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Title: Evaluation of volume change in rectum and bladder during application of image-guided radiotherapy for prostate carcinoma

Abstract

All prostate cancer patients from Centro Médico Radioterapia Siglo XXI receive Volumetric Modulated Arc Therapy (VMAT). This therapy uses image-guided radiotherapy (IGRT) with the Cone Beam Computed Tomography (CBCT). This study compares the planned dose in the reference CT image against the delivered dose recalculate in the CBCT image. The purpose of this study is to evaluate the anatomic changes and related dosimetric effect based on weekly CBCT directly for patients with prostate cancer undergoing volumetric modulated arc therapy (VMAT) treatment. The collected data were analyzed using one-way ANOVA.

Authors:
 [1];  [2];  [3]
  1. Departamento de Física, Universidad Nacional de Costa Rica, Heredia (Costa Rica)
  2. Centro Médico Radioterapia Siglo XX1, La Uruca (Costa Rica)
  3. (Costa Rica)
Publication Date:
OSTI Identifier:
22608538
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1753; Journal Issue: 1; Conference: Latin American symposium on nuclear physics and applications, Medellin (Colombia), 30 Nov - 4 Dec 2015; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; BEAMS; BLADDER; CARCINOMAS; CAT SCANNING; COMPARATIVE EVALUATIONS; COMPUTERIZED TOMOGRAPHY; IMAGES; PATIENTS; PROSTATE; RADIATION DOSES; RADIOTHERAPY; RECTUM

Citation Formats

Luna, J. A., E-mail: yosimoon13@hotmail.com, Rojas, J. I., E-mail: isaac.rojas@siglo21.cr, and PROXTRONICS CR, Ltda, Heredia. Evaluation of volume change in rectum and bladder during application of image-guided radiotherapy for prostate carcinoma. United States: N. p., 2016. Web. doi:10.1063/1.4955392.
Luna, J. A., E-mail: yosimoon13@hotmail.com, Rojas, J. I., E-mail: isaac.rojas@siglo21.cr, & PROXTRONICS CR, Ltda, Heredia. Evaluation of volume change in rectum and bladder during application of image-guided radiotherapy for prostate carcinoma. United States. doi:10.1063/1.4955392.
Luna, J. A., E-mail: yosimoon13@hotmail.com, Rojas, J. I., E-mail: isaac.rojas@siglo21.cr, and PROXTRONICS CR, Ltda, Heredia. 2016. "Evaluation of volume change in rectum and bladder during application of image-guided radiotherapy for prostate carcinoma". United States. doi:10.1063/1.4955392.
@article{osti_22608538,
title = {Evaluation of volume change in rectum and bladder during application of image-guided radiotherapy for prostate carcinoma},
author = {Luna, J. A., E-mail: yosimoon13@hotmail.com and Rojas, J. I., E-mail: isaac.rojas@siglo21.cr and PROXTRONICS CR, Ltda, Heredia},
abstractNote = {All prostate cancer patients from Centro Médico Radioterapia Siglo XXI receive Volumetric Modulated Arc Therapy (VMAT). This therapy uses image-guided radiotherapy (IGRT) with the Cone Beam Computed Tomography (CBCT). This study compares the planned dose in the reference CT image against the delivered dose recalculate in the CBCT image. The purpose of this study is to evaluate the anatomic changes and related dosimetric effect based on weekly CBCT directly for patients with prostate cancer undergoing volumetric modulated arc therapy (VMAT) treatment. The collected data were analyzed using one-way ANOVA.},
doi = {10.1063/1.4955392},
journal = {AIP Conference Proceedings},
number = 1,
volume = 1753,
place = {United States},
year = 2016,
month = 7
}
  • Purpose: The purpose of this study was to analyze the relationship between prostate, bladder, and rectum volumes on treatment planning CT day and prostate shifts in the XYZ directions on treatment days. Methods: Prostate, seminal vesicles, bladder, and rectum were contoured on CT images obtained in supine position. Intensity modulated radiation therapy plans was prepared. Contours were exported to BAT-ultrasound imaging system. Patients were positioned on the couch using skin marks. An ultrasound probe was used to obtain ultrasound images of prostate, bladder, and rectum, which were aligned with CT images. Couch shifts in the XYZ directions as recommended bymore » BAT system were made and recorded. 