A randomized trial evaluating a novel hydrogel packing system compared to standard packing during image-guided high-dose rate brachytherapy boost for cervical cancer

INTRODUCTION

The purpose of this prospective randomized trial was to compare the use of a novel vaginal hydrogel packing system (BrachyGel) to standard vaginal packing (VP) during high dose rate (HDR) brachytherapy (BT) for locally advanced cervical cancer (LACC).

METHODS

This cross-over study included LACC patients receiving HDR BT boost (intracavitary +/- interstitial). All patients received alternating gauze or BrachyGel VP on Arms A and B. Patients, physicians, and physicists evaluated BT characteristics via a 4-point Likert scale. Adverse events (AEs) were prospectively collected and scored per CTCAE.

RESULTS

The 20 patients enrolled. The mean bladder D2cc difference between gauze and BrachyGel in Arm A was 0.117 Gray (Gy) and in Arm B 0.013 Gy. The mean difference in rectum D2cc in Arm A and Arm B was -0.189 Gy and -0.191 Gy, respectively. The mean dose to 90% of the high-risk clinical target volume (HR-CTV) for gauze compared to BrachyGel was -0.032 Gy (95% CI: 0.472, 0.409). Patient-reported discomfort was similar with BrachyGel and gauze ("mild/moderate" 70.0% vs 74.0%, respectively). The clarity of VP was similar between BrachyGel and gauze (86.8% vs 89.7%, respectively). The completeness of VP was more frequently "excellent/good" with BrachyGel (79.0%) compared to gauze (56.4%). The ease of packing was more frequently "extremely easy" with BrachyGel (21.2% vs 0%). No serious AEs were reported.

CONCLUSION

This randomized trial found no clinically significant difference in OAR or HR-CTV dosimetry between BrachyGel and standard VP. BrachyGel performed well compared to gauze for the patient and physician use experience.

Impact of Lymphopenia on Definitive Treatment of Locally Advanced Cervical Cancer

PURPOSE/OBJECTIVE(S)

Pre-treatment lymphopenia prior to initiating treatment has been correlated with reduced survival in a number of different cancers. The purpose of this study is to evaluate the association between lymphopenia and survival in women with locally advanced cervical cancer (LACC) treated with primary chemoradiation (CRT).

MATERIALS/METHODS

We retrospectively reviewed patients with LACC treated at a single institution from 2005 - 2021 with available lymphocyte information. Patient and treatment characteristics were recorded including age, tumor size and stage, EBRT dose/fractionation, and brachytherapy dosimetry data. Absolute lymphocyte counts (ALC) were collected prior to initiating CRT and at 3-month intervals following CRT and graded based on severity of lymphopenia using CTCAE v 5.0. Overall survival (OS), progression free survival (PFS), and local control (LC) were calculated from the start of treatment to date of last follow-up. Kaplan-Meier survival analysis was performed to evaluate whether lymphocyte changes were associated with OS, PFS, or LC.

RESULTS

A total of 124 patients met study inclusion criteria with stage IB - IV disease (41 stage I, 41 stage II, 36 stage III, 6 stage IV) and a median follow up of 3.6 years (range 0.2-16.5 years). The median age was 49 years (range 26-77). The median EBRT dose was 45 Gy (range: 26-57.5 Gy) and 44.2% of patients received para-aortic (PA) nodal EBRT (28.8% elective and 15.4% with positive PA nodes). 5-year OS, PFS, and LC were 60.3% (95% CI 51.5-70.7), 47.5% (95% CI 39-58), and 75.5% (95% CI 67.3-82.9), respectively. Pre-treatment lymphopenia (ALC <1000 cells/mm3) was present in 11 (9%) patients. When the total cohort was divided into patients with and without pre-treatment lymphopenia, OS was statistically improved in the patients without baseline lymphopenia, with a 5-year OS of 63.2% (95% CI 53.9-73.9) versus 35.3% (95% CI 14.5-86.3) in the lymphopenia group (p = 0.034). LC also trended to being improved in the patients without lymphopenia, though this did not reach statistical significance in our small sample size of lymphopenic patients, with 5-year LC of 76.8% (95% CI 68.4-84.3) versus 67.5% (05% CI 36.6-93.8), p = 0.45.

CONCLUSION

In this single institution experience of LACC treated with definitive CRT, we found that baseline lymphopenia is associated with inferior OS. Patients with higher pre-CRT ALC may represent a population with more robust immune systems, producing more favorable tumor responses to treatment. Additional studies are warranted to investigate the evolving role of combined EBRT and systemic therapy in LACC.

Dosimetric Analysis of Patients Treated with Stereotactic Body Radiation Therapy for Malignant Portal Vein Tumor Thrombosis Using MRI-Guided vs. CT-Guided Linear Accelerator

PURPOSE/OBJECTIVE(S)

The use of MRI-guided linear accelerators (MRI-LINAC) for radiation therapy has allowed for increased treatment precision and real-time tumor tracking. We hypothesized that the use of an MRI-LINAC, recently acquired by our institution, would allow us to treat malignant portal vein tumor thromboses (PVTT) closer to the origin of the portal vein with similar doses to the liver and nearby GI organs and with similar treatment toxicities compared to patients treated using a CT-guided linear accelerator (CT-LINAC).

MATERIALS/METHODS

We retrospectively assessed patients who received SBRT for treatment of PVTT within the UVA health system using the electronic medical record. We contoured the origin of the portal vein on the simulation scans (MRI or CT) for each patient. The shortest distance from the GTV to the portal vein origin and to organs at risk (OAR; duodenum, stomach or "other intestine") were measured. The PTV, volume of the liver receiving less than 18 Gy during treatment, and the Dmax to the portal vein origin and OAR were determined. The means for each variable were then compared between CT-LINAC and MRI-LINAC using independent samples t-tests. Treatment toxicities were graded using CTCAE version 5.0 guidelines. All plans met institutional dose constraints for SBRT.

RESULTS

A total of 6 patients treated on CT-LINAC and 3 patients treated on MRI-LINAC were identified (mean dose CT 37.7 Gy [range 21-50] in 2-5 fractions; MRI 48.3 Gy [range 45-50] in 5 fractions). The GTV was significantly closer to the portal vein origin in the MRI-LINAC group (mean CT 92.75 mm ± 45.89; MRI 32.00 mm ± 29.46; p = 0.04). The GTV trended towards being closer to OAR in the MRI-LINAC group (mean CT 43.81 mm ± 37.09; MRI 4.36 mm ± 1.85; p = 0.059). The Dmax to both the portal vein origin (mean CT 0.58 Gy ± 0.33; MRI 22.49 Gy ±24.16; p = 0.024) and OAR (mean CT 13.38 Gy ± 5.98; MRI 36.23 Gy ± 5.38; p = <0.001) was significantly higher in the MRI-LINAC group. The PTV (mean CT 152.11 cc ± 169.94; MRI 122.47 cc ± 114.65; p = 0.398) or volume of liver receiving less than 18 Gy during treatment (mean CT 1287.87 cc ± 285.20; MRI 1743.88 cc ±961.94 = 3; p = 0.147) were not significantly different between the two groups. No patients in either the MRI-LINAC or CT-LINAC group reported acute toxicities greater than Grade 1.

CONCLUSION

We found that patients with PVTT treated with MRI-LINAC SBRT at our institution were more likely to have central tumors near dose-limiting OAR. However, due to superior tumor delineation and dynamic tumor tracking, these patients were able to be treated without decreasing treatment dose or increasing acute GI toxicity compared to patients treated with CT-LINAC. A larger sample size and longer follow-up period is warranted to corroborate these initial findings.