A novel minimally invasive dynamic-shield, intensity-modulated brachytherapy system for the treatment of cervical cancer

PURPOSE

To present a novel, MRI-compatible dynamicshield intensity modulated brachytherapy (IMBT) applicator and delivery system using ¹⁹² Ir, ⁷⁵ Se, and ¹⁶⁹ Yb radioisotopes for the treatment of locally advanced cervical cancer. Needle-free IMBT is a promising technique for improving target coverage and organs at risk (OAR) sparing.

METHODS AND MATERIALS

The IMBT delivery system dynamically controls the rotation of a novel tungsten shield placed inside an MRI-compatible, 6-mm wide intrauterine tandem. Using 36 cervical cancer cases, conventional intracavitary brachytherapy (IC-BT) and intracavitary/interstitial brachytherapy (IC/IS-BT) (10Ci ¹⁹² Ir) plans were compared to IMBT (10Ci ¹⁹² Ir; 11.5Ci ⁷⁵ Se; 44Ci ¹⁶⁹ Yb). All plans were generated using the Geant4-based Monte Carlo dose calculation engine, RapidBrachyMC. Treatment plans were optimized then normalized to the same high-risk clinical target volume (HR-CTV) D₉₀ and the D_2cc for bladder, rectum, and sigmoid in the research brachytherapy planning system, RapidBrachyMCTPS. Plans were renormalized until either of the three OAR reached dose limits to calculate the maximum achievable HR-CTV D₉₀ and D₉₈ .

RESULTS

Compared to IC-BT, IMBT with either of the three radionuclides significantly improves the HR-CTV D₉₀ and D₉₈ by up to 5.2% ± 0.3% (P < 0.001) and 6.7% ± 0.5% (P < 0.001), respectively, with the largest dosimetric enhancement when using ¹⁶⁹ Yb followed by ⁷⁵ Se and then ¹⁹² Ir. Similarly, D_2cc for all OAR improved with IMBT by up to 7.7% ± 0.6% (P < 0.001). For IC/IS-BT cases, needle-free IMBT achieved clinically acceptable plans with ¹⁶⁹ Yb-based IMBT further improving HR-CTV D₉₈ by 1.5% ± 0.2% (P = 0.034) and decreasing sigmoid D_2cc by 1.9% ± 0.4% (P = 0.048). Delivery times for IMBT are increased by a factor of 1.7, 3.3, and 2.3 for ¹⁹² Ir, ⁷⁵ Se, and ¹⁶⁹ Yb, respectively, relative to conventional ¹⁹² Ir BT.

CONCLUSIONS

Dynamic shield IMBT provides a promising alternative to conventional IC- and IC/IS-BT techniques with significant dosimetric enhancements and even greater improvements with intermediate energy radionuclides. The ability to deliver a highly conformal, OAR-sparing dose without IS needles provides a simplified method for improving the therapeutic ratio less invasively and in a less resource intensive manner.

Aiming for 100% Local Control in Locally Advanced Cervical Cancer: The Role of Complex Brachytherapy Applicators and Intraprocedural Imaging

The use of brachytherapy for the treatment of gynecologic malignancies, particularly cervical cancer, has a long and rich history that is nearly as long as the history of radiation oncology itself. From the first gynecologic brachytherapy treatments in the early 20th century to the modern era, significant transformation has occurred driven largely by advancements in technology. The development of high-dose rate sources, remote afterloaders, novel applicators, and 3-dimensional image guidance has led to improved local control, and thus improved survival, solidifying the role of brachytherapy as an integral component in the treatment of locally advanced cervical cancer. Current research efforts examining novel magnetic resonance imaging sequences, active magnetic resonance tracking, and the application of hydrogel aim to further improve local control and reduce treatment toxicity.

