- Email: [email protected]
gas Volume Changes For Patients Undergoing Radiotherapy With Daily Endorectal Balloon?
I. J. Radiation Oncology d Biology d Physics
S444
Volume 81, Number 2, Supplement, 2011
Conclusions: High dose IMRT following cryotherapy failure is well tolerated without severe acute or late morbidity. This study supports the use of salvage radiation for cryotherapy failure for prostate adenocarcinoma. Pelvic lymph node irradiation was well tolerated and may improve salvage. Author Disclosure: M. Choi: None. C.R. Kim: None. A.Y. Hung: None.
2486
The Importance of an Exponential PSA Decline After External Beam Radiotherapy For Intermediate Risk Prostate Cancer
G. Delouya1, G. Kaufman2, M. Sylvestre3, T. Nguyen1, J. Bahary1, D. Taussky1, P. Despres1 1 Centre Hospitalier de l’Universite de Montreal (CHUM), Montreal, QC, Canada, 2Centre de Recherche, CHU Sainte-Justine, Montreal, QC, Canada, 3Service de Consultation en Biostatistique du Centre de Recherche du Centre Hospitalier de l’Universite de Montreal (CRCHUM), Montreal, QC, Canada
Purpose/Objective(s): To study the influence of an exponential Prostate-Specific Antigen (PSA) decline on biochemical failure after external-beam radiotherapy (EBRT) in a randomized prospective study for intermediate-risk prostate cancer. Materials/Methods: We analyzed 114 patients with intermediate risk prostate cancer (Gleason # 6 and PSA 10-20 or Gleason 7 and PSA \10). Patients were randomized between EBRT doses of either 70.2 Gy or 79.2 Gy (1.8 Gy per day). All patients had a follow up of at least six PSA measurements post-EBRT. Seventeen patients experienced biochemical failure (Phoenix definition). Whether a decline was exponential or not was calculated over 6 PSA measurements. Exponential decline and PSA half life were included in a Cox regression analysis for factors associated with biochemical failure. A multivariate logistic model was used to define predictors of an exponential decline. Results: A total of 80 /114 (70.2%) patterns were classified as having an exponential PSA decline. Both exponential decline (HR 0.115, 95%CI 0.03-0.44, p = 0.0016) and PSA half life ratio (PSA half life / number of days from end of treatment to the sixth post- EBRT visit) were statistically significant predictors (HR 1.03 (95% CI 1.01 - 1.06) of biochemical failure. In the multivariate linear model predicting for factors having an influence on PSA half life ratio, body mass index (BMI) (p = 0.056) and percentage of positive biopsies (p = 0.047) were borderline statistically significant. In the model predicting for exponential decline, none of the factors were significant, not even BMI (p = 0.11), or percentage of positive biopsies (p = 0.20). Radiation dose had no influence on either biochemical failure or PSA half life ratio. Conclusions: Patients with an exponential PSA decline show a better biochemical outcome in the long term. Exponential PSA decline and PSA half life are both independent of radiation dose. Author Disclosure: G. Delouya: None. G. Kaufman: None. M. Sylvestre: None. T. Nguyen: None. J. Bahary: None. D. Taussky: None. P. Despres: None.
2487
Is Prostate Inter- And Intrafraction Motion Dependent On Stool/gas Volume Changes For Patients Undergoing Radiotherapy With Daily Endorectal Balloon?
