The impact of varying rectal contours on rectal dose in prostate cancer patients treated with hypofractionated radiation

15598 Background: In curative radiation treatment of prostate cancer,the advent of 3DCRT has made a reduction in the incidence of normal tissue toxicities while optimizing tumor control. To optimize 3DCRT, the ICRU has published standard definitions of target volumes and organs at risk such that the tumor can receive the optimal dose with as little as possible dose to the organs at risk. However, the definition of the rectum as an organ at risk in radiation treatment of the prostate varies widely among institutions and so does the report of toxicities. We studied the effect of varying rectal contouring on rectal dose obtained from DVHs in a homogenous group of prostate cancer patients treated with hypo fractionationed radiation. Methods: 71 patients with favorable risk prostate cancer treated with a total of 66Gy in 3Gy/day fractionation.18 MV photons in a 5-field technique was used. None of the patients received hormonal therapy. Their treatment plans were archived and the rectum was re-contoured by a single investigator. 4 different contours were drawn to compare the rectal dose: i) the whole rectum from the anal verge to the recto sigmoid junction (WR); ii) the rectum from 1cm below the PTV to 1cm above (RPTV); iii) the rectal wall (i.e. the inner and outer rectal wall) from the anal verge to the recto sigmoid junction (RW); iv) the rectal wall from 1cm below the PTV to 1cm above (RWPTV) Results: There were significant differences in the median volume, minimum, mean rectal doses and dose to 50% of the volume, (p=0.0001). The whole rectum (WR) is having the lowest and the rectal wall with 1cm above and below the PTV (RWPTV) having the highest in all the parameters. The only parameter not significantly different among the 4 contours is the maximum rectal dose. Conclusion: the varied rectal contouring across different institutions is a possible reason for the broadly different reports of rectal toxicity after prostate irradiation. Our results suggest significant differences in rectal doses with varied contouring. Contouring the rectal wall only and limiting the volume to 1cm above and below the PTV confers the highest mean rectal dose. Comparison of rectal toxicity between institutions can only be meaningful if a consensual volume definition of the organ at risk is agreed upon. No significant financial relationships to disclose.

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Influence of Organ at Risk Definition on Rectal Dose-Volume Histograms in Patients with Prostate Cancer Undergoing External-Beam Radiotherapy

Strahlentherapie und Onkologie ◽

10.1007/s00066-006-1462-7 ◽

2006 ◽

Vol 182 (5) ◽

pp. 277-282 ◽

Cited By ~ 17

Author(s):

Dirk Boehmer ◽

David Kuczer ◽

Harun Badakhshi ◽

Simone Stiefel ◽

Wolf Kuschke ◽

...

Keyword(s):

Prostate Cancer ◽

At Risk ◽

External Beam Radiotherapy ◽

External Beam ◽

Dose Volume Histograms ◽

Rectal Dose ◽

Dose Volume ◽

Risk Definition ◽

Organ At Risk

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Interfraction Anatomical Variability Can Lead to Significantly Increased Rectal Dose for Patients Undergoing Stereotactic Body Radiotherapy for Prostate Cancer

Technology in Cancer Research & Treatment ◽

10.1177/1533034616649495 ◽

2016 ◽

Vol 16 (2) ◽

pp. 178-187 ◽

Cited By ~ 9

Author(s):

Michael Wahl ◽

Martina Descovich ◽

Erin Shugard ◽

Dilini Pinnaduwage ◽

Atchar Sudhyadhom ◽

...

