Clinical and dosimetric consequences of imperfect applicator insertion in cervical cancer brachytherapy

Fletcher suit or ring: A comparison of Fletcher suit and ring applicators for retroverted uteri

Purpose

Approximately 20% of women worldwide have a retroverted uterus. A retroverted uterus is closer to the rectum and may cause toxicity during brachytherapy. Upon manipulation, a small percentage turn anteverted. Conventional brachytherapy applicators are designed for an anteverted uterus and can pose issues during insertion. Modified Fletcher suit and ring applicators have major differences in their geometry to achieve similar target coverage, and were analyzed in this study with respect to immediate adverse events and dosimetry.

Material and methods

Three hundred seventy-four consecutive applications performed over a 20-month period were studied retrospectively to identify intra-cavitary applications (ICAs) in retroverted uteri. Cases were divided into 2 groups: modified Fletcher suit applicator with hemi-ovoids (group A) and ring applicator (group B). D2cc for bladder and rectum were noted, and acute adverse events were recorded.

Results

Seventy-five applications were identified, out of which 47 cases used Fletcher suit applicator, and 28 cases used ring applicator. The median bladder D2cc for group A and B were 5.98 Gy and 6.3 Gy, respectively, and the median rectum D2cc was 5.27 Gy and 3.68 Gy, respectively; the median dose prescribed to point A was 6 Gy (range, 5.5-9.0 Gy). All patients had a point A coverage between 97% and 102%. Eighteen cases in both groups complained of pain requiring analgesics. Twenty-five cases (53.2%) and 20 cases (71.4%) in group A and B, respectively, required dose optimization, which was statistically insignificant (p > 0.11). A significant difference was identified (p < 0.00001) in rectal doses. A higher reported pain was noted in ring applicator group (p < 0.03). No patient experienced a profuse bleeding.

Conclusions

In most parameters, the two applicators demonstrated comparable results. The control of rectal dosage is superior in the ring applicator at the cost of higher pain incidence. Patient's comfort and rectal dose in EBRT should be taken into consideration, with preference given to the ring applicator.

The Use of 3D Printing Technology in Gynaecological Brachytherapy-A Narrative Review

Radiation therapy, including image-guided adaptive brachytherapy based on magnetic resonance imaging, is the standard of care in locally advanced cervical and vaginal cancer and part of the treatment in other primary and recurrent gynaecological tumours. Tumour control probability increases with dose and brachytherapy is the optimal technique to increase the dose to the target volume while maintaining dose constraints to organs at risk. The use of interstitial needles is now one of the quality indicators for cervical cancer brachytherapy and needles should optimally be used in ≥60% of patients. Commercially available applicators sometimes cannot be used because of anatomical barriers or do not allow adequate target volume coverage due to tumour size or topography. Over the last five to ten years, 3D printing has been increasingly used for manufacturing of customised applicators in brachytherapy, with gynaecological tumours being the most common indication. We present the rationale, techniques and current clinical evidence for the use of 3D-printed applicators in gynaecological brachytherapy.

Practical Considerations During Brachytherapy Applicator Placement for Locally Advanced Cervical Cancer

Brachytherapy is an integral part of the definitive treatment for locally advanced cervical cancer following external beam radiation therapy. Placement of brachytherapy applicators is an important skill for radiation oncologists and care must be taken to place applicators appropriately to limit complications associated with the procedure and ensure that the radiation dose sufficiently covers the target while sparing the surrounding organs at risk. Using example cases, we discuss strategies for the placement of brachytherapy applicators in patients with anatomical considerations such as large obstructing uterine fibroids and the retroverted uterus. We also discuss the management of uterine perforation during applicator placement and approaches to patients with a poor response to external beam radiation therapy before brachytherapy delivery. We draw upon the available literature and our clinical experience to suggest approaches to these challenging scenarios.

The design of an individualized cylindrical vaginal applicator with oblique guide holes using 3D modeling and printing technologies

High-dose-rate brachytherapy for cervical cancer after subtotal hysterectomy using standardized applicators cannot achieve a good absorbed-dose coverage of the target volume in special tumor morphologies and topographies due to the steep dose gradient. The aim of this pictorial essay is to present an individualized cylindrical vaginal applicator with oblique guide holes using 3D modeling and printing technologies used at the China-Japan Union Hospital of Jilin University for cervical cancer patients. We use images to describe the steps of this method.

Magnetic resonance image-based 3D volume interstitial brachytherapy using polyether ether ketone catheters in advanced cervical cancer - a feasibility study

Purpose

A feasibility study of 3D volume-based interstitial brachytherapy using thermoplastic polyether ether ketone (PEEK) catheters in advanced cervical cancer MR-based brachytherapy, when MR-compatible applicators are not available.

Material and methods

Five cervical cancer patients received EBRT dose of 50 Gy in 25 fractions to whole pelvis using 3D conformal radiotherapy after standard pre-treatment evaluation. In our institute, interstitial brachytherapy (ISBT) is planned in BrachyVision TPS and routinely performed using stainless steel needles with Syed-Neblett template. Standard MR-compatible ISBT applicators were not available; therefore, the implant was carried out using PEEK catheters and Syed-Neblett template. The T1 and T2 MR and CT images of patients were acquired for treatment planning. Gross tumor volume (GTV), high-risk clinical target volume (HR-CTV), intermediate-risk clinical target volume (IR-CTV), and organs at risk (OARs) were delineated with the use of MR T2 weighted images, following GEC-ESTRO guidelines. Volumetric optimization was used for planning, and the treatment plan was executed with high-dose-rate (HDR) ¹⁹²Ir Gammamed Plus device.

Results

The dose prescribed to HR-CTV was 30 Gy low-dose-rate (LDR) equivalent (5 Gy × 4 fractions). Doses to target volume and OARs were analyzed using dose volume histogram (DVH). Dose values were biologically normalized to equivalent doses of 2 Gy fractions (EQD₂). The average tumor volume was 67 cc and the average D₉₀ of HR-CTV was 29 Gy (5.7 Gy/fraction) EQD₂. D₁₀₀ of HR-CTV volume was 18 Gy (3.8 Gy/fraction) EQD₂. The total doses of 2 cc of rectum and bladder were 70 Gy and 76 Gy EQD₂ (3.71 Gy and 4.04 Gy dose/fraction), respectively.

Conclusions

When the facilities for MR-compatible applicators are not available, MR-based ISBT is feasible with PEEK catheters using available resources for advanced cervical cancer. Doses to HR-CTV and IR-CTV were achieved, restricting doses to OARs as per GEC-ESTRO guidelines.