in-phantom and in vivo dosimetry. Healthy FVB/N and FVBN/C57BL/6 outbred mice were irradiated on 1 hind leg to doses up to 43 Gy at FLASH (87 Gy/s) and conventional (CONV; <0.05 Gy/s) dose rates. The radiation doses were delivered using a single pulse with the widths up to 500 ms and 15 minutes at FLASH and CONV dose rates. Histologic assessment of radiation-induced skin damage was performed at 8 weeks posttreatment. Tumor growth suppression was assessed using a B16F10 flank tumor model in C57BL6J mice irradiated to 35 Gy at both FLASH and CONV dose rates.

RESULTS

FLASH-irradiated mice experienced milder radiation-induced skin injuries than CONV-irradiated mice, visible by 4 weeks posttreatment. At 8 weeks posttreatment, normal tissue injury was significantly reduced in FLASH-irradiated animals compared with CONV-irradiated animals for histologic endpoints including inflammation, ulceration, hyperplasia, and fibrosis. No difference in tumor growth response was observed between FLASH and CONV irradiations at 35 Gy. The normal tissue sparing effects of FLASH irradiations were observed only for high-severity endpoint of ulceration at 43 Gy, which suggests the dependency of biologic endpoints to FLASH radiation dose.

CONCLUSIONS

Rotating-anode x-ray sources can achieve FLASH dose rates in a single pulse with dosimetric properties suitable for small-animal experiments. We observed FLASH normal tissue sparing of radiation toxicities in mouse skin irradiated at 35 Gy with no sacrifice to tumor growth suppression. This study highlights an accessible new modality for laboratory study of the FLASH effect.

Defining the Transcriptional Landscapes of the Tumor Microenvironment of Cervical and Vaginal Cancers at Single-Cell Resolution

PURPOSE/OBJECTIVE(S)

Malignancies found within vaginal tissue are often diagnosed as cancers of the cervix, vulva, or urethra and are clinically treated with similar modalities. However, the rarity of vaginal cancer may be an artifice of categorization; current treatment paradigms do not take into account tissue-specific mutations and differences in mechanistic pathways intracellularly. Understanding the shared and distinctly different transcriptional profiles of vaginal and cervical tumors at a single-cell resolution will provide insights in vaginal tumor biology and will open avenues for future clinical interventions.

MATERIALS/METHODS

Biopsies of tumor and adjacent normal tissue from 9 patients (3 adenocarcinomas (ADC), 3 squamous cell carcinomas (SCC) from the cervix, and 3 vaginal SCC) were collected and analyzed by single-cell RNA sequencing (scRNA-seq) to compare the tumor, immune, and stromal features of cervical and vaginal cancers.

RESULTS

Collectively, over 50,000 cells were analyzed by scRNA-seq in this study. We performed dimensionality reduction and clustering analysis of the single-cell transcriptomes to identify the major cell types composing the vaginal and cervical tumor tissues. Compared to Cervical SCC, Vaginal SCC tissues showed reduced fractions of macrophages (-2.7 log2-fold; padj < 0.02) and T cells (-3.7 log2-fold; padj < 0.02) by differential cell proportion analysis (RAISIN). Likewise, the vaginal SCC epithelial cell compartments showed downregulation of inflammatory pathways including TNF signaling via NFKB (NES = -5.7, padj = 5.0 × 10-19), IL2 STAT5 signaling (NES = -4.5, padj = 1.6 × 10-12), and interferon gamma response (NES = -4.3, padj = 9.4 × 10-12), among the Hallmark pathway collection. On the other hand, vaginal SCC epithelial cells showed significant upregulation of oxidative phosphorylation (NES = 4.8, padj = 1.7 × 10-17), p53 pathway (NES = 4.2, padj = 1.8 × 10-13), mTORC1 signaling (NES = 4.2, padj = 1.9 × 10-13), and estrogen early and late response (NES = 4.0, padj < 7.5 × 10-12) compared to cervical SCC.

CONCLUSION

These results highlight distinct differences in the cell type composition and cancer epithelial pathways in vaginal vs. cervical SCC. Among upregulated pathways in vaginal SCC, ER and mTORC1 pathway activation may represent targets for therapeutic intervention worthy of further investigation.

