Clinical feasibility of interstitial brachytherapy using a "hybrid" applicator combining uterine tandem and interstitial metal needles based on CT for locally advanced cervical cancer

PURPOSE: To explore the dosimetric advantage of target volume and surrounding normal tissue by using interstitial (IS) brachytherapy (BT) based on three-dimensional CT in locally advanced cervical cancer, as a simple and effective clinical treatment approach. METHODS AND MATERIALS: Fifty-two patients with poor tumor response to external beam radiotherapy and a residual tumor >5 cm at the time of the first BT were included. IS BT was performed using a "hybrid" applicator combining uterine tandem and free metal needles based on three-dimensional CT. The high-risk clinical target volume (HR-CTV), intermediate-risI clinical target volume, and organs at risk were contoured. The total dose, including external beam radiotherapy (45 Gy in 25 fractions) and high-dose-rate BT (30 Gy in 5 fractions), was biologically normalized to conventional 2-Gy fractions. D-90 and D-100 for HR-CTV and intermediate-risk clinical target volume and D-2cc for the bladder, rectum, and sigmoid were analyzed. RESULTS: The mean D-90 value for HR-CTV was 88.4 +/- 3.5 Gy. Totally, 88.5% of the patients received D-90 for HR-CTV >= 87 Gy. The D-2cc for the bladder, rectum, and sigmoid were 81.1 +/- 5.6, 65.7 +/- 5.1, and 63.1 +/- 5.4 Gy, respectively. The mean number of needles was 6.9 +/- 1.3 for each application. IS BT was associated with minor complications. CONCLUSION: IS BT using the "hybrid" applicator provides a dosimetric advantage for target volume and organs at risk in large-volume (>5 cm) tumors and is, thereby, clinically feasible. However, the long-term curative effect and possible toxicity need further clinical observation. (C) 2016 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.