The radiobiological impact of motion tracking of liver, pancreas and kidney SBRT tumors in a MR-linac

The purpose of this work is to evaluate and quantify the potential radiobiological advantages of tumor tracking using the MR-linac for three disease sites: liver, pancreas and kidney. From each disease site, three patients were selected and 4DCT data sets were used. We applied two planning methods using the Monaco treatment planning system (Elekta AB,Stockholm,Sweden): (1) the conventional ITV method using a 6MV Agility beam and (2) a simulated tracking method using MLC GTV tracking with a 7MV MR-linac beam model incorporating a 1.5 T transverse magnetic field. A 5 mm isotropic PTV margin was added to the ITV or the GTV, and 95% of the PTV volume received 100% of the prescription dose. To evaluate the potential radiobiological advantages of tumor tracking, the normal tissue complication probabilities (NTCPs) were calculated for each organ at risk (OAR) using the Layman Kutcher Burman (LKB) model. The average reduction in the target volume, due to tracking, was 31.1%, 26.3% and 26.9% for liver, pancreas and kidney patients, respectively. For each OAR, the % differences in NTCP between the two methods were calculated. The mean 2 Gy equivalent OAR dose for all patients was less than 29.1 Gy, below which the NTCP for most OARs was not sensitive to equivalent uniform dose (EUD). As a result, a NTCP benefit, due to tracking, was observed in 26% of the data. For all three disease sites, the maximum NTCP improvements were for the normal kidney, the bowels, and the duodenum, with reductions in associated toxicities of 79% (radiation nephropathy), 69% (stricture/fistula) and 25% (ulceration), respectively. This study demonstrates the potential benefit of using a MR-linac tracking system to reduce NTCPs. The normal kidney, the bowels and the duodenum showed the largest NTCP improvements. This, in part, is due to the rapid changes in NTCP for small EUD changes.

Phase 1-2 Study of Stereotactic Ablative Radiotherapy Including Regional Lymph Node Irradiation in Patients With High-Risk Prostate Cancer (SATURN): Early Toxicity and Quality of Life

PURPOSE

Five-fraction stereotactic ablative radiation therapy appears to be gaining popularity in treatment of prostate cancer, but it has not been extensively tested in the context of pelvic radiation. The objective of this prospective prostate and pelvic SABR study is to report the acute toxicity, late toxicity, and quality of life (QoL) after study completion.

METHODS AND MATERIALS

A phase 1/2 study was conducted for patients with high-risk prostate cancer. Radiation therapy was planned to deliver 25 Gy to pelvis and seminal vesicles (SV) and a simultaneous integrated boost (SIB) of up to 40 Gy to the prostate in 5 fractions, weekly, over 29 days. Androgen deprivation therapy was used for 12 to 18 months. Common Terminology Criteria for Adverse Events version 3.0 was used to assess worst acute and late toxicities. QoL data was captured using the Expanded Prostate Cancer Index Composite questionnaire (EPIC).

RESULTS

Thirty patients completed the planned treatment with a median follow-up of 25.7 months (range, 18.5-30.7 months). The following "worst" acute and late toxicities were observed: grade 2 genitourinary toxicity, 46.7% and 52%, respectively; grade 2 gastrointestinal toxicity, 3.3% and 32%, respectively. No grade 3 or higher toxicities were noted. Mean (95% confidence interval) EPIC urinary QoL scores were 86.6 (81.9-91.3), 87.1 (81.4-92.6), and 87.9 (80.1-95.7) at baseline, 3 months and 24 months; bowel scores were 94.1 (91.3-97.0), 93.2 (89.1-97.2), and 92.4 (87.7- 97.1), respectively.

CONCLUSIONS

This gantry-based novel fractionation schedule incorporating pelvic radiation for high-risk prostate cancer in combination with androgen deprivation therapy is feasible and well tolerated.

Developing and Evaluating Multimedia Patient Education Tools to Better Prepare Prostate-Cancer Patients for Radiotherapy Treatment (Randomized Study)

The purpose of this study is to determine the effectiveness of multimedia educational tools to improve CT planning preparation for intensity modulated radiotherapy (IMRT) for prostate cancer. Many patients are not prepared when given verbal preparation instructions to have a full bladder and empty rectum for their IMRT and require being rescanned, which results in additional costs for the patient and the hospital. A pamphlet and video outlining the proper preparation for prostate IMRT was created to decrease additional scans and the associated costs, while increasing patient satisfaction. A controlled, randomized experimental group study was conducted to examine the effectiveness of the multimedia tools (the video and the pamphlet), as compared to the pamphlet only, in preparing patients for their planning CT appointment. We found no statistical difference between the multimedia group and the pamphlet group in patients' preparedness for their appointments and the rescanning rate. However, patients in the multimedia group indicated that they felt more prepared about their treatment after watching the video and stated that they would recommend the video to other patients with prostate cancer. Furthermore, patients who had to wait longer for their planning CT appointment felt less prepared by the materials than those with a shorter wait time. We recommend reducing wait times between appointments as much as possible to increase patients' preparedness for the planning CT. We conclude that providing multimedia treatment information and minimizing wait times increases patients' feelings of preparedness leading to a more positive treatment experience and reducing costly rescans.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02410291.