Combined trastuzumab and radiation therapy for HER2-positive uterine serous carcinoma: A case report

Overexpression of HER2 in endometrial cancer is associated with poor prognosis, aggressive disease, and resistance to standard therapies. Recent studies have shown that HER2-targeted therapies, such as trastuzumab, can be effective in treating HER2-positive endometrial cancer in combination with chemotherapy. Currently, the management of advanced-stage HER2-positive uterine serous carcinoma (USC) consists of adjuvant platinum-based chemotherapy with concurrent trastuzumab followed by trastuzumab maintenance therapy until disease recurrence or prohibitive toxicity. In the setting of persistent pelvic disease following systemic therapy, consolidation with tumor-directed radiation therapy also offers an opportunity to eradicate residual disease. With the emergence of molecular tumor classifications and systemic therapies (chemotherapy, immunotherapy, and target therapies), the landscape of adjuvant multi-modality therapy is ever changing and increasingly individualized. Currently, there is no prospective evidence to guide pelvic radiotherapy with concurrent trastuzumab in endometrial cancer, and as a result, no reported toxicity in endometrial cancer patients. In this case report, we present two patients with HER2-positive USC who received multi-agent chemotherapy with trastuzumab followed by pelvic radiation therapy and concurrent trastuzumab. Both patients tolerated this multimodal treatment without significant or persistent moderate or severe adverse events. These two cases provide insight into the safety and feasibility of administering radiation therapy with trastuzumab in endometrial cancer in the maintenance phase. Our report suggests that trastuzumab-based therapy may be a promising treatment option for HER2-positive endometrial cancer patients who receive concurrent or adjuvant chemotherapy and radiation therapy.

Image Derived Estimates of Fibrosis Using Ultrashort Echo Time MRI in Gynecologic Cancer

PURPOSE/OBJECTIVE(S)

Fibrosis forms during and after radiation therapy (RT) due to wound-healing and cell death. In gynecologic cancer patients treated with EBRT and HDR, we evaluated image derived (ID) acute fibrosis (IDFA) and chronic fibrosis (IDFC) estimates using non-contrast and late gadolinium contrast enhanced (LGE) inversion recovery ultrashort echo time (IR UTE) MRI, respectively. We hypothesized that that ID markers can quantify FA and FC within tumor as a result of response to RT and that fibrosis changes over the course of RT are associated with tumor regression.

MATERIALS/METHODS

Subjects: Three subjects with cervical squamous cell carcinoma (SCC), 1 subject with cervical adenocarcinoma, and 2 subjects with vaginal SCC undergoing RT were included. Image Acquisition & Analysis: 1.5T MR imaging at four time-points (TPs): pre-RT, on-RT, post-RT, and post 3mo RT. IDFA imaging: Stack of spirals dual echo (TE = 50, 2690µs), TI = 60ms IR UTE research application. Subtracting the two echoes yielded short TE signal intensity (SI). IDFC imaging: stack of spirals dual echo IR UTE research application, TE = 50µs, TI = 200ms, acquired 15 minutes following contrast. Remnant tumor was contoured at each TP with T2, ADC, and DCE. Relative IDFA, IDFC quantification: voxel-wise IR UTE and LGE IR UTE signal intensity (SI) normalized to gluteal muscle SI. The sum of normalized IDFA and IDFC SI within the remnant tumor at each TP was divided by the corresponding tumor volume yielding tumor intensity (TI) TIFA and TIFC fibrosis accumulation estimates.

STATISTICS

The coefficients of variation (COV) for TIFA and TIFC were calculated by varying tumor margins and re-computing TIFA and TIFC. Univariate relationships were evaluated using linear regression.

RESULTS

The COVs for TIFA = 13% and TIFC = 7%. IDFA and IDFC were observed pre-RT on the tumor periphery, on-RT and post-RT within the tumor, with IDFA potentially transforming into IDFC. Table 1 shows that a greater decrease in tumor volume post RT was correlated with a larger pre-RT TIFA (r = -0.85, p = .03). Decrease in tumor volume was correlated with a larger TIFC post-RT (r = -0.79, p = .05). Post 3 month TIFC was associated with tumor reduction (r = 0.82, n = 4).

CONCLUSION

In this pilot study, we developed reproducible methods to quantify IDFA and IDFC within remnant tumor. Our results suggest that IDFA and IDFC may be associated with tumor response based on tumor volume.

Quantifying Value in an Iterative Disease-Site Specific Peer Review System

PURPOSE/OBJECTIVE(S)

To assess the greatest impact of peer review on treatment planning and plan modification in two disease-site specific peer review groups to improve quality assurance workflow.

MATERIALS/METHODS

We implemented an iterative peer review checklist tool and treatment planning registry to document recommendations and time spent in breast and thoracic disease-site specific peer review. Plan review included discussion of the clinical scenario, radiation dose/fractionation, prescription, organs at risk and target volumes, planning metrics including dose volume histogram and patient setup. Pre-treatment (Pre-tx) review of volumes and plans occurred prior to treatment start for definitive plans of ≤five fractions or using protons, and cases were re-reviewed in subsequent sessions to complete checklist items as needed. Reviews were graded as follows: discussion (no required changes), minor recommendations (changes recommended at attending discretion) and major recommendations (changes required). Students t-test and chi-squared analysis were used to identify statistical significance.