The ABS brachytherapy schools

The American Brachytherapy Society brachytherapy schools have been pivotal in teaching and evolving the art of brachytherapy over the past decades. Founded in 1995, the schools have consistently provided content for the major disease sites including gynecologic, prostate, and breast with ocular, vascular, head and neck, pediatric, intraluminal, systemic, and intraoperative approaches more selectively addressed. In addition, Physics schools, either coupled with clinical schools or as stand-alone venues, have provided an essential educational component for practicing physicists, a pivotal part of the brachytherapy team. Celebrating 25 years in existence, this historical overview of the American Brachytherapy Society brachytherapy schools is a tribute to the many teachers who have shared their expertise, to the many students who have been enthusiastic and interactive participants, and the staff who have made it all possible, with the reward of perpetuating the important and timely art of brachytherapy.

NRG Oncology/RTOG Consensus Guidelines for Delineation of Clinical Target Volume for Intensity Modulated Pelvic Radiation Therapy in Postoperative Treatment of Endometrial and Cervical Cancer: An Update

PURPOSE

Accurate target definition is critical for the appropriate application of radiation therapy. In 2008, the Radiation Therapy Oncology Group (RTOG) published an international collaborative atlas to define the clinical target volume (CTV) for intensity modulated pelvic radiation therapy in the postoperative treatment of endometrial and cervical cancer. The current project is an updated consensus of CTV definitions, with removal of all references to bony landmarks and inclusion of the para-aortic and inferior obturator nodal regions.

METHODS AND MATERIALS

An international consensus guideline working group discussed modifications of the current atlas and areas of controversy. A document was prepared to assist in contouring definitions. A sample case abdominopelvic computed tomographic image was made available, on which experts contoured targets. Targets were analyzed for consistency of delineation using an expectation-maximization algorithm for simultaneous truth and performance level estimation with kappa statistics as a measure of agreement between observers.

RESULTS

Sixteen participants provided 13 sets of contours. Participants were asked to provide separate contours of the following areas: vaginal cuff, obturator, internal iliac, external iliac, presacral, common iliac, and para-aortic regions. There was substantial agreement for the common iliac region (sensitivity 0.71, specificity 0.981, kappa 0.64), moderate agreement in the external iliac, para-aortic, internal iliac and vaginal cuff regions (sensitivity 0.66, 0.74, 0.62, 0.59; specificity 0.989, 0.966, 0.986, 0.976; kappa 0.60, 0.58, 0.52, 0.47, respectively), and fair agreement in the presacral and obturator regions (sensitivity 0.55, 0.35; specificity 0.986, 0.988; kappa 0.36, 0.21, respectively). A 95% agreement contour was smoothed and a final contour atlas was produced according to consensus.

CONCLUSIONS

Agreement among the participants was most consistent in the common iliac region and least in the presacral and obturator nodal regions. The consensus volumes formed the basis of the updated NRG/RTOG Oncology postoperative atlas. Continued patterns of recurrence research are encouraged to refine these volumes.

Radiation therapy for gynecologic malignancies during the COVID-19 pandemic: International expert consensus recommendations

OBJECTIVE

To develop expert consensus recommendations regarding radiation therapy for gynecologic malignancies during the COVID-19 pandemic.

METHODS

An international committee of ten experts in gynecologic radiation oncology convened to provide consensus recommendations for patients with gynecologic malignancies referred for radiation therapy. Treatment priority groups were established. A review of the relevant literature was performed and different clinical scenarios were categorized into three priority groups. For each stage and clinical scenario in cervical, endometrial, vulvar, vaginal and ovarian cancer, specific recommendations regarding dose, technique, and timing were provided by the panel.

RESULTS

Expert review and discussion generated consensus recommendations to guide radiation oncologists treating gynecologic malignancies during the COVID-19 pandemic. Priority scales for cervical, endometrial, vulvar, vaginal, and ovarian cancers are presented. Both radical and palliative treatments are discussed. Management of COVID-19 positive patients is considered. Hypofractionated radiation therapy should be used when feasible and recommendations regarding radiation dose, timing, and technique have been provided for external beam and brachytherapy treatments. Concurrent chemotherapy may be limited in some countries, and consideration of radiation alone is recommended.