Local control and fracture risk following stereotactic body radiation therapy for non-spine bone metastases

AIMS

To report local control and toxicity rates for patients treated with stereotactic body radiotherapy (SBRT) for non-spine bone metastases.

METHODS AND MATERIALS

Eighty-one patients with 106 non-spine bone metastases were treated between 2011 and 2014 and retrospectively reviewed. Indications included: oligometastases (63%), oligoprogression (17.3%), retreatment (2.4%) or other (17.3%). Cumulative incidence function was used to assess local recurrence and fracture probability. Bivariate relationships were investigated based on selected patient, tumour and dose-volume factors.

RESULTS

Mean follow-up was 13 months (range, 0.25-45.6) and the median patient age was 66.4 years (range, 36-86). Most patients were male (60.5%) and the predominant histology prostate cancer (32%). Bone metastases were most commonly located in the pelvis (41.5%) and almost half sclerotic. The most common prescriptions were 30 Gy/5 (30.2%) and 35 Gy/5 (42.5%). The cumulative incidence of local recurrence at 6,18 and 24 months respectively was 4.7%, 8.3% and 13.3% with a mean time to local recurrence of 11.8 months (range, 3.9-23.4). A significant association was found between local recurrence and volume of the PTV (p = 0.02), with larger PTVs having a greater risk of local failure. Fracture was observed radiographically in the treatment volume in 9/106 (8.5%) of treated lesions and the mean time to fracture was 8.4 months (range, 0.7-32.5 months). With respect to predictors, a trend was observed for lytic lesions (p = 0.11) and female gender (p = 0.09).

CONCLUSIONS

The results of this study confirm that SBRT yields high rates of long-term local control for non-spine bone metastases with a low fracture risk.

Once-weekly versus every-other-day stereotactic body radiotherapy in patients with prostate cancer (PATRIOT): A phase 2 randomized trial

BACKGROUND AND PURPOSE

Prostate stereotactic body radiotherapy (SBRT) regimens differ in time, dose, and fractionation. We completed a multicentre, randomized phase II study to investigate the impact of overall treatment time on quality of life (QOL).

MATERIAL AND METHODS

Men with low and intermediate-risk prostate cancer were randomly assigned to 40 Gy in 5 fractions delivered once per week (QW) vs. every other day (EOD). QOL was assessed using the Expanded Prostate Cancer Index Composite. The primary endpoint was the proportion with a minimum clinically important change (MCIC) in bowel QOL during the acute (≤12 week) period, and analysis was by intention-to-treat. ClinicalTrials.gov NCT01423474.

RESULTS

152 men from 3 centres were randomized with median follow-up of 47 months. Patients treated QW had superior acute bowel QOL with 47/69 (68%) reporting a MCIC compared to 63/70 (90%) treated EOD (p = 0.002). Fewer patients treated QW reported moderate-severe problems with bowel QOL during the acute period compared with EOD (14/70 [20%] vs. 40/70 [57%], p < 0.001). Acute urinary QOL was also better in the QW arm, with 52/67 (78%) vs 65/69 (94%) experiencing a MCIC (p = 0.006). There were no significant differences in late urinary or bowel QOL at 2 years or last follow-up.

CONCLUSION

Prostate SBRT delivered QW improved acute bowel and urinary QOL compared to EOD. Patients should be counselled regarding the potential for reduced short-term toxicity and improved QOL with QW prostate SBRT.

Abstract P5-07-03: Withdrawn

This abstract was withdrawn by the authors.

Perfusion imaging of colorectal liver metastases treated with bevacizumab and stereotactic body radiotherapy

Stereotactic body radiotherapy (SBRT) and bevacizumab are used in the treatment of colorectal liver metastases. This study prospectively evaluated changes in perfusion of liver metastases in seven patients treated with both bevacizumab and SBRT. Functional imaging using dynamic contrast-enhanced CT perfusion and contrast-enhanced ultrasound were performed at baseline, after bevacizumab, and after SBRT. After bevacizumab, a significant decrease was found in permeability (−28%, p < .05) and blood volume (−47%, p < .05), while SBRT led to a significant reduction in permeability (−22%, p < .05) and blood flow (−37%, p < .05). This study demonstrates that changes in perfusion can be detected after bevacizumab and SBRT.

Pooled analysis of stereotactic ablative radiotherapy for primary renal cell carcinoma: A report from the International Radiosurgery Oncology Consortium for Kidney (IROCK)

BACKGROUND

Stereotactic ablative radiotherapy (SABR) is an emerging therapy for primary renal cell carcinoma. The authors assessed safety, efficacy, and survival in a multi-institutional setting. Outcomes between single-fraction and multifraction SABR were compared.