RESULTS

We identified 723 peer reviews over a 3-month period: 275 thoracic reviews of 195 unique patients (32% reviewed ≥twice), and 448 breast reviews of 273 unique patients (48% reviewed ≥twice, most commonly for a boost plan). On average, pre-tx review doubled the amount of time spent per case, (4:47min versus 2:03min, p<0.01) and resulted in significantly more discussion (29.3% vs 9.3%, p<0.01), minor changes recommended (13.2% versus 4.8%, p<0.01) and plan revision (19.2% versus 2.4%, p<0.01). Thoracic pre-tx reviews were twice as long as breast (5:43min versus 3:00min, p<0.01), and had a greater proportion of cases prompting discussion (26.7% vs 13.2%, p<0.01) and minor changes recommended (12.8% vs 6.3%, p<0.01). No time difference was found in regular review (2:19min vs 1:58 min, p = 0.09). The most frequent discussion/recommendation topics also varied by group with planning metrics in thoracic cases (14.9%) and setup imaging including PORT films and electron setup (5.1%) in breast (Table).

CONCLUSION

Iterative plan review with pre-review for selected cases encouraged educational discussion and plan revision, with notable variability by disease site. Thoracic cases required longer review time and had more frequent plan change recommendations likely reflecting differences in case complexity. In contrast, setup imaging in breast cases, which are more commonly 3D or electron-based, more frequently warranted discussion/revision and should be considered within the peer review paradigm.

Selective de-implementation of routine in vivo dosimetry

As cone-beam computed tomography (CBCT) has become the localization method for a majority of cases, the indications for diode-based confirmation of accurate patient set-up and treatment are now limited and must be balanced between proper resource allocation and optimizing efficiency without compromising safety. We undertook a de-implementation quality improvement project to discontinue routine diode use in non-intensity modulated radiotherapy (IMRT) cases in favor of tailored selection of scenarios where diodes may be useful. After analysis of safety reports from the last 5 years, literature review, and stakeholder discussions, our safety and quality (SAQ) committee introduced a recommendation to limit diode use to specific scenarios in which in vivo verification may add value to standard quality assurance (QA) processes. To assess changes in patterns of use, we reviewed diode use by clinical indication 4 months prior and after the implementation of the revised policy, which includes use of diodes for: 3D conformal photon fields set up without CBCT; total body irradiation (TBI); electron beams; cardiac devices within 10 cm of the treatment field; and unique scenarios on a case-by-case basis. We identified 4459 prescriptions and 1038 unique instances of diode use across five clinical sites from 5/2021 to 1/2022. After implementation of the revised policy, we observed an overall decrease in diode use from 32% to 13.2%, with a precipitous drop in 3D cases utilizing CBCT (from 23.2% to 4%), while maintaining diode utilization in the 5 selected scenarios including 100% of TBI and electron cases. By identifying specific indications for diode use and creating a user-friendly platform for case selection, we have successfully de-implemented routine diode use in favor of a selective process that identifies cases where the diode is important for patient safety. In doing so, we have streamlined patient care and decreased cost without compromising patient safety.

From Alpha to Omicron: A Radiation Oncology Network's Biocontainment-Based COVID-19 Experience

Purpose

To develop the safest possible environment for treating urgent patients with COVID-19 requiring radiation, we describe the unique construction of negative air pressure computed tomography simulator and linear accelerator treatment vaults in addition to screening, delay, and treatment protocols and their evolution over the course of the COVID-19 pandemic.

Methods and Materials

Construction of large high-efficiency particulate air filter air-flow systems into existing ductwork in computed tomography simulator rooms and photon and proton treatment vaults was completed to create negative-pressure rooms. An asymptomatic COVID-19 screening protocol was implemented for all patients before initiation of treatment. Patients could undergo simulation and/or treatment in the biocontainment environments according to a predefined priority scale and protocol. Patients treated under the COVID-19 protocol from June 2020 to January 2022 were retrospectively reviewed.

Results

Negative air-flow environments were created across a regional network, including a multi-gantry proton therapy unit. In total, 6525 patients were treated from June 2020 through January 2022 across 5 separate centers. The majority of patients with COVID-19 had radiation treatment deferred when deemed safe. A total of 42 patients with COVID-19, who were at highest risk of an adverse outcome should there be a radiation delay, were treated under the COVID-19 biocontainment protocol in contrast to those who were placed on treatment break. For 61.9% of patients, these safety measures mitigated an extended break during treatment. The majority of patients (64.3%) were treated with curative intent. The median number of biocontainment sessions required by each patient was 6 (range, 1-15) before COVID-19 clearance and resumption of treatment in a normal air-flow environment.

