Hybrid Image-Guided Brachytherapy for Locally Advanced Squamous Cell Carcinoma of the Cervix in Jose R. Reyes Memorial Medical Center: Introduction of the Technique in the Local Setting and Pilot Case Study

The aims of this pilot case study were to improve the dose coverage to the high-risk clinical target volume (HR-CTV) for locally advanced cervical cancer, to decrease dose received by the organs at risk, namely: rectum, bladder and sigmoid, and to evaluate the local control when using the combined intracavitary and interstitial image-guided brachytherapy (IGBT), also known as hybrid image-guided brachytherapy. Our patients with locally advanced cervical cancer, mostly with lateral extension to the parametria, posed challenges during brachytherapy as the tumor would receive insufficient dose when intracavitary brachytherapy is used alone. To address this limitation, better techniques such as hybrid image-guided brachytherapy was being explored in our institution. Our patient was diagnosed with Squamous Cell Carcinoma, Non-Keratinizing, Cervix, FIGO Stage IIIB. Patient underwent concurrent chemotherapy and conventional external beam radiotherapy to the pelvis. Image-guided brachytherapy was performed once a week during the 5th-8th week of treatment. With limited access to magnetic resonance imaging (MRI) prior to brachytherapy, transvaginal ultrasound was obtained to assist in the identification of HR-CTV. Prior to brachytherapy, repeat internal and rectovaginal exam revealed persistence of right parametrial extension. During brachytherapy, an intracavitary Fletcher Suit applicator was used together with 1 interstitial needle, which was inserted in the right parametria or at the 8 o’clock position from the cervix using freehand. After placement of the applicators, CT scan images of the pelvis were obtained which were then used for contouring of the HR-CTV and organs at risk, as well as for applicator reconstruction. CT-based treatment planning and optimization allowed for 3D dose-volume evaluation of the HR-CTV and organs at risk. Three treatment plans were generated for comparison, namely: conventional point A-based brachytherapy, intracavitary image-guided brachytherapy, and hybrid image-guided brachytherapy. Preliminary result of the local control was assessed during follow-up. For our patient’s case, the dose received by the HR-CTV D90 was increased from 73.67 Gy using the conventional point A-based brachytherapy to 79.28 Gy with the use of hybrid image-guided brachytherapy. The hybrid IGBT technique allowed for dose escalation to the HR-CTV while maintaining low doses to the organs at risk. Among the three treatment plans generated, the hybrid IGBT was able to achieve the lowest dose for the rectum 65.24 Gy, bladder 72.13 Gy and sigmoid 54.52 Gy. Intracavitary image-guided brachytherapy alone may achieve similar HR-CTV doses as with the hybrid IGBT but it could only be achieved with accompanying higher doses to the organs at risk. At 6 months follow-up, patient was noted with smooth cervix, free bilateral parametria and with no evidence of disease. Our pilot case study showed that hybrid image-guided brachytherapy for locally advanced cervical cancer may improve dose coverage to the HR-CTV, reduce dose to organs at risk and offer good local control of the disease. Further case series is recommended to improve on the application of the technique in the local setting and document treatment outcomes.Table 1Cumulative doses of HR-CTV, Rectum, Bladder and SigmoidConventional brachytherapyIntracavitary IGBTHybrid IGBTHR-CTV D9073.67 Gy78.88 Gy79.28 GyRectum D2cc67.76 Gy73.37 Gy65.24 GyBladder D2cc75.43 Gy78.7 Gy72.13 GySigmoid D2cc55 Gy54.89 Gy54.52 Gy Open table in a new tab