CONCLUSIONS

The expert consensus recommendations provide guidance for delivering radiation therapy during the COVID-19 pandemic. Specific recommendations have been provided for common clinical scenarios encountered in gynecologic radiation oncology with a focus on strategies to reduce patient and staff exposure to COVID-19.

Adjuvant therapy for early stage, endometrial cancer with lymphovascular space invasion: Is there a role for chemotherapy?

OBJECTIVES

Lymphovascular space invasion (LVSI) is an independent risk factor for recurrence and poor survival in early-stage endometrioid endometrial cancer (EEC), but optimal adjuvant treatment is unknown. We aimed to compare the survival of women with early-stage EEC with LVSI treated postoperatively with observation (OBS), radiation (RAD, external beam and/or vaginal brachytherapy), or chemotherapy (CHEMO)+/-RAD.

METHODS

This was a multi-institutional, retrospective cohort study of women with stage I or II EEC with LVSI who underwent hysterectomy+/-lymphadenectomy from 2005 to 2015 and received OBS, RAD, or CHEMO+/-RAD postoperatively. Progression-free survival and overall survival were evaluated using Kaplan-Meier estimates and Cox proportional hazards models.

RESULTS

In total, 478 women were included; median age was 64 years, median follow-up was 50.3 months. After surgery, 143 (30%) underwent OBS, 232 (48.5%) received RAD, and 103(21.5%) received CHEMO+/-RAD (95% of whom received RAD). Demographics were similar among groups, but those undergoing OBS had lower stage and grade. A total of 101 (21%) women recurred. Progression-free survival (PFS) was improved in both CHEMO+/-RAD (HR = 0.18, 95% CI: 0.09-0.39) and RAD (HR = 0.31, 95% CI: 0.18-0.54) groups compared to OBS, though neither adjuvant therapy was superior to the other. However, in grade 3 tumors, the CHEMO+/-RAD group had superior PFS compared to both RAD (HR 0.25; 95% CI: 0.12-0.52) and OBS cohorts (HR = 0.10, 95% CI: 0.03-0.32). Overall survival did not differ by treatment.

CONCLUSIONS

In early-stage EEC with LVSI, adjuvant therapy improved PFS compared to observation alone. In those with grade 3 EEC, adjuvant chemotherapy with or without radiation improved PFS compared to observation or radiation alone.

American Brachytherapy Society working group report on the patterns of care and a literature review of reirradiation for gynecologic cancers

PURPOSE

Recurrences of previously irradiated gynecological malignancies are uncommon. Standardized management of these cases is not well established. We aim to provide an in-depth literature review and present current practice patterns among an international group of experienced practitioners in the reirradiation setting of gynecologic cancers.

METHODS AND MATERIALS

An extensive literature search was performed and 35 articles were selected based on preset criteria. A 20-question online survey of 10 experts regarding their retreatment practices was also conducted.

RESULTS

The reviewed publications include a diverse group of patients, multiple treatment techniques, a range of total doses, local control, overall survival, and toxicity outcomes. Overall, local control ranged from 44% to 88% over 1-5 years with OS in the range of 39.5-82% at 2-5 years. Late G3-4 toxicity varied very broadly from 0% to 42.9%, with most papers reporting serious toxicities greater than 15%. The most common reirradiation technique utilized was brachytherapy. Some low-dose-rate data suggest improved outcomes with doses >50 Gy. The high-dose-rate data are more varied with some studies suggesting improved local control with doses >40 Gy. In general, a longer time interval between the first and second course of radiation as well as recurrences <2-4 cm tend to have improved outcomes.

CONCLUSIONS

Reirradiation with brachytherapy results in relatively reasonable local control and toxicities for women with recurrent gynecologic cancers. The appropriate dose for each case needs to be individualized given the heterogeneity of cases. Multidisciplinary management is critical to develop individualized plans and to clearly communicate potential side effects and expected treatment outcomes.