Conclusions

Constructing negative-pressure environments and developing a COVID-19 biocontainment treatment protocol allowed for the safe treatment of urgent radiation oncology patients with COVID-19 within our department and strengthens future biopreparedness. These biocontainment units set a high standard of safety in radiation oncology during the current or for any future infectious outbreak.

3D-printed Magnetic Resonance (MR)-based gynecological phantom for image-guided brachytherapy training

PURPOSE/OBJECTIVES

There is a clinical need to develop anatomic phantoms for simulation-based learning in gynecological brachytherapy. Here, we provide a step-by-step approach to build a life-sized gynecological training phantom based on magnetic resonance imaging (MRI) of an individual patient. Our hypothesis is that this phantom can generate convincing ultrasound (US) images that are similar to patient scans.

METHODS

Organs-at-risk were manually segmented using patient scans (MRI). The gynecological phantom was constructed using positive molds from 3D printing and polyvinyl chloride (PVC) plastisol. Tissue texture/acoustic properties were simulated using different plastic softener/hardener ratios and microbead densities. Nine readers (residents) were asked to evaluate 10 cases (1 ultrasound image per case) and categorize each as a "patient" or "phantom" image. To evaluate whether the phantom and patient images were equivalent, we used a multireader, multicase equivalence study design with two composite null hypotheses with proportion (pr) at H01: pr ≤ 0.35 and H02: pr ≥ 0.65. Readers were also asked to review US videos and identify the insertion of an interstitial needle into the pelvic phantom. Computed Tomography (CT) and magnetic resonance (MR) images of the phantom were acquired for a feasibility study.

RESULTS

Readers correctly classified "patient" and "phantom" scans at pr = 53.3% ± 6.2% (p values 0.013 for H01 and 0.054 for H02, df = 5.96). Readers reviewed US videos and identified the interstitial needle 100% of the time in transabdominal view, and 78% in transrectal view. The phantom was CT and MR safe.

CONCLUSIONS

We have outlined a manufacturing process to create a life-sized, gynecological phantom that is compatible with multi-modality imaging and can be used to simulate clinical scenarios in image-guided brachytherapy procedures.

Improving Quality Metrics in Radiation Oncology: Implementation of Pretreatment Peer Review for Stereotactic Body Radiation Therapy in Patients with Thoracic Cancer

Purpose

Traditional peer reviews occur weekly, and can take place up to 1 week after the start of treatment. The American Society for Radiation Oncology peer-review white paper identified stereotactic body radiation therapy (SBRT) as a high priority for contour/plan review before the start of treatment, considering both the rapid-dose falloff and short treatment course. Yet, peer-review goals for SBRT must also balance physician time demands and the desire to avoid routine treatment delays that would occur in the setting of a 100% pretreatment (pre-Tx) review compliance requirement or prolonging the standard treatment planning timeline. Herein, we report on our pilot experience of a pre-Tx peer review of thoracic SBRT cases.

Methods and Materials

From March 2020 to August 2021, patients undergoing thoracic SBRT were identified for pre-Tx review, and placed on a quality checklist. We implemented twice-weekly meetings for detailed pre-Tx review of organ-at-risk/target contours and dose constraints in the treatment planning system for SBRT cases. Our quality metric goal was to peer review ≥90% of SBRT cases before exceeding 25% of the dose delivered. We used a statistical process control chart with sigma limits (ie, standard deviations [SDs]) to access compliance rates with pre-Tx review implementation.

Results

We identified 252 patients treated with SBRT to 294 lung nodules. When comparing pre-Tx review completion from initial rollout to full implementation, our rates improved from 19% to 79% (ie, from 1 sigma limit [SDs]) below to >2 sigma limits (SDs) above. Additionally, early completion of any form of contour/plan review (defined as any pre-Tx or standard review completed before exceeding 25% of the dose delivered) increased from 67% to 85% (March 2020-November 2020) to 76% to 94% (December 2020-August 2021).

Conclusions

We successfully implemented a sustainable workflow for detailed pre-Tx contour/plan review for thoracic SBRT cases in the context of twice-weekly disease site-specific peer-review meetings. We reached our quality improvement objective to peer review ≥90% of SBRT cases before exceeding 25% of the dose delivered. This process was feasible to conduct in an integrated network of sites across our system.