K. Wang1, N. Vapiwala1, C. Deville1, J. P. Plastaras1, V. Bui1, V. Bar Ad2, Z. Tochner1, S. Both1 1
University of Pennsylvania, Philadelphia, PA, 2Jefferson University, Philadelphia, PA
Purpose/Objective(s): Highly conformal prostate radiotherapy (RT) techniques mandate accurate and reproducible target localization. Daily variations in rectal filling with gas and/or stool may contribute to inter- and intrafraction prostate motion during RT. We investigate the impact of these variations on prostate motion during RT with daily endorectal balloon (ERB). Materials/Methods: Thirty patients undergoing prostate RT with daily ERB, radiofrequency-guided RT, and weekly CBCT were prospectively enrolled on this IRB-approved study at the Hospital of the University of Pennsylvania. The ERB with indexed lumen was inserted into rectum and filled with 100mL of water. A total of 197 treatment sessions were used to analyze the impact of stool/gas volume variability on prostate displacement over the RT course. The corresponding tracking data was evaluated for initial prostate localization and intrafraction motion during each treatment session, based on 3D, lateral (L), cranial-caudal (CC), and anterior-posterior (AP) displacements. For intrafraction motion, the average prostate motion within 1 minute intervals for up to 6 minutes of treatment time was calculated. For the correlation analysis of stool/gas volume with motion, patients were classified into two groups: small (\15 cc) vs. large volume ($ 15 cc). Results: The magnitude of prostate intrafraction in 3D, L, CC, and AP directions increased with elapsed treatment time (p\0.05). However, for both the small and large stool/gas volume groups, no consistent pattern of intrafraction motion correlated to the volume in any of the directions during the analyzed treatment time (p.0.05). In terms of interfraction motion, no significant correlation between the initial localization uncertainty and stool/gas volume were demonstrated in this study (p.0.05). Conclusions: Our preliminary analysis suggests that stool/gas volume variability during prostate RT may not impact inter- or intrafraction prostate motion when a daily ERB is employed. This study renders that with ERB, stool/gas variations may be inconsequential to the treatment outcome. Author Disclosure: K. Wang: None. N. Vapiwala: None. C. Deville: None. J.P. Plastaras: None. V. Bui: None. V. Bar Ad: None. Z. Tochner: None. S. Both: None.
2488
A Dosimetric Comparison of IMPT, DSPT, and IMRT for Low Risk Prostate Cancer
M. N. Corradetti, N. Vapiwala, H. Zhai, H. Lin, V. Bui, C. Deville, J. Bekelman, J. Christodouleas, Z. Tochner, S. Both University of Pennsylvania, Philadelphia, PA Purpose/Objective(s): Intensity modulated radiotherapy (IMRT) is a mainstay of treatment for prostate adenocarcinoma, along with brachytherapy, prostatectomy, and active surveillance. The aim of this study is to compare the dose
S444
Volume 81, Number 2, Supplement, 2011
Conclusions: High dose IMRT following cryotherapy failure is well tolerated without severe acute or late morbidity. This study supports the use of salvage radiation for cryotherapy failure for prostate adenocarcinoma. Pelvic lymph node irradiation was well tolerated and may improve salvage. Author Disclosure: M. Choi: None. C.R. Kim: None. A.Y. Hung: None.
2486
The Importance of an Exponential PSA Decline After External Beam Radiotherapy For Intermediate Risk Prostate Cancer
G. Delouya1, G. Kaufman2, M. Sylvestre3, T. Nguyen1, J. Bahary1, D. Taussky1, P. Despres1 1 Centre Hospitalier de l’Universite de Montreal (CHUM), Montreal, QC, Canada, 2Centre de Recherche, CHU Sainte-Justine, Montreal, QC, Canada, 3Service de Consultation en Biostatistique du Centre de Recherche du Centre Hospitalier de l’Universite de Montreal (CRCHUM), Montreal, QC, Canada
Purpose/Objective(s): To study the influence of an exponential Prostate-Specific Antigen (PSA) decline on biochemical failure after external-beam radiotherapy (EBRT) in a randomized prospective study for intermediate-risk prostate cancer. Materials/Methods: We analyzed 114 patients with intermediate risk prostate cancer (Gleason # 6 and PSA 10-20 or Gleason 7 and PSA \10). Patients were randomized between EBRT doses of either 70.2 Gy or 79.2 Gy (1.8 Gy per day). All patients had a follow up of at least six PSA measurements post-EBRT. Seventeen patients experienced biochemical failure (Phoenix definition). Whether a decline was exponential or not was calculated over 6 PSA measurements. Exponential decline and PSA half life were included in a Cox regression analysis for factors associated with biochemical failure. A multivariate logistic model was used to define predictors of an exponential decline. Results: A total of 80 /114 (70.2%) patterns were classified as having an exponential PSA decline. Both exponential decline (HR 0.115, 95%CI 0.03-0.44, p = 0.0016) and PSA half life ratio (PSA half life / number of days from end of treatment to the sixth post- EBRT visit) were statistically significant predictors (HR 1.03 (95% CI 1.01 - 1.06) of biochemical failure. In the multivariate linear model predicting for factors having an influence on PSA half life ratio, body mass index (BMI) (p = 0.056) and percentage of positive biopsies (p = 0.047) were borderline statistically significant. In the model predicting for exponential decline, none of the factors were significant, not even BMI (p = 0.11), or percentage of positive biopsies (p = 0.20). Radiation dose had no influence on either biochemical failure or PSA half life ratio. Conclusions: Patients with an exponential PSA decline show a better biochemical outcome in the long term. Exponential PSA decline and PSA half life are both independent of radiation dose. Author Disclosure: G. Delouya: None. G. Kaufman: None. M. Sylvestre: None. T. Nguyen: None. J. Bahary: None. D. Taussky: None. P. Despres: None.