TAKE HOME MESSAGE

Reirradiation with brachytherapy is an acceptable effective organ preserving approach for recurrent gynecologic cancers with a reasonable local control and toxicity profile. Each case requires multidisciplinary management to develop an individualized approach. Monitoring for potential long-term toxicities is essential.

Image-Guided Gynecologic Brachytherapy for Cervical Cancer

The incorporation of magnetic resonance imaging in brachytherapy has resulted in an increased use of interstitial catheters in order to create a comprehensive treatment plan that covers the visualized tumor. However, the insertion with passive, image-guidance requires estimating the location of the tumor during the insertion process, rather than visualizing and inserting the catheters directly to the desired location under active tracking. In order to treat residual disease, multiparametric MR sequences can enhance the information available to the clinician. The precision availed by MR-guided brachytherapy results in substantial improvements in needle positioning, and resulting treatment plans.

Technical assessment of a mobile CT scanner for image-guided brachytherapy

PURPOSE

The imaging performance and dose of a mobile CT scanner (Brainlab Airo®, Munich, Germany) is evaluated, with particular consideration to assessment of technique protocols for image-guided brachytherapy.

METHOD

Dose measurements were performed using a 100-mm-length pencil chamber at the center and periphery of 16- and 32-cm-diameter CTDI phantoms. Hounsfield unit (HU) accuracy and linearity were assessed using materials of specified electron density (Gammex RMI, Madison, WI), and image uniformity, noise, and noise-power spectrum (NPS) were evaluated in a 20-cm-diameter water phantom as well as an American College of Radiology (ACR) CT accreditation phantom (Model 464, Sun Nuclear, Melbourne, FL). Spatial resolution (modulation transfer function, MTF) was assessed with an edge-spread phantom and visually assessed with respect to line-pair patterns in the ACR phantom and in structures of interest in anthropomorphic phantoms. Images were also obtained on a diagnostic CT scanner (Big Bore CT simulator, Philips, Amsterdam, Netherlands) for qualitative and quantitative comparison. The manufacturer's metal artifact reduction (MAR) algorithm was assessed in an anthropomorphic body phantom containing surgical instrumentation. Performance in application to brachytherapy was assessed with a set of anthropomorphic brachytherapy phantoms - for example, a vaginal cylinder and interstitial ring and tandem.

RESULT

Nominal dose for helical and axial modes, respectively, was 56.4 and 78.9 mGy for the head protocol and 17.8 and 24.9 mGy for the body protocol. A high degree of HU accuracy and linearity was observed for both axial and helical scan modes. Image nonuniformity (e.g., cupping artifact) in the transverse (x,y) plane was less than 5 HU, but stitching artifacts (~5 HU) in the longitudinal (z) direction were observed in axial scan mode. Helical and axial modes demonstrated comparable spatial resolution of ~5 lp/cm, with the MTF reduced to 10% at ~0.38 mm-1 . Contrast-to-noise ratio was suitable to soft-tissue visualization (e.g., fat and muscle), but windmill artifacts were observed in helical mode in relation to high-frequency bone and metal. The MAR algorithm provided modest improvement to image quality. Overall, image quality appeared suitable to relevant clinical tasks in intracavitary and interstitial (e.g., gynecological) brachytherapy, including visualization of soft-tissue structures in proximity to the applicators.

CONCLUSION

The technical assessment highlighted key characteristics of dose and imaging performance pertinent to incorporation of the mobile CT scanner in clinical procedures, helping to inform clinical deployment and technique protocol selection in brachytherapy. For this and other possible applications, the work helps to identify protocols that could reduce radiation dose and/or improve image quality. The work also identified areas for future improvement, including reduction of stitching, windmill, and metal artifacts.

