Development and Feasibility of a Patient-Derived Training Simulator for Image-Guided Adaptive Brachytherapy of Locally Advanced Cervical Cancers

Background Image-guided adaptive brachytherapy (IGABT) plays a pivotal role in definitive radiotherapy of cervical cancer. Although the combination of a tandem and ovoid applicator with interstitial needles (IC/IS brachytherapy) is an efficient IGABT technique for bulky irregular-shaped tumors, training opportunities for IC/IS brachytherapy remain limited. Thus, we developed a training simulator for IC/IS brachytherapy for locally advanced cervical cancer and tested its feasibility. Methods The training simulator combined a patient-derived soft silicone tumor phantom with an acrylic tube mimicking the vagina. The tumor phantom was modeled on a cervical cancer patient treated with IGABT at our institute between 2012–2020, through detailed inspection of their three-dimensional (3D) high-risk clinical target volume (HR-CTV) at the first brachytherapy session. A true-scale tumor phantom was created from the HR-CTV data using 3D-printing. The feasibility of the training simulator was investigated by comparing treatment plans between the following six sessions (sessions #1–#3, with a Fletcher-Suit Asian Pacific applicator; #4–#6, with a Venezia applicator): in sessions #1 and #4, an expert inserted a tandem and ovoids (T&O); in sessions #2 and #5, a resident inserted a T&O plus four needles; and in sessions #3 and #6, an expert inserted a T&O plus four needles. At each session, the highest possible dose was prescribed to the HR-CTV while keeping the D2cc of the rectum and bladder (derived from the model case) below 6 and 7.6 Gy, respectively. Results The training simulator was developed using the HR-CTV data of a FIGO stage IIIB tumor (68 ⋅ 49 ⋅ 45 mm) selected from one of 495 candidates. The feasibility tests with a Fletcher-Suit Asian Pacific applicator resulted in HR-CTV D90 of 4.23, 5.69, and 6.70 Gy for sessions #1, #2, and #3, respectively. With a Venezia applicator, HR-CTV D90 was 4.16, 6.20, and 6.45 Gy for sessions #4, #5, and #6, respectively. Conclusions The tumor phantom was a good representation that resulted in various HR-CTV D90 doses depending on the physician’s experience and applicator type. Further evaluation of the training simulator is warranted to confirm its educational value for IC/IS brachytherapy for locally advanced cervical cancer.