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

Monte Carlo simulated correction factors for high dose rate brachytherapy postal dosimetry audit methodology

Background and Purpose

Full-scatter conditions in water are impractical for postal dosimetry audits in brachytherapy. This work presents a method to obtain correction factors that account for deviations from full-scatter water-equivalent conditions for a small plastic phantom.

Material and Methods

A 16 × 8 × 3 cm phantom (PMMA) with a radiophotoluminescent dosimeter (RPLD) at the centre and two catheters on either side was simulated using Monte Carlo (MC) to calculate correction factors accounting for the lack of scatter, non-water equivalence of the RPLD and phantom, source model and backscatter for HDR 60Co and 192Ir sources.

Results

The correction factors for non-water equivalence, lack of full scatter, and the use of PMMA were 1.062 ± 0.013, 1.059 ± 0.008 and 0.993 ± 0.009 for 192Ir and 1.129 ± 0.005, 1.009 ± 0.005 and 1.005 ± 0.005 for 60Co respectively. Water-equivalent backscatter thickness of 5 cm was found to be adequate and increasing thickness of backscatter did not have an influence on the RPLD dose. The mean photon energy in the RPLD for four HDR 192Ir sources was 279 ± 2 keV in full scatter conditions and 295 ± 1 keV in the audit conditions. For 60Co source the corresponding mean energies were 989 ± 1 keV and 1022 ± 1 keV respectively.

Conclusions

Correction factors were obtained through the MC simulations for conditions deviating from TG-43, including the amount of back scatter, and the optimum audit set up. Additionally, the influence of different source models on the correction factors was negligible and demonstrates their generic applicability.

Clinical outcomes of single application multi-fractionated CT-guided interstitial high-dose-rate brachytherapy for locally advanced cervical cancer: A multi-institution initial experience

Purpose

The aim of the study was to evaluate the safety and clinical outcomes of single application multi-fractionated computed tomography (CT)-guided interstitial high-dose-rate brachytherapy given in four fractions in locally advanced cervical cancer.

Material and methods

Patients with locally advanced cervical cancer stage IIB-IVA treated definitively with external radiation ± weekly cisplatin, followed by single application multi-fractionated CT-guided interstitial high-dose-rate brachytherapy in four fractions were included. Dosimetry data, clinical response, and toxicity records were reviewed.

Results

Between January 2018 and December 2022, twenty-two patients were included. Clinical stage distribution was as follows: IIB - 13.6%, IIIB - 27.3%, IIIC - 22.7%, and IVA - 36.4%. Mean high-risk clinical target volume (HR-CTV) was 66.19 ±32.69 cm3, and HR-CTV D90 dose was 86.8 ±1.7 Gy. 2 cc doses to bladder, rectum, and sigmoid were 84.6 ±2.8 Gy, 71.5 ±2.4 Gy, and 65.6 ±4.0 Gy, respectively. Mean overall treatment time was 66 ±21 days. With a median follow-up of 11.5 months (range, 5-44 months), median survival and local control were not achieved. One-year local control rate, one-year progression-free survival, and one-year overall survival were 82%, 66%, and 78%, respectively. Univariate analysis showed overall treatment time to be the only variable associated with all oncologic outcomes. For acute toxicity, grade 3 toxicity in four patients and grade 4 toxicity of infection in one patient were observed. For late toxicity, grade 3 gastrointestinal toxicity was noted in two patients.

Conclusions

Initial results suggest that single application multi-fractionated CT-guided interstitial brachytherapy given in four fractions in locally advanced cervical cancer seems to be feasible and safe, but additional evidence is needed to generate more validated conclusions.

The American Brachytherapy Society and Indian Brachytherapy Society consensus statement for the establishment of high-dose-rate brachytherapy programs for gynecological malignancies in low- and middle-income countries

PURPOSE

The global cervical cancer burden is disproportionately high in low- and middle-income countries (LMICs), and outcomes can be governed by the accessibility of appropriate screening and treatment. High-dose-rate (HDR) brachytherapy plays a central role in cervical cancer treatment, improving local control and overall survival. The American Brachytherapy Society (ABS) and Indian Brachytherapy Society (IBS) collaborated to provide this succinct consensus statement guiding the establishment of brachytherapy programs for gynecological malignancies in resource-limited settings.

METHODS AND MATERIALS

ABS and IBS members with expertise in brachytherapy formulated this consensus statement based on their collective clinical experience in LMICs with varying levels of resources.

RESULTS

The ABS and IBS strongly encourage the establishment of HDR brachytherapy programs for the treatment of gynecological malignancies. With the consideration of resource variability in LMICs, we present 15 minimum component requirements for the establishment of such programs. Guidance on these components, including discussion of what is considered to be essential and what is considered to be optimal, is provided.

CONCLUSIONS

This ABS/IBS consensus statement can guide the successful and safe establishment of HDR brachytherapy programs for gynecological malignancies in LMICs with varying levels of resources.