Brachytherapy: An overview for clinicians

Brachytherapy is a specific form of radiotherapy consisting of the precise placement of radioactive sources directly into or next to the tumor. This technique is indicated for patients affected by various types of cancers. It is an optimal tool for delivering very high doses to the tumor focally while minimizing the probability of normal tissue complications. Physicians from a wide range of specialties may be involved in either the referral to or the placement of brachytherapy. Many patients require brachytherapy as either primary treatment or as part of their oncologic care. On the basis of high-level evidence from randomized controlled trials, brachytherapy is mainly indicated: 1) as standard in combination with chemoradiation in patients with locally advanced cervical cancer; 2) in surgically treated patients with uterine endometrial cancer for decreasing the risk of vaginal vault recurrence; 3) in patients with high-risk prostate cancer to perform dose escalation and improve progression-free survival; and 4) in patients with breast cancer as adjuvant, accelerated partial breast irradiation or to boost the tumor bed. In this review, the authors discuss the clinical relevance of brachytherapy with a focus on indications, levels of evidence, and results in the overall context of radiation use for patients with cancer.

Comparison of treatment planning approaches for spatially fractionated irradiation of deep tumors

Purpose

The purpose of this work was to compare the dosimetry and delivery times of 3D‐conformal (3DCRT)‐, volumetric modulated arc therapy (VMAT)‐, and tomotherapy‐based approaches for spatially fractionated radiation therapy for deep tumor targets.

Methods

Two virtual GRID phantoms were created consisting of 7 “target” cylinders (1‐cm diameter) aligned longitudinally along the tumor in a honey‐comb pattern, mimicking a conventional GRID block, with 2‐cm center‐to‐center spacing (GRID_2 cm) and 3‐cm center‐to‐center spacing (GRID_3 cm), all contained within a larger cylinder (8 and 10 cm in diameter for the GRID_2 cm and GRID_3 cm, respectively). In a single patient, a GRID_3 cm structure was created within the gross tumor volume (GTV). Tomotherapy, VMAT (6 MV + 6 MV‐flattening‐filter‐free) and multi‐leaf collimator segment 3DCRT (6 MV) plans were created using commercially available software. Two tomotherapy plans were created with field widths (TOMO_2.5 cm) 2.5 cm and (TOMO_5 cm) 5 cm. Prescriptions for all plans were set to deliver a mean dose of 15 Gy to the GRID targets in one fraction. The mean dose to the GRID target and the heterogeneity of the dose distribution (peak‐to‐valley and peak‐to‐edge dose ratios) inside the GRID target were obtained. The volume of normal tissue receiving 7.5 Gy was determined.

Results

The peak‐to‐valley ratios for GRID_2 cm/GRID_3 cm/Patient were 2.1/2.3/2.8, 1.7/1.5/2.8, 1.7/1.9/2.4, and 1.8/2.0/2.8 for the 3DCRT, VMAT, TOMO_5 cm, and TOMO_2.5 cm plans, respectively. The peak‐to‐edge ratios for GRID_2 cm/GRID_3 cm/Patient were 2.8/3.2/5.4, 2.1/1.8/5.4, 2.0/2.2/3.9, 2.1/2.7/5.2 and for the 3DCRT, VMAT, TOMO_5 cm, and TOMO_2.5 cm plans, respectively. The volume of normal tissue receiving 7.5 Gy was lowest in the TOMO_2.5 cm plan (GRID_2 cm/GRID_3 cm/Patient = 54 cm³/19 cm³/10 cm³). The VMAT plans had the lowest delivery times (GRID_2 cm/GRID_3 cm/Patient = 17 min/8 min/9 min).

Conclusion

Our results present, for the first time, preliminary evidence comparing IMRT‐GRID approaches which result in high‐dose “islands” within a target, mimicking what is achieved with a conventional GRID block but without high‐dose “tail” regions outside of the target. These approaches differ modestly in their ability to achieve high peak‐to‐edge ratios and also differ in delivery times.

Association of a Simulated Institutional Gender Equity Initiative With Gender-Based Disparities in Medical School Faculty Salaries and Promotions

IMPORTANCE

Despite progress in narrowing gender-based salary gaps, notable disparities persist in the scientific community. The significance of pay difference may be underestimated, with little data evaluating its effect on lifetime wealth after accounting for factors like time to promotion and savings.