Keyword(s):

Prostate Cancer ◽

Computed Tomography ◽

At Risk ◽

Stereotactic Body Radiotherapy ◽

Organs At Risk ◽

Anatomical Variation ◽

High Dose ◽

Megavoltage Computed Tomography ◽

Organ At Risk ◽

The Impact

Stereotactic body radiotherapy for prostate cancer is rapidly growing in popularity. Stereotactic body radiotherapy plans mimic those of high-dose rate brachytherapy, with tight margins and inhomogeneous dose distributions. The impact of interfraction anatomical changes on the dose received by organs at risk under these conditions has not been well documented. To estimate anatomical variation during stereotactic body radiotherapy, 10 patients were identified who received a prostate boost using robotic stereotactic body radiotherapy after completing 25 fractions of pelvic radiotherapy with daily megavoltage computed tomography. Rectal and bladder volumes were delineated on each megavoltage computed tomography, and the stereotactic body radiotherapy boost plan was registered to each megavoltage computed tomography image using a point-based rigid registration with 3 fiducial markers placed in the prostate. The volume of rectum and bladder receiving 75% of the prescription dose (V75%) was measured for each megavoltage computed tomography. The rectal V75% from the daily megavoltage computed tomographies was significantly greater than the planned V75% (median increase of 0.93 cm3, P < .001), whereas the bladder V75% on megavoltage computed tomography was not significantly changed (median decrease of −0.12 cm3, P = .57). Although daily prostate rotation was significantly correlated with bladder V75% (Spearman ρ = .21, P = .023), there was no association between rotation and rectal V75% or between prostate deformation and either rectal or bladder V75%. Planning organ-at-risk volume-based replanning techniques using either a 6-mm isotropic expansion of the plan rectal contour or a 1-cm expansion from the planning target volume in the superior and posterior directions demonstrated significantly improved rectal V75% on daily megavoltage computed tomographies compared to the original stereotactic body radiotherapy plan, without compromising plan quality. Thus, despite tight margins and full translational and rotational corrections provided by robotic stereotactic body radiotherapy, we find that interfraction anatomical variations can lead to a substantial increase in delivered rectal doses during prostate stereotactic body radiotherapy. A planning organ-at-risk volume-based approach to treatment planning may help mitigate the impact of daily organ motion and reduce the risk of rectal toxicity.

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Dosimetry for Organs at Risk With and Without Use of Perirectal Hydrogel Spacer in Prostate Cancer Patients Treated With SBRT

International Journal of Radiation Oncology*Biology*Physics ◽

10.1016/j.ijrobp.2017.06.1161 ◽

2017 ◽

Vol 99 (2) ◽

pp. E233

Author(s):

D.B. Fried ◽

R.S. DuBose ◽

K. Johnson ◽

M. Cogdell ◽

J.A. Gersh ◽

...

Keyword(s):

Prostate Cancer ◽

At Risk ◽

Cancer Patients ◽

Organs At Risk

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212 poster workshop Predictive value of mean rectal dose for acute rectal toxicity in patients with prostate cancer treated with definitive conformal radiotherapy: preliminary results from a prospective multi-center study

Radiotherapy and Oncology ◽

10.1016/s0167-8140(04)82079-6 ◽

2004 ◽

Vol 73 ◽

pp. S96 ◽

Cited By ~ 1

Keyword(s):

Prostate Cancer ◽

Predictive Value ◽

Conformal Radiotherapy ◽

Rectal Toxicity ◽

Preliminary Results ◽

Rectal Dose ◽

Multi Center Study ◽

Center Study

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Clinically Applicable Segmentation of Head and Neck Anatomy for Radiotherapy: Deep Learning Algorithm Development and Validation Study

Journal of Medical Internet Research ◽

10.2196/26151 ◽

2021 ◽

Vol 23 (7) ◽

pp. e26151

Author(s):

Stanislav Nikolov ◽

Sam Blackwell ◽

Alexei Zverovitch ◽

Ruheena Mendes ◽

Michelle Livne ◽

...