Tumor size before image-guided brachytherapy is an important factor of local control after radiotherapy for cervical squamous cell carcinoma: analysis in cases using central shielding

We analyzed the local control (LC) of cervical squamous cell carcinoma treated by computed tomography (CT)-based image-guided brachytherapy (IGBT) using central shielding (CS). We also examined the value of tumor diameter before brachytherapy (BT) as a factor of LC. In total, 97 patients were analyzed between April 2016 and March 2020. Whole-pelvic (WP) radiotherapy (RT) with CS was performed, and the total pelvic sidewall dose was 50 or 50.4 Gy; IGBT was delivered in 3-4 fractions. The total dose was calculated as the biologically equivalent dose in 2 Gy fractions, and distribution was modified manually by graphical optimization. The median follow-up period was 31.8 months (6.3-63.2 months). The 1- and 2-year LC rates were 89% and 87%, respectively. The hazard ratio was 10.11 (95% confidence interval: 1.48-68.99) for local recurrence in those with a horizontal tumor diameter ≥ 4 cm compared to those with < 4 cm before BT. In CT-based IGBT for squamous cell carcinoma, favorable LC can be obtained in patients with a tumor diameter < 4 cm before BT. However, if the tumor diameter is ≥ 4 cm, different treatment strategies such as employing interstitial-BT for dose escalation may be necessary.

Image-guided interstitial brachytherapy for recurrent cervical cancer after radiotherapy: A single institution experience

Purpose

The aim of this study is to evaluate the efficacy and toxicity of image-guided high-dose rate (HDR) interstitial brachytherapy (ISBT) for the reirradiation of cervical cancer within a previously irradiated area.

Methods and materials

Twenty-three consecutive patients with cervical cancer were reirradiated with curative intent using brachytherapy (BT) with or without external beam irradiation. The median biologically equivalent dose in 2-Gy fractions (EQD2) for reirradiation was 64.0 Gy (range: 31.3–95.1 Gy), and the median cumulative EQD2 (for primary treatment and reirradiation) was 152.4 Gy (range: 97.8–200.9 Gy). The average clinical target volume was 82.9 cm³ (range: 26.9–208.3 cm³), and the median treatment-free interval (TFI) was 13 months (range: 3–93 months).

Results

The median follow-up time was 19 months (range: 2–59 months). The complete response rate after reirradiation was 56.5%. The 1-, 2- 3-, and 4-year post-relapse survival (PRS) rates were 65.2%, 43.5%, 33.8%, and 27.1%, respectively. The median reirradiation EQD2 D2cc of rectum and bladder was 39.5 Gy (range = 14.6–96.2 Gy) and 52.1 Gy (range = 29.1–114.2 Gy). The median cumulative EQD2 D2cc of rectum and bladder was 115.0 Gy (range = 84.4–189.3 Gy) and 130.5 Gy (range = 95.5–173.5 Gy). During follow-up, nine (39.1%) patients had experienced grade 3 or 4 late toxicities. Grade ≥3 rectal toxicity occurred in three patients (13.0%). Grade ≥3 urinary toxicity occurred in five patients (21.7%). One patient (4.3%) had both grade ≥3 urinary and rectal toxicity. Tumor volume, TFI, tumor invasion organ number, and local control were significant prognostic factors adversely affecting OS.

Conclusions

For recurrent cervical cancer after radiotherapy, reirradiation of HDR-ISBT is feasible, even if the local tumor invasion is large, with a good chance of survival and acceptable side effects.

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.

Quality Assurance in Modern Gynecological HDR-Brachytherapy (Interventional Radiotherapy): Clinical Considerations and Comments

Simple Summary

This is a focused review discussing quality assurance during interventional brachytherapy in gynecological cancers. This topic is very large and is usually addressed from the technical and physical sides, therefore, we decided to select “hot-spots” under this large title and discuss them from the point of view of clinicians. We hope that this concise and focused review will help clinicians in improving their quality assurance protocols and draw attention to the discussed issues.

Abstract

The use of brachytherapy (interventional radiotherapy) in the treatment of gynecological cancers is a crucial element in both definitive and adjuvant settings. The recent developments in high-dose rate remote afterloaders, modern applicators, treatment-planning software, image guidance, and dose monitoring systems have led to improvement in the local control rates and in some cases improved the survival rates. The development of these highly advanced and complicated treatment modalities has been accompanied by challenges, which have made the existence of quality assurance protocols a must to ensure the integrity of the treatment process. Quality assurance aims at standardizing the technical and clinical procedures involved in the treatment of patients, which could eventually decrease the source of uncertainties whether technical (source/equipment related) or clinical. This commentary review sheds light (from a clinical point of view) on some potential sources of uncertainties associated with the use of modern brachytherapy in the treatment of gynecological cancers.