Lotte J. Lutkenhaus

Evaluation of delivered dose for a clinical daily adaptive plan selection strategy for bladder cancer radiotherapy

PURPOSE To account for variable bladder size during bladder cancer radiotherapy, a daily plan selection strategy was implemented. The aim of this study was to calculate the actually delivered dose using an adaptive strategy, compared to a non-adaptive approach. MATERIAL AND METHODS Ten patients were treated to the bladder and lymph nodes with an adaptive full bladder strategy. Interpolated delineations of bladder and tumor on a full and empty bladder CT scan resulted in five PTVs for which VMAT plans were created. Daily cone beam CT (CBCT) scans were used for plan selection. Bowel, rectum and target volumes were delineated on these CBCTs, and delivered dose for these was calculated using both the adaptive plan, and a non-adaptive plan. RESULTS Target coverage for lymph nodes improved using an adaptive strategy. The full bladder strategy spared the healthy part of the bladder from a high dose. Average bowel cavity V30Gy and V40Gy significantly reduced with 60 and 69ml, respectively (p<0.01). Other parameters for bowel and rectum remained unchanged. CONCLUSIONS Daily plan selection compared to a non-adaptive strategy yielded similar bladder coverage and improved coverage for lymph nodes, with a significant reduction in bowel cavity V30Gy and V40Gy only, while other sparing was limited.

Reduction in cardiac volume during chemoradiotherapy for patients with esophageal cancer

We investigated the change in cardiac volume over the course of chemoradiotherapy in 26 patients treated for esophageal cancer, using cone beam CT imaging. The cardiac volume reduced significantly, with a median reduction of 8%. A significant relationship with planned cardiac dose was not found.

Potential dosimetric benefit of an adaptive plan selection strategy for short-course radiotherapy in rectal cancer patients

PURPOSE An adaptive plan selection strategy can account for daily target volume variations for radiotherapy in rectal cancer patients. The aim was to quantify the daily dosimetric consequences of plan selection compared to a non-adaptive approach. MATERIALS AND METHODS Ten patients with rectal cancer, treated with 25Gy in five fractions to the mesorectum and pelvic lymph nodes, were selected. The adaptive strategy was simulated by creating three plans per patient, with varying upper ventral PTV margins, and selecting the smallest PTV covering the entire mesorectum on every daily CBCT scan. Subsequently, mesorectum, bladder, and bowel cavity were delineated on these scans. Daily dose-volume histograms were calculated for both the adaptive and non-adaptive plan, with a ventral PTV margin of 20mm. Coverage of the mesorectum, defined as V95%>99%, was calculated, as well as bladder and bowel cavity V95% and V15Gy. RESULTS In one patient, mesorectum coverage improved. A reduction in bladder V95% and bowel cavity V15Gy was found, of 6.9% and 18.4cm(3) (p<0.01), respectively. CONCLUSION Plan selection for radiotherapy in rectal cancer can improve coverage of the target volume. Overall dosimetric sparing of bladder and bowel cavity was limited but could be beneficial for individual patients.

Reduction of heart volume during neoadjuvant chemoradiation in patients with resectable esophageal cancer

BACKGROUND AND PURPOSE Neoadjuvant chemoradiation (nCRT) followed by surgery is considered curative intent treatment for patients with resectable esophageal cancer. The aim was to establish hemodynamic aspects of changes in heart volume and to explore whether changes in heart volume resulted in clinically relevant changes in the dose distribution of radiotherapy. METHODS A prospective study was conducted in patients who were treated with nCRT consisting of carboplatin and paclitaxel concomitant with radiotherapy (41.4 Gy/1.8 Gy per fraction). Physical parameters, cardiac volume on CT and Cone beam CT, cardiac blood markers and cardiac ultrasound were obtained. RESULTS In 23 patients a significant decrease of 55.3 ml in heart volume was detected (95% CI 36.7-73.8 ml, p<0.001). There was a decrease in both systolic (mean decrease 18 mmHg, 95% CI 11-26 mmHg, p<0.001) and diastolic blood pressure (mean decrease 8 mmHg, 95% CI 2-14 mmHg, p=0.008) and an increase in heart rate with 6 beats/min (95% CI 1-11 beats/min, p=0.021). Except for Troponin T, no change in other cardiac markers and echocardiography parameters were observed. The change in heart volume did not result in a clinically relevant change in radiation dose distribution. CONCLUSION Heart volume was significantly reduced, but was not accompanied by overt cardiac dysfunction. All observed changes in hemodynamic parameters are consistent with volume depletion. Adaptation of the treatment plan during the course of radiotherapy is not advocated.