OBJECTIVES

To characterize gender disparities in salary and assess the outcomes associated with a gender equity initiative (GEI).

DESIGN, SETTING, AND PARTICIPANTS

Quality improvement study with simulations of salary and additional accumulated wealth (AAW) using retrospectively reviewed Johns Hopkins University School of Medicine annual salary and promotion data. All academic faculty were included in the faculty salary analysis from 2005 (n = 1481) and 2016 (n = 1885).

MAIN OUTCOMES AND MEASURES

Salary and longitudinal promotion data from 2005 to 2016 were used to estimate gender-based differences in salary and time to promotion. The effect of these differences on total salary and AAW, including retirement and salary-based investments, was simulated for a representative male and female faculty member over a 30-year career in 3 scenarios: (1) pre-GEI, (2) post-GEI, and (3) in real time for GEI, beginning with and progressing through these initiatives.

RESULTS

Analyses of salaries of 1481 faculty (432 women) in 2005 and 1885 faculty (742 women) in 2016 revealed that a decade after GEI implementation, the overall mean (SE) salary gap by gender decreased from -2.6% (1.2%) (95% CI, -5.6% to -0.3%) to -1.9% (1.1%) (95% CI, -4.1% to 0.3%). Simulation of pre-GEI disparities correlated with male faculty collecting an average lifetime AAW of $501 416 more than the equivalent woman, with disparities persisting past retirement. The AAW gap decreased to $210 829 in the real-time GEI simulation and to $66 104 using post-GEI conditions, reflecting success of GEI efforts.

CONCLUSIONS AND RELEVANCE

Even small gender-based salary gaps are associated with substantial differences in lifetime wealth, but an institutional commitment to achieving equitable promotion and compensation for women can appreciably reduce these disparities. The findings of this study support broad implementation of similar initiatives without delay, as results may take more than a decade to emerge. A modifiable version of the simulation is provided so that external users may assess the potential disparities present within their own institutions.

Adjuvant therapy after radical trachelectomy for stage I cervical cancer

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Radical trachelectomy is a fertility sparing option for select stage I cervical patients.

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Indications for adjuvant treatment following trachelectomy are based on standard recommendations following hysterectomy.

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Case report outlining specifics of imaged-guided brachytherapy as part of the adjuvant treatment after trachelectomy.

Impact of Human Immunodeficiency Virus Infection on Survival and Acute Toxicities From Chemoradiation Therapy for Cervical Cancer Patients in a Limited-Resource Setting

PURPOSE

To prospectively compare survival between human immunodeficiency virus (HIV)-infected versus HIV-uninfected cervical cancer patients who initiated curative chemoradiation therapy (CRT) in a limited-resource setting.

METHODS AND MATERIALS

Women with locally advanced cervical cancer with or without HIV infection initiating radical CRT in Botswana were enrolled in a prospective, observational, cohort study from July 2013 through January 2015.

RESULTS

Of 182 women treated for cervical cancer during the study period, 143 women initiating curative CRT were included in the study. Eighty-five percent of the participants (122 of 143) had stage II/III cervical cancer, and 67% (96 of 143) were HIV-infected. All HIV-infected patients were receiving antiretroviral therapy (ART) at the time of curative cervical cancer treatment initiation. We found no difference in toxicities between HIV-infected and HIV-uninfected women. The 2-year overall survival (OS) rates were 65% for HIV-infected women (95% confidence interval [CI] 54%-74%) and 66% for HIV-uninfected women (95% CI 49%-79%) (P = .70). Factors associated with better 2-year OS on multivariate analyses included baseline hemoglobin >10 g/dL (hazard ratio [HR] 0.37, 95% CI 0.19-0.72, P = .003), total radiation dose ≥75 Gy (HR 0.52, 95% CI 0.27-0.97, P = .04), and age <40 years versus 40-59 years (HR 2.17, 95% CI 1.05-4.47, P = .03).