Fully automated segmentation of clinical target volume in cervical cancer from magnetic resonance imaging with convolutional neural network

PURPOSE

Contouring clinical target volume (CTV) from medical images is an essential step for radiotherapy (RT) planning. Magnetic resonance imaging (MRI) is used as a standard imaging modality for CTV segmentation in cervical cancer due to its superior soft-tissue contrast. However, the delineation of CTV is challenging as CTV contains microscopic extensions that are not clearly visible even in MR images, resulting in significant contour variability among radiation oncologists depending on their knowledge and experience. In this study, we propose a fully automated deep learning-based method to segment CTV from MR images.

METHODS

Our method begins with the bladder segmentation, from which the CTV position is estimated in the axial view. The superior-inferior CTV span is then detected using an Attention U-Net. A CTV-specific region of interest (ROI) is determined, and three-dimensional (3-D) blocks are extracted from the ROI volume. Finally, a CTV segmentation map is computed using a 3-D U-Net from the extracted 3-D blocks.

RESULTS

We developed and evaluated our method using 213 MRI scans obtained from 125 patients (183 for training, 30 for test). Our method achieved (mean ± SD) Dice similarity coefficient of 0.85 ± 0.03 and the 95th percentile Hausdorff distance of 3.70 ± 0.35 mm on test cases, outperforming other state-of-the-art methods significantly (p-value < 0.05). Our method also produces an uncertainty map along with the CTV segmentation by employing the Monte Carlo dropout technique to draw physician's attention to the regions with high uncertainty, where careful review and manual correction may be needed.

CONCLUSIONS

Experimental results show that the developed method is accurate, fast, and reproducible for contouring CTV from MRI, demonstrating its potential to assist radiation oncologists in alleviating the burden of tedious contouring for RT planning in cervical cancer.

ACR-ABS-ASTRO Practice Parameter for the Performance of Low-Dose-Rate Brachytherapy

AIM/OBJECTIVES/BACKGROUND

The American College of Radiology (ACR), the American Brachytherapy Society (ABS), and the American Society for Radiation Oncology (ASTRO) have jointly developed the following practice parameter for the performance of low-dose-rate (LDR) brachytherapy. LDR brachytherapy is the application of radioactive sources in or on tumors in a clinical setting with therapeutic intent. The advantages of LDR brachytherapy include improving therapeutic ratios with lower doses to nontarget organs-at-risk and higher doses to a specific target.

METHODS

This practice parameter was developed according to the process described under the heading. The Process for Developing ACR Practice Parameters and Technical Standards on the ACR website (https://www.acr.org/Clinical-Resources/Practice-Parameters-and-Technical-Standards) by the Committee on Practice Parameters-Radiation Oncology of the Commission on Radiation Oncology, in collaboration with ABS and ASTRO.

RESULTS

This practice parameter was developed to serve as a tool in the appropriate application of this evolving technology in the care of cancer patients or other patients with conditions where radiation therapy is indicated. It addresses clinical implementation of LDR brachytherapy including personnel qualifications, quality assurance standards, indications, and suggested documentation. This includes a contemporary literature search.

CONCLUSIONS

This practice parameter is a tool to guide the use of LDR brachytherapy and does not assess relative clinical indication for LDR brachytherapy when compared with other forms of brachytherapy or external beam therapy, but to focus on the best practices required to deliver LDR brachytherapy safely and effectively, when clinically indicated. Comparative costs of versus other modalities therapy may also need to be considered.

Radiation oncology management of stage III and IVA cervical carcinoma

Worldwide, stage III-IVA carcinomas of the uterine cervix comprise a significant proportion of cases at presentation, and have a higher rate of recurrence and worse overall survival. This review will discuss the epidemiology, prevention strategies, clinical presentation, and treatment recommendations for stage III-IVA cervical cancer. The focus will be on the role of radiation therapy, concurrent chemoradiotherapy, and brachytherapy, including the potential benefits and anticipated toxicities. The unique challenges and considerations of fistula formation and approaches to management will be highlighted, and follow-up care and future directions discussed. As low and middle income countries bear the highest burden of advanced stage carcinoma of the uterine cervix, this review will address the unique needs of global communities.

MR-Tracked Deflectable Stylet for Gynecologic Brachytherapy

Brachytherapy is a radiation based treatment that is implemented by precisely placing focused radiation sources into tumors. In advanced interstitial cervical cancer bracytherapy treatment, this is performed by placing a metallic rod ("stylet") inside a hollow cylindrical tube ("catheter") and advancing the pair to the desired target. The stylet is removed once the target is reached, followed by the insertion of radiation sources into the catheter. However, manually advancing an initially straight stylet into the tumor with millimeter spatial accuracy has been a long-standing challenge, which requires multiple insertions and retractions, due to the unforeseen stylet deflection caused by the stiff muscle tissue that is traversed. In this paper, we develop a novel tendon-actuated deflectable stylet equipped with MR active-tracking coils that may enhance brachytherapy treatment outcomes by allowing accurate stylet trajectory control. Herein we present the design concept and fabrication method, followed by the kinematic and mechanics models of the deflectable stylet. The hardware and theoretical models are extensively validated via benchtop and MRI-guided characterization. At insertion depths of 60 mm, benchtop phantom targeting tests provided a targeting error of 1. 23 ± 0. 47 mm, and porcine tissue targeting tests provided a targeting error of 1. 65 ± 0. 64 mm, after only a single insertion. MR-guided experiments indicate that the stylet can be safely and accurately located within the MRI environment.

