J.W.M. Mens

MR guided applicator reconstruction for brachytherapy of cervical cancer using the novel titanium Rotterdam applicator

A novel model of the titanium Rotterdam tandem and ovoid applicator is presented. As titanium produces artefacts in MR images, an MR sequence was sought and optimised for visualisation and accurate applicator reconstruction. The mean inter-observer (8 observers) variability for four patients was only 0.7 mm (maximum 1.7 mm).

What is the optimal number of library plans in ART for locally advanced cervical cancer

PURPOSE Library-of-plans ART is used to manage daily anatomy changes in locally advanced cervical cancer. In our institute, the library contains 2 VMAT plans for patients with large cervix-uterus motion. Increasing this number could be beneficial for tissue sparing, but is burdensome while the dosimetric gain is yet unclear. This studys aim is to determine the optimal number of plans at an individual patient level. MATERIAL AND METHODS Data of 14 treated patients were analyzed. Plan libraries were created containing 1-4 VMAT plans. Pre-treatment extent of uterus motion was defined by the 99th percentile of the Hausdorff distance (HD99). For dosimetric evaluations, OARs were contoured in daily CBCT scans, plan selection was simulated, and the V45Gy and V40Gy parameters were recorded. RESULTS Moderate to strong correlations were found between HD99 and the volume of spared OARs. All patients benefitted from adding a 2nd plan, as is the clinical practice. For patients with a HD99 between 30 and 50mm, a 3-plan library reduced the composite V40Gy with 11-21ml compared to a 2-plan library. CONCLUSION Patients with large uterus motion (HD99>30mm) would benefit from an extension of the plan library to 3. HD99 is an easy-to-implement criteria to select those patients pre-treatment.

Towards Automatic Plan Selection for Radiotherapy of Cervical Cancer by Fast Automatic Segmentation of Cone Beam CT Scans

We propose a method to automatically select a treatment plan for radiotherapy of cervical cancer using a Plan-of-the-Day procedure, in which multiple treatment plans are constructed prior to treatment. The method comprises a multi-atlas based segmentation algorithm that uses the selected treatment plan to choose between two atlas sets. This segmentation only requires two registration procedures and can therefore be used in clinical practice without using excessive computation time. Our method is validated on a dataset of 224 treatment fractions for 10 patients. In 37 cases (16%), no recommendation was made by the algorithm due to poor image quality or registration results. In 93% of the remaining cases a correct recommendation for a treatment plan was given.

Dynamics of patient reported quality of life and symptoms in the acute phase of online adaptive external beam radiation therapy for locally advanced cervical cancer

OBJECTIVE For locally advanced cervical cancer patients, treated with External Beam Radiotherapy (EBRT), Quality of Life (QoL) questionnaires arefrequently used to evaluate treatment-related symptoms and functioning scales. Currently, it is unknown how those evolve during the radiation treatment course. In this prospective study we report on weekly-captured patient-reported QoL and symptoms during image-guided adaptive radiotherapy (IGART) of cervical cancer patients. MATERIAL AND METHODS Between January 2012 and September 2016, all locally advanced cervical cancer patients treated with IGART and brachytherapy with or without chemotherapy or hyperthermia, were eligible. QoL was assessed at baseline; weekly during the first five weeks of treatment; 1week, 1 and 3months after treatment, using the EORTC QLQ-C30 and the QLQ-CX24 questionnaires. Comparisons were made with an age-matched norm population. RESULTS Among the 138 (70%) responders, most symptoms showed a moderate-to-large increase, reaching a maximum at the end of treatment, or first week after treatment with return to baseline value at 3months after treatment. While most symptoms gradually increased during the first five weeks, diarrhea and bowel cramps already markedly increased within the first three weeks to reach a plateau at the 5th week of treatment. Global health and functioning were temporarily decreased and returned to a plateau at baseline level 3months after treatment, except for cognitive functioning. CONCLUSION A profound impact on QoL was observed during the radiation treatment course, temporarily affecting functioning. The maximum impaired was reached at the end of EBRT.

OC-0546: Intra-fraction motion in Plan-of-the-Day IMRT for cervical cancer assessed by pre- and post-fraction CBCT scans

Purpose/Objective: In our institute, cervical cancer patients are treated with a library-based Plan-of-the-Day (PotD) protocol. In this protocol an in-room Cone Beam CT (CBCT) scan acquired just before dose delivery is used to select the treatment plan that is best fitting the observed anatomy. However, treatment accuracy may be compromised by shape and position changes of the cervix-uterus resulting from intra-fractional filling of the bladder and rectum, and by intra-fraction variations in patient setup. The purpose of this study is to quantify these uncertainties using preand postfraction acquired CBCT scans. Materials and Methods: Intra-fraction uncertainties were evaluated for 16 cervical cancer patients with a tip-of-uterus displacement larger than 2.5 cm as measured in an empty and full bladder planning CT scan. The treatment protocol includes a post-fraction CBCT to verify target coverage after dose delivery. In 316 preand post-fraction CBCT scans, the bladder, cervix-uterus, and rectum were delineated and volume changes in bladder and rectum filling were calculated. The preand post-fraction CBCT scans were aligned to the bony anatomy to quantify intra-fraction patient setup motion. To quantify intra-fraction displacements of the cervix-uterus, an in-house developed point-based non-rigid registration method was used to nonrigidly align the pre-fraction target shape to the post-fraction one (Fig. 1a). The intra-fraction distances were projected on the average cervix-uterus shape obtained by the non-rigid registration. Finally, intra-fraction cervix-uterus motion was correlated to volume differences in bladder. Results: The mean time between the preand post-fraction CBCT scans was 20.8±3.2 minutes (1SD). Bladder volume increased on average by 62±55 ml over all treatment fractions and rectum volume increased on average 4.6±32.8 ml. Table 1 summarizes the overall mean, systematic and random error for the intra-fraction patient setup motion, and the mean, SD, and 95 percentile for the intra-fraction cervix-uterus motion. Figure 1b shows for one patient a color representation of the treatment-averaged intra-fraction distances projected on the patient’s average cervix-uterus shape. The population-mean intra-fraction cervix-uterus displacements were 3.0±1.4, 4.7±2.8, and 3.4±2.1 mm projected on the LR, CC, and AP axis, respectively. There was a significant correlation between bladder inflow rate and cervix-uterus motion (R=0.6 and p<0.01).