CT-guided interstitial brachytherapy for locally advanced cervical cancer: introduction of the technique and report of dosimetry

Objective To examine the dosimetric advantages of three-dimensional (3D) computed tomography (CT)-guided interstitial brachytherapy (BT) for target volume and surrounding normal tissue in patients with locally advanced cervical cancer, and to provide a simple and effective clinical treatment approach. Methods A total of 52 patients who had poor tumor response to external beam radiotherapy (EBRT) with a residual tumor greater than 5 cm at the time of BT were included. The patients were treated by 3D CT-guided interstitial BT using a "hybrid" applicator comprised of uterine tandem and free metal needles. The high-risk clinical target volume (HR-CTV), intermediate-risk clinical target volume (IR-CTV), and organs at risk (OAR) were contoured. The total dose, including external beam radiotherapy and high dose-rate BT, was biologically normalized to conventional 2 Gy fractions (EQD2). D90 and D100 for both HR-CTV and IR-CTV, and D2 cc for the bladder, rectum, and sigmoid were analyzed. Results The mean D90 value for HR-CTV was 88.4±3.5 Gy. The D2 cc for the bladder, rectum, and sigmoid were 81.1±5.6, 65.7±5.1, and 63.1±5.4 Gy, respectively.D2 cc ≤90 Gy for the bladder and D2 cc ≤70 Gy for the sigmoid were observed in all the patients.D2 cc ≤70 Gy for the rectum was observed in 89% of patients. Conclusions 3DCT-guided interstitial BT has a significant dosimetric advantage for target volume accompanied by few minor complications, and thereby may be clinically feasible for treating locally advanced cervical cancer. However, its long-term efficacy and possible toxicities will require further clinical observation. Key words: Cervical neoplasms/interstitial brachytherapy; Tomogranphy, X-ray computed, guide; Dosimetry