Increasing global accessibility to high-level treatments for cervical cancers

Human papillomaviruses (HPV)-related gynecological cancers are a major health care issue, and a leading cause of cancer death in low- and middle-income countries (LMIC). In 2020, the World Health Organization launched a program aimed at cervical cancer elimination, by screening and vaccination strategies. Offering the best possible care to women diagnosed with invasive cancer is a complementary objective. Treatment of cervical cancer as per modern standards is complex and multimodal, mainly relying on surgery, external-beam radiotherapy (+/-chemotherapy) and brachytherapy. In parallel with the pivotal role of multidisciplinary discussion, international societies provide guidance to define the most effective and least toxic anti-cancer strategy, homogenize treatment protocols and provide benchmark quality indicators as a basis for accreditation processes. The challenge is to offer the appropriate diagnostic workup and treatment upfront and to avoid non- evidence-based treatment that consumes resources, impairs quality of life (QoL), and compromises oncological outcome. Various strategies may be applied for improving treatment quality: development of surgical mentorship, companion-training programs and international cooperation. The lack of radiotherapy/brachytherapy facilities is a major concern in LMIC. Reinforcing international support in terms of education, training, research and development and technical cooperation with national projects is required to increase access to minimum requirements but also introduce modern techniques, upgrade radiotherapy/brachytherapy services, and expand access to modern systemic treatments. In countries with robust economies, compliance to standards should also be increased. Integrative cancer care and multidisciplinary approaches are needed to tackle the dual challenge of increasing cure rates while minimizing QoL impairment. Appropriate dimensioning of the resources to avoid harmful treatment delays and access to expert referral centers is also a priority.

An endovaginal MRI array with a forward-looking coil for advanced gynecological cancer brachytherapy procedures: Design and initial results

PURPOSE

To develop an endovaginal MRI array that provides signal enhancement forward into the posterior parametrium and sideways into the vaginal wall, accelerating multiple-contrast detection of residual tumors that survive external beam radiation. The array's enclosure should form an obturator for cervical cancer brachytherapy, allowing integration with MRI-guided catheter placement, CT, and interstitial radiation dose delivery.

METHODS

The endovaginal array consisted of forward-looking and sideways-looking components. The forward-looking element imaged the cervix and posterior endometrium, and the sideways-looking elements imaged the vaginal wall. Electromagnetic simulation was performed to optimize the geometry of a forward-looking coil placed on a conductive-metallic substrate, extending the forward penetration above the coil's tip. Thereafter, an endovaginal array with one forward-looking coil and four sideways-looking elements was constructed and tested at 1.5 Tesla in saline and gel phantoms, and three sexually mature swine. Each coil's tuning, matching, and decoupling were optimized theoretically, implemented with electronic circuits, and validated with network-analyzer measurements. The array enclosure emulates a conventional brachytherapy obturator, allowing use of the internal imaging array together with tandem coils and interstitial catheters, as well as use of the enclosure alone during CT and radiation delivery. To evaluate the receive magnetic field ( B 1 - ) spatial profile, the endovaginal array's specific absorption-rate (SAR) distribution was simulated inside a gel ASTM phantom to determine extreme heating locations in advance of a heating test. Heating tests were then performed during high SAR imaging in a gel phantom at the predetermined locations, testing compliance with MRI safety standards. To assess array imaging performance, signal-to-noise-ratios (SNR) were calculated in a saline phantom and in vivo. Swine images were acquired with the endovaginal array combined with the scanner's body and spine arrays.

