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.

Phase 1/2 trial evaluating the effectiveness and safety of dose-adapted Hypofractionated pelvic radiotherapy for Advanced Cervical cancers INeligible for ChemoTherapy (HYACINCT)

BACKGROUND

The standard treatment for locally advanced cervical cancer (LACC) is concurrent chemoradiation (CRT) followed by brachytherapy (BRT). The addition of chemotherapy (ChT) to radiotherapy (RT) is associated with a 7.5% improvement in overall survival but with more grade 3-4 acute toxicities (16.4% vs 4.9%, CRT vs RT alone). The risk-benefit ratio could be less favorable in advanced disease with renal dysfunction secondary to tumor-related hydronephrosis; borderline cardiac function; and frail patients. RT alone followed by BRT achieves long-term locoregional control <62%. Hypofractionated RT (HF-RT) using older techniques result in comparable disease control and low late toxicity rates (4-8%). Dose-adapted HF-RT using intensity-modulated RT with nodal simultaneous integrated boost (nSIB) could improve tumor control and toxicity, when ChT is contraindicated.

METHODS

The HYACINCT study is a two-phase study to determine the effectiveness and safety of HF-RT with nSIB in LACC when ChT is contraindicated. Phase 1 is a dose-escalation study using standard 3 + 3 design, to determine the maximum tolerated dose (MTD) for nSIB in combination with pelvic HF-RT (2.67 Gy x 15 fractions). Phase 2 is a single-arm clinical trial using Simon's two-stage design, to assess the efficacy of HF-RT with nSIB in terms of tumor response. Adult women with biopsy-proven, untreated LACC, with contraindication to ChT will be included in this trial.

DISCUSSION

For the phase 1, the primary endpoint is dose-limiting toxicity (DLT), or any grade ?3 acute or sub-acute toxicity. The dose level at which incidence of DLT is ?33% is defined as the maximum tolerance dose (MTD). For the phase 2, the primary endpoint is complete response at 3 months post-treatment. Secondary outcomes are progression-free and overall survival, acute and late toxicity, and patient-reported outcomes (EPIC, EORTCQLQ C30 + CX24, PGIC, PCIS). Trial registration: NCT05210270.

Radiation Planning Assistant - A Streamlined, Fully Automated Radiotherapy Treatment Planning System

The Radiation Planning Assistant (RPA) is a system developed for the fully automated creation of radiotherapy treatment plans, including volume-modulated arc therapy (VMAT) plans for patients with head/neck cancer and 4-field box plans for patients with cervical cancer. It is a combination of specially developed in-house software that uses an application programming interface to communicate with a commercial radiotherapy treatment planning system. It also interfaces with a commercial secondary dose verification software. The necessary inputs to the system are a Treatment Plan Order, approved by the radiation oncologist, and a simulation computed tomography (CT) image, approved by the radiographer. The RPA then generates a complete radiotherapy treatment plan. For the cervical cancer treatment plans, no additional user intervention is necessary until the plan is complete. For head/neck treatment plans, after the normal tissue and some of the target structures are automatically delineated on the CT image, the radiation oncologist must review the contours, making edits if necessary. They also delineate the gross tumor volume. The RPA then completes the treatment planning process, creating a VMAT plan. Finally, the completed plan must be reviewed by qualified clinical staff.

Model for Estimating Power and Downtime Effects on Teletherapy Units in Low-Resource Settings

Purpose

More than 6,500 megavoltage teletherapy units are needed worldwide, many in low-resource settings. Cobalt-60 units or linear accelerators (linacs) can fill this need. We have evaluated machine performance on the basis of patient throughput to provide insight into machine viability under various conditions in such a way that conclusions can be generalized to a vast array of clinical scenarios.

Materials and Methods

Data from patient treatment plans, peer-reviewed studies, and international organizations were combined to assess the relative patient throughput of linacs and cobalt-60 units that deliver radiotherapy with standard techniques under various power and maintenance support conditions. Data concerning the frequency and duration of power outages and downtime characteristics of the machines were used to model teletherapy operation in low-resource settings.

Results

Modeled average daily throughput was decreased for linacs because of lack of power infrastructure and for cobalt-60 units because of limited and decaying source strength. For conformal radiotherapy delivered with multileaf collimators, average daily patient throughput over 8 years of operation was equal for cobalt-60 units and linacs when an average of 1.83 hours of power outage occurred per 10-hour working day. Relative to conformal treatments delivered with multileaf collimators on the respective machines, the use of advanced techniques on linacs decreased throughput between 20% and 32% and, for cobalt machines, the need to manually place blocks reduced throughput up to 37%.

Conclusion

Our patient throughput data indicate that cobalt-60 units are generally best suited for implementation when machine operation might be 70% or less of total operable time because of power outages or mechanical repair. However, each implementation scenario is unique and requires consideration of all variables affecting implementation.