CONCLUSIONS

Human immunodeficiency virus status had no effect on 2-year OS or on acute toxicities in women with well-managed HIV infection who initiated curative CRT in Botswana. In our cohort, we found that baseline hemoglobin levels, total radiation dose, and age were associated with survival, regardless of HIV status.

HIV Infection and Survival Among Women With Cervical Cancer

Purpose Cervical cancer is the leading cause of cancer death among the 20 million women with HIV worldwide. We sought to determine whether HIV infection affected survival in women with invasive cervical cancer. Patients and Methods We enrolled sequential patients with cervical cancer in Botswana from 2010 to 2015. Standard treatment included external beam radiation and brachytherapy with concurrent cisplatin chemotherapy. The effect of HIV on survival was estimated by using an inverse probability weighted marginal Cox model. Results A total of 348 women with cervical cancer were enrolled, including 231 (66.4%) with HIV and 96 (27.6%) without HIV. The majority (189 [81.8%]) of women with HIV received antiretroviral therapy before cancer diagnosis. The median CD4 cell count for women with HIV was 397 (interquartile range, 264 to 555). After a median follow-up of 19.7 months, 117 (50.7%) women with HIV and 40 (41.7%) without HIV died. One death was attributed to HIV and the remaining to cancer. Three-year survival for the women with HIV was 35% (95% CI, 27% to 44%) and 48% (95% CI, 35% to 60%) for those without HIV. In an adjusted analysis, HIV infection significantly increased the risk for death among all women (hazard ratio, 1.95; 95% CI, 1.20 to 3.17) and in the subset that received guideline-concordant curative treatment (hazard ratio, 2.63; 95% CI, 1.05 to 6.55). The adverse effect of HIV on survival was greater for women with a more-limited stage cancer ( P = .035), those treated with curative intent ( P = .003), and those with a lower CD4 cell count ( P = .036). Advanced stage and poor treatment completion contributed to high mortality overall. Conclusion In the context of good access to and use of antiretroviral treatment in Botswana, HIV infection significantly decreases cervical cancer survival.

Prospective Clinical Implementation of a Novel Magnetic Resonance Tracking Device for Real-Time Brachytherapy Catheter Positioning

PURPOSE

We designed and built dedicated active magnetic resonance (MR)-tracked (MRTR) stylets. We explored the role of MRTR in a prospective clinical trial.

METHODS AND MATERIALS

Eleven gynecologic cancer patients underwent MRTR to rapidly optimize interstitial catheter placement. MRTR catheter tip location and orientation were computed and overlaid on images displayed on in-room monitors at rates of 6 to 16 frames per second. Three modes of actively tracked navigation were analyzed: coarse navigation to the approximate region around the tumor; fine-tuning, bringing the stylets to the desired location; and pullback, with MRTR stylets rapidly withdrawn from within the catheters, providing catheter trajectories for radiation treatment planning (RTP). Catheters with conventional stylets were inserted, forming baseline locations. MRTR stylets were substituted, and catheter navigation was performed by a clinician working inside the MRI bore, using monitor feedback.

RESULTS

Coarse navigation allowed repositioning of the MRTR catheters tips by 16 mm (mean), relative to baseline, in 14 ± 5 s/catheter (mean ± standard deviation [SD]). The fine-tuning mode repositioned the catheter tips by a further 12 mm, in 24 ± 17 s/catheter. Pullback mode provided catheter trajectories with RTP point resolution of ∼1.5 mm, in 1 to 9 s/catheter.

CONCLUSIONS

MRTR-based navigation resulted in rapid and optimal placement of interstitial brachytherapy catheters. Catheters were repositioned compared with the initial insertion without tracking. In pullback mode, catheter trajectories matched computed tomographic precision, enabling their use for RTP.