4698 couch shifts for 42 patients were analyzed to study the correlations between interfraction prostate shifts vs bladder, rectum, and prostate volumes on planning CT. Results: Mean and range of volumes (cc): Bladder: 179 (42-582), rectum: 108 (28-223), and prostate: 55 (21-154). Mean systematic prostate shifts were (cm, {+-}SD) right and left lateral: -0.047{+-}0.16 (-0.361-0.251), anterior and posterior: 0.14{+-}0.3 (-0.466-0.669), and superior and inferior: 0.19{+-}0.26 (-0.342-0.633). Bladder volume was not correlated with lateral, anterior/posterior, and superior/inferior prostate shifts (P>0.2). Rectal volume was correlated with anterior/posterior (P<0.001) but not with lateral and superior/inferior prostate shifts (P>0.2). The smaller the rectal volume or cross sectional area, the larger was the prostate shift anteriorly and vice versa (P<0.001). Prostate volume was correlated with superior/inferior (P<0.05) but not with lateral and anterior/posterior prostate shifts (P>0.2). The smaller the prostate volume, the larger was prostate shift superiorly and vice versa (P<0.05). Conclusions: Prostate and rectal volumes, but not bladder volumes, on treatment planning CT influenced prostate position on treatment fractions. Daily image-guided adoptive radiotherapy would be required for patients with distended or empty rectum on planning CT to reduce rectal toxicity in the case of empty rectum and to minimize geometric miss of prostate.« less
  • Purpose: To identify dosimetric variables predictive of acute gastrointestinal (GI) and genitourinary (GU) toxicity and to determine whether hormonal therapy (HT) is independently associated with acute GI and GU toxicity in prostate cancer patients treated with conformal radiotherapy (RT). Methods and Materials: This analysis was performed on 336 patients participating in a multicenter (four hospitals) randomized trial comparing 68 Gy and 78 Gy. The clinical target volume consisted of the prostate with or without the seminal vesicles, depending on the risk of seminal vesicle involvement. The margin from the clinical target volume to the planning target volume was 1 cm.more » For these patients, the treatment plan for a total dose of 68 Gy was used, because nearly all toxicity appeared before the onset of the 10-Gy boost. Acute toxicity (<120 days) was scored according to the Radiation Therapy Oncology Group criteria. The dosimetric parameters were obtained from the relative and absolute dose-volume/surface histograms derived from the rectal wall (rectal wall volume receiving {>=}5-65 Gy) and the bladder surface (bladder surface receiving {>=}5-65 Gy). Additionally, relative and absolute dose-length histograms of the rectum were created, and the lengths of rectum receiving more than a certain dose over the whole circumference (rectal length receiving {>=}5-65 Gy) were computed. The clinical variables taken into account for GI toxicity were neoadjuvant HT, hospital, and dose-volume group; for GU toxicity, the variables pretreatment GU symptoms, neoadjuvant HT, and transurethral resection of the prostate were analyzed. The variable neoadjuvant HT was divided into three categories: no HT, short-term neoadjuvant HT (started {<=}3 months before RT), and long-term neoadjuvant HT (started >3 months before RT). Results: Acute GI toxicity Grade 2 or worse was seen in 46% of the patients. Patients with long-term neoadjuvant HT experienced less Grade 2 or worse toxicity (27%) compared with those receiving short-term neoadjuvant HT (50%) and no HT (50%). The volumes of the prostate and seminal vesicles were significantly smaller in both groups receiving neoadjuvant HT compared with those receiving no HT. In multivariate logistic regression analysis, including the two statistically significant clinical variables neoadjuvant HT and hospital, a volume effect was found for the relative, as well as absolute, rectal wall volumes exposed to intermediate and high doses. Of all the length parameters, the