METHODS

Individual patient data sets from 9 International Radiosurgery Oncology Consortium for Kidney institutions across Germany, Australia, the United States, Canada, and Japan were pooled. Toxicities were recorded using Common Terminology Criteria for Adverse Events, version 4.0. Patient, tumor, and treatment characteristics were stratified according to the number of radiotherapy fractions (single vs multiple). Survival outcomes were examined using Kaplan-Meier estimates and Cox proportional-hazards regression.

RESULTS

Of 223 patients, 118 received single-fraction SABR, and 105 received multifraction SABR. The mean patient age was 72 years, and 69.5% of patients were men. There were 83 patients with grade 1 and 2 toxicity (35.6%) and 3 with grade 3 and 4 toxicities (1.3%). The rates of local control, cancer-specific survival, and progression-free survival were 97.8%, 95.7%, and 77.4%, respectively, at 2 years; and they were 97.8%, 91.9%, and 65.4%, respectively, at 4 years. On multivariable analysis, tumors with a larger maximum dimension and the receipt of multifraction SABR were associated with poorer progression-free survival (hazard ratio, 1.16 [P < .01] and 1.13 [P = .02], respectively) and poorer cancer-specific survival (hazard ratio, 1.28 [P < .01] and 1.33 [P = .01], respectively). There were no differences in local failure between the single-fraction cohort (n = 1) and the multifraction cohort (n = 2; P = .60). The mean ( ± standard deviation) estimated glomerular filtration rate at baseline was 59.9 ± 21.9 mL per minute, and it decreased by 5.5 ± 13.3 mL per minute (P < .01).

CONCLUSIONS

SABR is well tolerated and locally effective for treating patients who have primary renal cell carcinoma and has an acceptable impact on renal function. An interesting observation is that patients who receive single-fraction SABR appear to be less likely to progress distantly or to die of cancer. Cancer 2018;124:934-42. © 2017 American Cancer Society.

The effect of prone and supine treatment positions for the pre-operative treatment of rectal cancer on organ-at-risk sparing and setup reproducibility using volumetric modulated arc therapy

Background and purpose

To compare organ-at-risk doses and setup reproducibility using the prone and supine orientations in volumetric modulated arc therapy (VMAT) for rectal cancer.

Materials and methods

Seventeen consecutive rectal cancer patients undergoing preoperative radiation were selected and setup in either the prone (N = 8) or supine (N = 9) position. All patients were treated using posteriorly-applied VMAT. Bladder and small bowel dose and cone beam CT (CBCT) reproducibility metrics were retrospectively collected.

Results

Dose metrics for bladder and small bowel did not show significant differences between the prone and supine orientations. The prone data had a trend for smaller irradiated volumes than supine for the small bowel at lower doses—V20 (prone: 135 ± 99 cm³; supine: 201 ± 162 cm³) and V30 (prone: 78 ± 71 cm³; supine: 105 ± 106 cm³). At higher doses, the trend reversed as exemplified by the small bowel V50.4 (prone: 20 ± 28 cm³; supine: 10 ± 14 cm³). CBCT data showed that rotational errors in pitch and roll were significantly larger for the prone vs. supine orientation (pitch: 2.0° ± 1.3° vs. 0.8° ± 1.1° p < 0.001; roll: 1.0° ± 0.9° vs. 0.3° ± 0.5°, p < 0.001).

Conclusions

Bladder and small bowel doses were not significantly different when comparing VMAT plans developed for the prone and supine orientations. The supine orientation demonstrated improved setup reproducibility.

Robotic Total Pelvic Exenteration: Video-Illustrated Technique

BACKGROUND

Robotic-assisted total pelvic exenteration (TPE) can offer a minimally invasive approach to a major multi-organ operation.

METHODS

In this video, we summarize a stepwise approach to robotic TPE in a 70 year-old female Jehovah's witness with a history of cervical cancer post-chemoradiation and radical hysterectomy who experienced local recurrence at the vaginal cuff involving the rectum and bladder.

RESULTS

The patient was placed in the lithotomy position. A total of six robotic ports were used and the da Vinci Si robotic system was docked between the legs. We proceeded as follows: (1) the abdomen and pelvis were thoroughly explored for evidence of metastatic disease; (2) the pelvic sidewalls were mobilized and bilateral ureters identified; (3) the mesorectal plane was dissected to the level of the levators; (4) the lateral and anterior pelvic structures were completely mobilized, and parametrial tissues were mobilized to the pelvic wall; (5) the bladder was separated from the pubis symphysis, the space of Retzius entered, and the bladder and proximal urethra freed; (6) a perineal incision was made around the vagina, perineal body, and anus, which were excised; (7) an Alloderm mesh secured the pelvic floor, and an omental J flap was mobilized; and (8) a 6 cm incision was utilized for creation of an ileal conduit and a permanent-end colostomy. Final pathology was consistent with recurrent cervical squamous cell carcinoma invading into the vaginal, bladder, and rectal walls. Surgical margins and seven lymph nodes were negative for carcinoma.

CONCLUSION

Robotic-assisted TPE is technically feasible in a Jehovah's witness under a multidisciplinary surgical team, even in the setting of prior radical hysterectomy and irradiated tissue.