Plan selection strategy for rectum cancer patients: An interobserver study to assess clinical feasibility

BACKGROUND AND PURPOSE In radiotherapy for rectum cancer, the target volume is highly deformable. An adaptive plan selection strategy can mitigate the effect of these variations. The purpose of this study was to evaluate the feasibility of an adaptive strategy by assessing the interobserver variation in CBCT-based plan selection. MATERIAL AND METHODS Eleven patients with rectum cancer, treated with a non-adaptive strategy, were selected. Five CBCT scans were available per patient. To simulate the plan selection strategy, per patient three PTVs were created by varying the anterior upper mesorectum margin. For each CBCT scan, twenty observers selected the smallest PTV that encompassed the target volume. After this initial baseline measurement, the gold standard was determined during a consensus meeting, followed by a second measurement one month later. Differences between both measurements were assessed using the Wilcoxon signed-rank test. RESULTS In the baseline measurement, the concordance with the gold standard was 69% (range: 60-82%), which improved to 75% (range: 60-87%) in the second measurement (p=0.01). For the second measurement, 10% of plan selections were smaller than the gold standard. CONCLUSION With a plan selection consistency between observers of 75%, a plan selection strategy for rectum cancer patients is feasible.

PO-0759: Results of radical radiotherapy with a tumour boost for bladder cancer in patients unfit for surgery

Material and Methods: Between January 2002 and December 2003, data of 440 pts (mean age: 65 years, range 42-81) treated with radical prostatectomy (RP) were collected by 14 Italian RT Departments. Of the 411 pts available for the 10 year analysis (median follow up: 111 months), 284 (69.1%) received PORT (started <6 months after RP) and 127 underwent SART because of increasing PSA level after having been undetectable or persistently elevated PSA (> 6 months after RP). Gleason Score (GS) > 7 and positive surgical margins (SM+) have been shown by 69% pts and 74.5% respectively; 76.5% presented locally advanced disease (pT34), 27 (6.7%) positive pelvic nodes; 163 pts (40.2%) revealed seminal vesicles invasion (SVI). All pts received RT to the prostatic fossa (mean dose of 67.8 Gy, range: 60-76). Pelvic RT was delivered to 111 pts (27%). Androgen deprivation (AD) was prescribed to 47,3% pts. Among 127 SART pts, pre-RT PSA level was 1 ng/mL or less in 56 pts (44,1%).

Regarding Edmunds et al. Cardiac volume effects during chemoradiotherapy for esophageal cancer.

http://dx.doi.org/10.1016/j.radonc.2014.12.008 0167-8140/ 2014 Elsevier Ireland Ltd. All rights reserved. To the Editor We would like to thank Edmunds et al. for their interest in our article on cardiac reduction for patients receiving chemoradiotherapy for esophageal cancer [1]. Their reported median cardiac volume reduction of 3.3% over the course of chemoradiotherapy confirms our results. We consider their finding regarding the reverting of the cardiac volume to the baseline level after three months particularly interesting. This indicates that the clinical implications of the volume reduction are limited. A dose–effect relationship was not found in both patient cohorts. Edmunds et al. do not report the actual values for the heart dose parameters in their population. Since eight of their patients were treated with volumetric modulated arc therapy (VMAT), cardiac doses will most likely be lower than those reported in our study, in which patients were treated with a conformal four-field technique. However, it is currently still unknown whether a threshold dose exists for which the cardiac volume reduction occurs. In their letter, Edmunds et al. conclude that adaptive planning is not recommended based on the observations that cardiac dose is not a predictor for cardiac reduction, and that the reduction does not appear to be permanent. However, whether or not adaptive radiotherapy should be considered, is depending on dosimetric changes during the course of radiotherapy. These changes could result in inaccurate dose delivery to the tumor and organs at risk. Dosimetric changes could be induced by this reduction in cardiac volume, but this has not been investigated. Therefore, based on the presented data, no recommendations can be made regarding the need for adaptive radiotherapy.