RESULTS

Simulated B 1 - profiles for the forward-looking lobe pattern, obtained while varying several geometric parameters, disclosed that a forward-looking coil placed on a metal-backed substrate could double the effective forward penetration from approximately 25 to ∼40 mm. An endovaginal array, enclosed in an obturator enclosure was then constructed, with all coils tuned, matched, and decoupled. The ASTM gel-phantom SAR test showed that peak local SAR was 1.2 W/kg in the forward-looking coil and 0.3 W/kg in the sideways-looking elements, well within ASTM/FDA/IEC guidelines. A 15-min 4 W/kg average SAR imaging experiment resulted in less than 2^o C temperature increase, also within ASTM/FDA/IEC heating limits. In a saline phantom, the forward-looking coil and sideways-looking array's SNR was four to eight times, over a 20-30 mm field-of-view (FOV), and five to eight times, over a 15-25 mm FOV, relative to the spine array's SNR, respectively. In three sexually mature swine, the forward-looking coil provided a 5 + 0.2 SNR enhancement factor within the cervix and posterior endometrium, and the sideways-looking array provided a 4 + 0.2 SNR gain factor in the vaginal wall, relative to the Siemens spine array, demonstrating that the array could significantly reduce imaging time.

CONCLUSIONS

Higher SNR gynecological imaging is supported by forward-looking and sideways-looking coils. A forward-looking endovaginal coil for cervix and parametrium imaging was built with optimized metal backing. Array placement within an obturator enhanced integration with the brachytherapy procedure and accelerated imaging for detecting postexternal-beam residual tumors.

Fully automated multiorgan segmentation of female pelvic magnetic resonance images with coarse-to-fine convolutional neural network

PURPOSE

Brachytherapy combined with external beam radiotherapy (EBRT) is the standard treatment for cervical cancer and has been shown to improve overall survival rates compared to EBRT only. Magnetic resonance (MR) imaging is used for radiotherapy (RT) planning and image guidance due to its excellent soft tissue image contrast. Rapid and accurate segmentation of organs at risk (OAR) is a crucial step in MR image-guided RT. In this paper, we propose a fully automated two-step convolutional neural network (CNN) approach to delineate multiple OARs from T2-weighted (T2W) MR images.

METHODS

We employ a coarse-to-fine segmentation strategy. The coarse segmentation step first identifies the approximate boundary of each organ of interest and crops the MR volume around the centroid of organ-specific region of interest (ROI). The cropped ROI volumes are then fed to organ-specific fine segmentation networks to produce detailed segmentation of each organ. A three-dimensional (3-D) U-Net is trained to perform the coarse segmentation. For the fine segmentation, a 3-D Dense U-Net is employed in which a modified 3-D dense block is incorporated into the 3-D U-Net-like network to acquire inter and intra-slice features and improve information flow while reducing computational complexity. Two sets of T2W MR images (221 cases for MR1 and 62 for MR2) were taken with slightly different imaging parameters and used for our network training and test. The network was first trained on MR1 which was a larger sample set. The trained model was then transferred to the MR2 domain via a fine-tuning approach. Active learning strategy was utilized for selecting the most valuable data from MR2 to be included in the adaptation via transfer learning.

RESULTS

The proposed method was tested on 20 MR1 and 32 MR2 test sets. Mean ± SD dice similarity coefficients are 0.93 ± 0.04, 0.87 ± 0.03, and 0.80 ± 0.10 on MR1 and 0.94 ± 0.05, 0.88 ± 0.04, and 0.80 ± 0.05 on MR2 for bladder, rectum, and sigmoid, respectively. Hausdorff distances (95th percentile) are 4.18 ± 0.52, 2.54 ± 0.41, and 5.03 ± 1.31 mm on MR1 and 2.89 ± 0.33, 2.24 ± 0.40, and 3.28 ± 1.08 mm on MR2, respectively. The performance of our method is superior to other state-of-the-art segmentation methods.

CONCLUSIONS

We proposed a two-step CNN approach for fully automated segmentation of female pelvic MR bladder, rectum, and sigmoid from T2W MR volume. Our experimental results demonstrate that the developed method is accurate, fast, and reproducible, and outperforms alternative state-of-the-art methods for OAR segmentation significantly (p < 0.05).

Assessing radiation oncology research needs in India: Results of a physician survey

Background

In India, where the annual incidence of cancer is projected to reach 1.7 million by 2020, the need for clinical research to establish the most effective, resource-guided, and evidence-based care is paramount. In this study, we sought to better understand the research training needs of radiation oncologists in India.

Methods

A 12 item questionnaire was developed to assess research training needs and was distributed at the research methods course jointly organized by Indian College of Radiation Oncology, the American Brachytherapy Society, and Education Committee of the American Society of Therapeutic Radiation Oncology during the Indian Cancer Congress, 2017.

Results

Of 100 participants who received the questionnaire, 63% responded. Ninety percent (56/63) were Radiation Oncologists. Forty-two percent (26/63) of respondents had previously conducted research. A longer length of practice (>10 years) was significantly associated with conducting research (odds ratio (OR) 6.99, P = 0.031) and having formal research training trended toward significance (OR 3.03, P = 0.058). The most common reason for not conducting research was "lack of training" (41%, 14/34). The most common types of research conducted were Audits and Retrospective studies (62%, 16/26), followed by a Phase I/II/III Trial (46%, 10/26). Having formal research training was a significant factor associated with writing a protocol (OR 5.53, P = 0.016). Limited training in research methods (54%, 13/24) and lack of mentorship (42%, 10/24) were cited as reasons for not developing a protocol. Ninety-seven percent (57/59) of respondents were interested in a didactic session on research, specifically focusing on biostatistics.