relative rectal length irradiated to doses of {>=}5 Gy and {>=}30 Gy and absolute lengths receiving {>=}5-15 and 30 Gy were significant. Acute GU toxicity Grade 2 or worse was reported in 56% of cases. For patients with pretreatment GU symptoms, the rate was 93%. The use of short-term and long-term neoadjuvant HT resulted in more GU toxicity (73% and 71%) compared with no HT (50%). In multivariate analysis, containing the variables pretreatment symptoms and neoadjuvant HT, only the absolute dose-surface histogram parameters (absolute surface irradiated to {>=}40, 45, and 65 Gy) were significantly associated with acute GU toxicity. Conclusion: A volume effect was found for acute GI toxicity for relative, as well as absolute, volumes. With regard to acute GU toxicity, an area effect was found, but only for absolute dose-surface histogram parameters. Neoadjuvant HT appeared to be an independent prognostic factor for acute toxicity, resulting in less acute GI toxicity, but more acute GU toxicity. The presence of pretreatment GU symptoms was the most important prognostic factor for GU symptoms during RT.« less
  • Purpose: To quantify and evaluate the accumulated prostate, rectum, and bladder dose for several strategies including rotational organ motion correction for intensity-modulated radiotherapy (IMRT) of prostate cancer using realistic organ motion data. Methods and Materials: Repeat computed tomography (CT) scans of 19 prostate patients were used. Per patient, two IMRT plans with different uniform margins were created. To quantify prostate and seminal vesicle motion, repeat CT clinical target volumes (CTVs) were matched onto the planning CTV using deformable registration. Four different strategies, from online setup to full motion correction, were simulated. Rotations were corrected for using gantry and collimator anglemore » adjustments. Prostate, rectum, and bladder doses were accumulated for each patient, plan, and strategy. Minimum CTV dose (D{sub min}), rectum equivalent uniform dose (EUD, n = 0.13), and bladder surface receiving >=78 Gy (S78), were calculated. Results: With online CTV translation correction, a 7-mm margin was sufficient (i.e., D{sub min} >= 95% of the prescribed dose for all patients). A 4-mm margin required additional rotational correction. Margin reduction lowered the rectum EUD(n = 0.13) by approx2.6 Gy, and the bladder S78 by approx1.9%. Conclusions: With online correction of both translations and rotations, a 4-mm margin was sufficient for 15 of 19 patients, whereas the remaining four patients had an underdosed CTV volume <1%. Margin reduction combined with online corrections resulted in a similar or lower dose to the rectum and bladder. The more advanced the correction strategy, the better the planned and accumulated dose agreed.« less
  • Purpose: To review 1870 CT scans of interfractional prostate shift obtained during image-guided radiotherapy. Methods and Materials: A total of 1870 pretreatment CT scans were acquired with CT-on-rails, and the corresponding shift data for 329 patients with prostate cancer were analyzed. Results: Of the 1870 scans reviewed, 44% required no setup adjustments in the anterior-posterior (AP) direction, 14% had shifts of 3-5 mm, 29% had shifts of 6-10 mm, and 13% had shifts of >10 mm. In the superior-inferior direction, 81% had no adjustments, 2% had shifts of 3-5 mm, 15% had shifts of 6-10 mm, and 2% had shiftsmore » of >10 mm. In the left-right direction, 65% had no adjustment, 13% had shifts of 3-5 mm, 17% had shifts of 6-10 mm, and 5% had shifts of >10 mm. Further analysis of the first 66 consecutive patients divided into three groups according to body mass index indicates that the shift in the AP direction for the overweight subgroup was statistically larger than those for the control and obese subgroups (p < 0.05). The interfractional shift in the lateral direction for the obese group (1 SD, 5.5 mm) was significantly larger than those for the overweight and control groups (4.1 and 2.9 mm, respectively) (p < 0.001). Conclusions: These data demonstrate that there is a significantly greater shift in the AP direction than in the lateral and superior-inferior directions for the entire patient group. Overweight and obese patient groups show a significant difference from the control group in terms of prostate shift.« less