2487
Is Prostate Inter- And Intrafraction Motion Dependent On Stool/gas Volume Changes For Patients Undergoing Radiotherapy With Daily Endorectal Balloon?
K. Wang1, N. Vapiwala1, C. Deville1, J. P. Plastaras1, V. Bui1, V. Bar Ad2, Z. Tochner1, S. Both1 1
University of Pennsylvania, Philadelphia, PA, 2Jefferson University, Philadelphia, PA
Purpose/Objective(s): Highly conformal prostate radiotherapy (RT) techniques mandate accurate and reproducible target localization. Daily variations in rectal filling with gas and/or stool may contribute to inter- and intrafraction prostate motion during RT. We investigate the impact of these variations on prostate motion during RT with daily endorectal balloon (ERB). Materials/Methods: Thirty patients undergoing prostate RT with daily ERB, radiofrequency-guided RT, and weekly CBCT were prospectively enrolled on this IRB-approved study at the Hospital of the University of Pennsylvania. The ERB with indexed lumen was inserted into rectum and filled with 100mL of water. A total of 197 treatment sessions were used to analyze the impact of stool/gas volume variability on prostate displacement over the RT course. The corresponding tracking data was evaluated for initial prostate localization and intrafraction motion during each treatment session, based on 3D, lateral (L), cranial-caudal (CC), and anterior-posterior (AP) displacements. For intrafraction motion, the average prostate motion within 1 minute intervals for up to 6 minutes of treatment time was calculated. For the correlation analysis of stool/gas volume with motion, patients were classified into two groups: small (\15 cc) vs. large volume ($ 15 cc). Results: The magnitude of prostate intrafraction in 3D, L, CC, and AP directions increased with elapsed treatment time (p\0.05). However, for both the small and large stool/gas volume groups, no consistent pattern of intrafraction motion correlated to the volume in any of the directions during the analyzed treatment time (p.0.05). In terms of interfraction motion, no significant correlation between the initial localization uncertainty and stool/gas volume were demonstrated in this study (p.0.05). Conclusions: Our preliminary analysis suggests that stool/gas volume variability during prostate RT may not impact inter- or intrafraction prostate motion when a daily ERB is employed. This study renders that with ERB, stool/gas variations may be inconsequential to the treatment outcome. Author Disclosure: K. Wang: None. N. Vapiwala: None. C. Deville: None. J.P. Plastaras: None. V. Bui: None. V. Bar Ad: None. Z. Tochner: None. S. Both: None.
2488
A Dosimetric Comparison of IMPT, DSPT, and IMRT for Low Risk Prostate Cancer
M. N. Corradetti, N. Vapiwala, H. Zhai, H. Lin, V. Bui, C. Deville, J. Bekelman, J. Christodouleas, Z. Tochner, S. Both University of Pennsylvania, Philadelphia, PA Purpose/Objective(s): Intensity modulated radiotherapy (IMRT) is a mainstay of treatment for prostate adenocarcinoma, along with brachytherapy, prostatectomy, and active surveillance. The aim of this study is to compare the dose