Conclusions

With research training and mentorship, there is a greater likelihood that concepts and written protocols will translate into successfully completed studies in radiation therapy.

On the impact of absorbed dose specification, tissue heterogeneities, and applicator heterogeneities on Monte Carlo-based dosimetry of Ir-192, Se-75, and Yb-169 in conventional and intensity-modulated brachytherapy for the treatment of cervical cancer

PURPOSE

The purpose of this study was to evaluate the impact of dose reporting schemes and tissue/applicator heterogeneities for ¹⁹² Ir-, ⁷⁵ Se-, and ¹⁶⁹ Yb-based MRI-guided conventional and intensity-modulated brachytherapy.

METHODS AND MATERIALS

Treatment plans using a variety of dose reporting and tissue/applicator segmentation schemes were generated for a cohort (n = 10) of cervical cancer patients treated with ¹⁹² Ir-based Venezia brachytherapy. Dose calculations were performed using RapidBrachyMCTPS, a Geant4-based research Monte Carlo treatment planning system. Ultimately, five dose calculation scenarios were evaluated: (a) dose to water in water (D_w,w ); (b) D_w,w taking the applicator material into consideration (D_w,wApp ); (c) dose to water in medium (D_w,m ); (d and e) dose to medium in medium with mass densities assigned either nominally per structure (D_{m,m (Nom)} ) or voxel-by-voxel (D_m,m ).

RESULTS

Ignoring the plastic Venezia applicator (D_w,wApp ) overestimates D_m,m by up to 1% (average) with high energy source (¹⁹² Ir and ⁷⁵ Se) and up to 2% with ¹⁶⁹ Yb. Scoring dose to water (D_w,wApp or D_w,m ) generally overestimates dose and this effect increases with decreasing photon energy. Reporting dose other than D_m,m (or D_{m,m Nom} ) for ¹⁶⁹ Yb-based conventional and intensity-modulated brachytherapy leads to a simultaneous overestimation (up to 4%) of CTV_HR D₉₀ and underestimation (up to 2%) of bladder D_2cc due to a significant dip in the mass-energy absorption ratios at the depths of nearby targets and OARs. Using a nominal mass-density assignment per structure, rather than a CT-derived voxel-by-voxel assignment for MRI-guided brachytherapy, amounts to a dose error up to 1% for all radionuclides considered.

CONCLUSIONS

The effects of the considered dose reporting schemes trend correspondingly between conventional and intensity-modulated brachytherapy. In the absence of CT-derived mass densities, MRI-only-based dosimetry can adequately approximate D_m,m by assigning nominal mass densities to structures. Tissue and applicator heterogeneities do not significantly impact dosimetry for ¹⁹² Ir and ⁷⁵ Se, but do for ¹⁶⁹ Yb; dose reporting must be explicitly defined since D_w,m and D_w,w may overstate the dosimetric benefits.

Porphyria cutanea tarda exacerbation as a paraneoplastic syndrome in vaginal cancer resolved with chemoradiation

Porphyria Cutanea Tarda (PCT) is a rare paraneoplastic syndrome. The effects of therapeutic ionizing radiation in patients with PCT are not well understood. We report the case of a 55 year-old woman with a past medical history significant for kidney transplant with rejection and removal on hemodialysis, Stevens-Johnson syndrome, porphyria cutanea tarda, undifferentiated connective tissue disease probably systemic lupus, and hepatitis C, who underwent curative chemoradiation treatment for a recurrent vaginal squamous cell carcinoma. There was no increased acute toxicity and active porphyria cutanea tarda improved over the course of radiation treatment and fully resolved within 1 year. However, there was significant myofibrotic late toxicity within the treated region.

Vaginal necrosis: A rare late toxicity after radiation therapy

Vaginal necrosis is a late radiation tissue injury with serious morbidity complications. It is rare, and its incidence is not well assessed in prospective trials. Patient comorbidities and radiation dose can significantly increase the risk. As treatment of gynecologic malignancies often involve a multidisciplinary approach, timely diagnosis and appropriate management by physicians of the team are crucial. Untreated vaginal necrosis can lead to infection, hemorrhage, necrosis-related fistulation to the bladder or rectum, perforation, and death. In this review, we describe the pathophysiology of vaginal necrosis, its clinical course, and management options.