  • Purpose: Setup errors and prostate intrafraction motion are main sources of localization uncertainty in prostate cancer radiation therapy. This study evaluates four different imaging modalities 3D ultrasound (US), kV planar images, cone-beam computed tomography (CBCT), and implanted electromagnetic transponders (Calypso/Varian) to assess inter- and intrafraction localization errors during intensity-modulated radiation therapy based treatment of prostate cancer. Methods: Twenty-seven prostate cancer patients were enrolled in a prospective IRB-approved study and treated to a total dose of 75.6 Gy (1.8 Gy/fraction). Overall, 1100 fractions were evaluated. For each fraction, treatment targets were localized using US, kV planar images, and CBCT in amore » sequence defined to determine setup offsets relative to the patient skin tattoos, intermodality differences, and residual errors for each patient and patient cohort. Planning margins, following van Herk's formalism, were estimated based on error distributions. Calypso-based localization was not available for the first eight patients, therefore centroid positions of implanted gold-seed markers imaged prior to and immediately following treatment were used as a motion surrogate during treatment. For the remaining 19 patients, Calypso transponders were used to assess prostate intrafraction motion. Results: The means ({mu}), and standard deviations (SD) of the systematic ({Sigma}) and random errors ({sigma}) of interfraction prostate shifts (relative to initial skin tattoo positioning), as evaluated using CBCT, kV, and US, averaged over all patients and fractions, were: [{mu}{sub CBCT}= (-1.2, 0.2, 1.1) mm, {Sigma}{sub CBCT}= (3.0, 1.4, 2.4) mm, {sigma}{sub CBCT}= (3.2, 2.2, 2.5) mm], [{mu}{sub kV}= (-2.9, -0.4, 0.5) mm, {Sigma}{sub kV}= (3.4, 3.1, 2.6) mm, {sigma}{sub kV}= (2.9, 2.0, 2.4) mm], and [{mu}{sub US}= (-3.6, -1.4, 0.0) mm, {Sigma}{sub US}= (3.3, 3.5, 2.8) mm, {sigma}{sub US}= (4.1, 3.8, 3.6) mm], in the anterior-posterior (A/P), superior-inferior (S/I), and the left-right (L/R) directions, respectively. In the treatment protocol, adjustment of couch was guided by US images. Residual setup errors as assessed by kV images were found to be: {mu}{sub residual}= (-0.4, 0.2, 0.2) mm, {Sigma}{sub residual}= (1.0, 1.0,0.7) mm, and {sigma}{sub residual}= (2.5, 2.3, 1.8) mm. Intrafraction prostate motion, evaluated using electromagnetic transponders, was: {mu}{sub intrafxn}= (0.0, 0.0, 0.0) mm, {Sigma}{sub intrafxn}= (1.3, 1.5, 0.6) mm, and {sigma}{sub intrafxn}= (2.6, 2.4, 1.4) mm. Shifts between pre- and post-treatment kV images were: {mu}{sub kV(post-pre)}= (-0.3, 0.8, -0.2), {Sigma}{sub kV(post-pre)}= (2.4, 2.7, 2.1) mm, and {sigma}{sub kV(post-pre)}= (2.7, 3.2, 3.1) mm. Relative to skin tattoos, planning margins for setup error were within 10-11 mm for all image-based modalities. The use of image guidance was shown to reduce these margins to less than 5 mm. Margins to compensate for both residual setup (interfraction) errors as well as intrafraction motion were 6.6, 6.8, and 3.9 mm in the A/P, S/I, and L/R directions, respectively. Conclusions: Analysis of interfraction setup errors, performed with US, CBCT, planar kV images, and electromagnetic transponders, from a large dataset revealed intermodality shifts were comparable (within 3-4 mm). Interfraction planning margins, relative to setup based on skin marks, were generally within the 10 mm prostate-to-planning target volume margin used in our clinic. With image guidance, interfraction residual planning margins were reduced to approximately less than 4 mm. These findings are potentially important for dose escalation studies using smaller margins to better protect normal tissues.« less