Keyword(s):

Computed Tomography ◽

At Risk ◽

Deep Learning ◽

Clinical Practice ◽

Head And Neck ◽

Organs At Risk ◽

Data Set ◽

Computed Tomography Scans ◽

Neck Anatomy ◽

Organ At Risk

Background Over half a million individuals are diagnosed with head and neck cancer each year globally. Radiotherapy is an important curative treatment for this disease, but it requires manual time to delineate radiosensitive organs at risk. This planning process can delay treatment while also introducing interoperator variability, resulting in downstream radiation dose differences. Although auto-segmentation algorithms offer a potentially time-saving solution, the challenges in defining, quantifying, and achieving expert performance remain. Objective Adopting a deep learning approach, we aim to demonstrate a 3D U-Net architecture that achieves expert-level performance in delineating 21 distinct head and neck organs at risk commonly segmented in clinical practice. Methods The model was trained on a data set of 663 deidentified computed tomography scans acquired in routine clinical practice and with both segmentations taken from clinical practice and segmentations created by experienced radiographers as part of this research, all in accordance with consensus organ at risk definitions. Results We demonstrated the model’s clinical applicability by assessing its performance on a test set of 21 computed tomography scans from clinical practice, each with 21 organs at risk segmented by 2 independent experts. We also introduced surface Dice similarity coefficient, a new metric for the comparison of organ delineation, to quantify the deviation between organ at risk surface contours rather than volumes, better reflecting the clinical task of correcting errors in automated organ segmentations. The model’s generalizability was then demonstrated on 2 distinct open-source data sets, reflecting different centers and countries to model training. Conclusions Deep learning is an effective and clinically applicable technique for the segmentation of the head and neck anatomy for radiotherapy. With appropriate validation studies and regulatory approvals, this system could improve the efficiency, consistency, and safety of radiotherapy pathways.

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A proof-of-concept study on the use of prostate artery embolization prior to definitive radiotherapy in prostate cancer

10.21203/rs.3.rs-36761/v1 ◽

2020 ◽

Author(s):

Jeffrey Peacock ◽

Dhiraj Sikaria ◽

Laura Maun-Garcia ◽

Khosrow Javedan ◽

Kosj Yamoah ◽

...

Keyword(s):

Prostate Cancer ◽

Radiation Treatment ◽

Organs At Risk ◽

Statistical Significance ◽

Volume Reduction ◽

Proof Of Concept ◽

Artery Embolization ◽

Definitive Radiotherapy ◽

Prostate Artery Embolization

Abstract Backgrounds: Prostatic artery embolization (PAE) has been well studied as a clinically effective therapy for alleviating lower urinary tract symptoms (LUTS) in patients with benign prostatic hyperplasia (BPH). We demonstrate a proof of concept for PAE prior to definitive radiotherapy in patients with prostate cancer.Methods: From 12/2017 to 07/2019, 57 patients underwent PAE for LUTS and BPH. Nine of these patients had PAE for LUTS in the setting of localized prostate cancer prior to receiving radiation. Five of the nine patients received their entire radiotherapy course at our institution and had clinical follow up were included in the analysis. Median follow up was 18 months from the time of PAE. LUTS improvement quantified by IPSS was the primary endpoint and a two tail students T test was used to compare statistical significance. Side effects during radiation were quantified using the CTCAE scoring system. Pre- and post- PAE plans were compared in the five patients that by performing an isovolumetric expansion of the post PAE plan (treated plan) equivalent to the measured volume reduction after PAE. Patient 1 and 2 had prostate and seminal vesicle RT alone while patients 3-5 had prostate with elective nodal coverage. Mean doses to organs at risk were compared between the two plans.Results: The average IPSS score pre-PAE was 17.40 compared to post-PAE of 3.6 (p=0.02). The average IPSS score reduction after PAE was 13.8 (5-30). The average prostatic volume reduction after PAE was 23.14% (7.2% - 47.7%). There were no CTCAE grade 3 (severe) or higher during radiation treatment. Post-PAE plans in patient 1 and 2 had on average 16.7% and 39.8% decrease in mean dose across the bladder, rectum, and penile bulb compared to the pre-PAE plans. There were no appreciable differences in dosimetry in the patients 3-5 who had nodal coverage. There was no biochemical failure in any of the patients.Conclusion: We demonstrate a proof of concept that prostate artery embolization is useful as an adjunctive procedure to alleviate LUTS, achieve significant volume reduction prior to radiation therapy, and decrease radiation related toxicity in the treatment of prostate cancer.

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