Dosimetric analysis and preliminary clinical result of image-guided brachytherapy with or without hybrid technique for cervical cancer using VariSource titanium ring applicator with “Siriraj Ring Cap”

Clinical Outcome Comparison between CT-Guided Versus all MRI-Guided Scenarios in Brachytherapy for Cervical Cancer: A Single-Institute Experience

OBJECTIVES

Image-guided adaptive brachytherapy (IGABT) is the standard of care for patients with cervical cancer. The objective of this study was to compare the treatment outcomes and adverse effects of computed tomography (CT)-guided and magnetic resonance imaging (MRI)-guided scenarios.

MATERIALS AND METHODS

Data of patients with cervical cancer treated using external beam radiotherapy followed by IGABT from 2012 to 2016 were retrospectively reviewed. CT-guided IGABT was compared with the three modes of MRI-guided IGABT: pre-brachytherapy (MRI Pre-BT) without applicator insertion for fusion, planning MRI with applicator in-place in at least 1 fraction (MRI ≥1Fx), and MRI in every fraction (MRI EveryFx). Patient characteristics, oncologic outcomes, and late radiation toxicity were analyzed using descriptive, survival, and correlation statistics.

RESULTS

Overall, 354 patients were evaluated with a median follow-up of 60 months. The 5-year overall survival (OS) rates were 61.5%, 65.2%, 54.4%, and 63.7% with CT-guided, MRI PreBT, MRI ≥1Fx, and MRI EveryFx IGABT, respectively with no significant differences (p = 0.522). The 5-year local control (LC) rates were 92.1%, 87.8%, 80.7%, and 76.5% (p = 0.133), respectively, with a significant difference observed between the CT-guided and MRI ≥1Fx (p = 0.018). The grade 3-4 late gastrointestinal toxicity rates were 6% in the CT-guided, MRI ≥1Fx, and MRI EveryFx, and 8% in MRI PreBT. The grade 3-4 late genitourinary toxicity rates were 4% in the CT-guided, 2% in MRI PreBT, 1% in MRI ≥1Fx, and none in MRI EveryFx. No significant differences were observed in the oncologic and toxicity outcomes among MRI PreBT, MRI ≥1Fx, and MRI EveryFx.

CONCLUSIONS

CT-guided IGABT yielded an acceptable 5-year OS, LC, and toxicity profile compared with all MRI scenarios and is a potentially feasible option in resource-limited settings.

Vaginal 11-point and volumetric dose related to late vaginal complications in patients with cervical cancer treated with external beam radiotherapy and image-guided adaptive brachytherapy

OBJECTIVE

To investigate the vaginal 11-point and volumetric dose-toxicity relationships in definitive cervical cancer radiotherapy.

METHODS

A retrospective cohort study of patients with cervical cancer with a complete response of at least 12 months was performed. Additional per vaginal examinations and patient-scoring questionnaires on the date of patient enrolment were assessed for vaginal strictures. Retrospective dosimetric analysis of vaginal 11-point and volumetric doses was performed with descriptive and probit analyses to investigate dose-toxicity relationships.

RESULTS

Ninety-seven patients were included in the study, with a 20-month median follow-up. The incidence rate of grade 3 vaginal strictures was 22.7%. A comparison between patients with grade 1-3 vaginal strictures revealed significant differences in age, stage, initial tumour size, and vaginal involvement. PIBS + 2, PIBS, PIBS-2, D + 5, and D2cc were all significantly different among grade 1-3 vaginal strictures and showed significant probit coefficients. The lateral dose points were significantly higher in grade 2 strictures, but negative probit coefficients failed to establish causal inferences. Post-estimation analyses yielded effective doses (ED) for 15% and 20% probability of grade 3 vaginal strictures (ED15 and ED20) for PIBS + 2 at 57.4 and 111 Gy₃, respectively. PIBS-2 yielded an ED20 of 7 Gy₃. D + 5 yielded positive ED10, ED15, and ED20 values of 52.2, 66.6, and 78 Gy₃, respectively.

CONCLUSIONS

This study showed a significant relationship between age, tumour size, and lower-third vaginal involvement with the incidence of vaginal toxicity. The goal of a cumulative radiotherapy dose of ≤ 55 Gy₃ to PIBS + 2, ≤5 Gy₃ to PIBS-2, and ≤ 65 Gy₃ to D + 5 points may reduce the risk of grade 3 vaginal stenosis to less than 15-20%.

Three-dimensional image-guided combined intracavitary and interstitial high-dose-rate brachytherapy in cervical cancer: A systematic review

PURPOSE

To evaluate the local control and toxicities of three-dimensional image-guided combined intracavitary and interstitial (IC/IS) high-dose-rate brachytherapy (BT) in cervical cancer through a systematic review.

METHODS AND MATERIALS

A systematic review of relevant studies was performed through the PubMed, Web of Science, and Cochrane Library databases through May 10, 2020. Articles reporting on IC/IS technology, volumetric doses to high-risk clinical target volume (HR-CTV) and organs at risk (OARs), tumor control and/or treatment-related side effects were identified. The key information, including the type of applicator, implantation technology, characteristics of implantation, volumetric doses, tumor control, and/or treatment-related side effects, was extracted. A probit model analysis between HR-CTV D90 and tumor local control was performed.

RESULTS

Twelve studies encompassing 520 patients were included in the probit model between HR-CTV D90 and the local control rate. The probit model showed a significant relationship between the HR-CTV D90 value and the local control probability, p = 0.003. The prescribed dose of 85 Gy_EQD2,10 would in theory warrant an 87.4% (95% confidence interval 82.5%-90.5%) local control rate.

CONCLUSION

IC/IS BT is an appropriate method to achieve a high therapeutic ratio for tumors with large volumes or poor responses after external irradiation in cervical cancer. The probit model showed that the dose escalation of HR-CTV D90 was helpful to improve the local tumor control rate.