Cervical cancer in low and middle income countries: Addressing barriers to radiotherapy delivery

The global cervical cancer burden falls disproportionately upon women in low and middle-income countries. Insufficient infrastructure, lack of access to preventive HPV vaccines, screening, and treatment, as well as limited trained personnel and training opportunities, continue to impede efforts to reduce incidence and mortality in these nations. These hurdles have been substantial challenges to radiation delivery in particular, preventing treatment for a disease in which radiation is a cornerstone of curative therapy. In this review, we discuss the breadth of these barriers, while illustrating the need for adaptive approaches by proposing the use of brachytherapy alone in the absence of available external beam radiotherapy. Such modifications to current guidelines are essential to maximize radiation treatment for cervical cancer in limited resource settings.

Rectum and bladder spacing in cervical cancer brachytherapy using a novel injectable hydrogel compound

PURPOSE

The aim of this study was to evaluate injection of a novel hydrogel (TraceIT; Augmenix, Waltham, MA) between the cervix, rectum, and bladder in female cadavers compared with, and in addition to, the current standard of gauze packing, for organ-at-risk sparing in cervical cancer brachytherapy planning.

METHODS AND MATERIALS

This brachytherapy cadaver study used T2-weighted MRI and CT imaging to compare three scenarios: (1) gauze packing alone, (2) hydrogel injection placed in the cervical fornices and rectovaginal septum, and (3) gauze packing in conjunction with hydrogel injection. Hydrogel distribution was evaluated. Doses to 2 cm³ volumes (D_2cc) for the rectum, bladder, and sigmoid were collected. Statistical significance (p < 0.05) was evaluated using a two-tailed paired t test.

RESULTS

Hydrogel was successfully injected to space the bladder and rectum from the cervix in all five cadavers. The spacer was easily identifiable on both CT and MRI. The use of hydrogel in addition to packing resulted in a 22% decrease in rectum D_2cc dose (p = 0.02), a 10% decrease in bladder D_2cc (p = 0.27), and no change in sigmoid D_2cc dose. No difference was observed between hydrogel only vs. gauze packing only.

CONCLUSIONS

Our results revealed a significant clinically meaningful decrease in rectal D_2cc associated with the use of hydrogel in addition to gauze packing-TraceIT hydrogel holds promise as a spacer in cervical cancer therapy.

MR- versus CT-based high-dose-rate interstitial brachytherapy for vaginal recurrence of endometrial cancer

PURPOSE

To compare clinical outcomes of MR-based versus CT-based high-dose-rate interstitial brachytherapy (ISBT) for vaginal recurrence of endometrioid endometrial cancer (EC).

METHODS AND MATERIALS

We reviewed 66 patients with vaginal recurrent EC; 18 had MR-based ISBT on a prospective clinical trial and 48 had CT-based treatment. Kaplan-Meier survival modeling was used to generate estimates for local control (LC), disease-free interval (DFI), and overall survival (OS), and multivariate Cox modeling was used to assess prognostic factors. Toxicities were evaluated and compared.

RESULTS

Median followup was 33 months (CT 30 months, MR 35 months). Median cumulative equivalent dose in 2-Gy fractions was 75.5 Gy for MR-ISBT and 73.8 Gy for CT-ISBT (p = 0.58). MR patients were older (p = 0.03) and had larger tumor size (>4 cm vs. ≤ 4 cm) compared to CT patients (p = 0.04). For MR-based versus CT-based ISBT, 3-year KM rate for local control was 100% versus 78% (p = 0.04), DFI was 69% versus 55% (p = 0.1), and OS was 63% versus 75% (p = 0.81), respectively. On multivariate analysis, tumor Grade 3 was associated with worse OS (HR 3.57, 95% CI 1.25, 11.36) in a model with MR-ISBT (HR 0.56, 95% CI 0.16, 1.89). Toxicities were not significantly different between the two modalities.

CONCLUSION

Despite worse patient prognostic features, MR-ISBT was associated with a significantly better (100%) 3-year local control, comparable survival, and improved DFI rates compared to CT. Toxicities did not differ compared to CT-ISBT patients. Tumor grade contributed as the most significant predictor for survival. Larger prospective studies are needed to assess the impact of MR-ISBT on survival outcomes.