Direction modulated brachytherapy (DMBT) for treatment of cervical cancer: A planning study with 192 Ir, 60 Co, and 169 Yb HDR sources

• Published in: Medical physics (Lancaster) 2017-12, Vol.44 (12), p.6538-6547
• Main Authors: Safigholi, Habib, Han, Dae Yup, Mashouf, Shahram, Soliman, Abraam, Meigooni, Ali S, Owrangi, Amir, Song, William Y
• Format: Article
• Language: English
• Subjects: Brachytherapy - adverse effects; Cobalt Radioisotopes - adverse effects; Cobalt Radioisotopes - therapeutic use; Female; Humans; Iridium Radioisotopes - adverse effects; Iridium Radioisotopes - therapeutic use; Monte Carlo Method; Organs at Risk - radiation effects; Radioisotopes - adverse effects; Radioisotopes - therapeutic use; Radiotherapy Planning, Computer-Assisted - methods; Uterine Cervical Neoplasms - radiotherapy; Ytterbium - adverse effects; Ytterbium - therapeutic use
• ISSN: 0094-2405; 2473-4209
• DOI: 10.1002/mp.12598

To evaluate plan quality of a novel MRI-compatible direction modulated brachytherapy (DMBT) tandem applicator using Ir, Co, and Yb HDR brachytherapy sources, for various cervical cancer high-risk clinical target volumes (CTV ). The novel DMBT tandem applicator has six peripheral grooves of 1.3-mm diameter along a 5.4-mm thick nonmagnetic tungsten alloy rod. Monte Carlo (MC) simulations were used to benchmark the dosimetric parameters of the Ir, Co, and Yb HDR sources in a water phantom against the literature data. 45 clinical cases that were treated using conventional tandem-and-ring applicators with Ir source ( Ir-T&R) were selected consecutively from intErnational MRI-guided BRAchytherapy in CErvical cancer (EMBRACE) trial. Then, for each clinical case, 3D dose distribution of each source inside the DMBT and conventional applicators were calculated and imported onto an in-house developed inverse planning optimization code to generate optimal plans. All plans generated by the DMBT tandem-and-ring (DMBT T&R) from all three sources were compared to the respective Ir-T&R plans. For consistency, all plans were normalized to the same CTV D90 achieved in clinical plans. The D for organs at risk (OAR) such as bladder, rectum, and sigmoid, and D90, D98, D10, V100, and V200 for CTV were calculated. In general, plan quality significantly improved when a conventional tandem (Con.T) is replaced with the DMBT tandem. The target coverage metrics were similar across Ir-T&R and DMBT T&R plans with all three sources (P > 0.093). Co-DMBT T&R generated greater hot spots and less dose homogeneity in the target volumes compared with the Ir- and Yb-DMBT T&R plans. Mean OAR doses in the DMBT T&R plans were significantly smaller (P