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Rectum and Bladder Dose Variations During Prostate IGRT: An Evaluation of Bowel and Bladder Preparation Protocol
Poster Viewing Abstracts S395
Volume 84 Number 3S Supplement 2012 month CT may not account for volume changes from temporary prostatic edema during the majority of the dose deposition. Materials/Methods: Thirty-one patients were evaluated following Cs-131 prostate brachytherapy with QA-CT scans at days 0, 14, and 28 postimplant. From these QA-CT scans, we calculated prostatic volume and dosimetric parameters (D90, V100, V150, V200). We interpolated between these “snapshot” measurements for days between 0, 14, and 28 days to account for changing prostate volumes by fitting them to second order polynomial equations and then assumed unchanging volume after 28 days for the remaining isotope life. We correlated changing daily doses from Cs-131 to the measured or estimated changing prostate volumes to estimate the true dosimetric parameters over the life of the implant. Results: Pre-operative mean prostate volume was 39.8 cc. Mean prostate volumes post-operatively were highest at day0 (45.9cc), with subsequent decreases in volumes (day 14 Z 43.2cc, day 28 Z 37.7cc). The overall activity-time weighted summed D90 was 7.3% (+/-5.4%) higher than the day0 value, 2.1% (+/-3.2%) lower than the day14 value and 5.1% (+/-6.1%) lower than the day28 value. The effects of changing prostatic volume on estimates of V100, V150 and V200 appear similar. Conclusions: With any prostate implants, dosimetric parameter assessments may change significantly depending on when the post-operative QA-CT is done. This is especially true when using isotopes with short halflives. No single scan gives a completely accurate assessment, given the changing volume of the prostate over time due to edema. Hence, the true dosimetry over the life of the implant is in between the values that would obtained on a day 0 CT compared to a day 28 CT, and in fact the day 14 CT may be most accurate. This holds for longer half-life implants (I-125 and Pd-103), but because less radiation is delivered during the initial weeks of the implant, a single QI-CT at day 28 is more accurate than with Cs-131. The above calculations can help compare dosimetry across studies that report their dosimetry at different time points. Author Disclosure: R.P. Smith: None. J.C. Flickinger: None. T.S. Kehwar: None. R.M. Benoit: None. S. Beriwal: None.
2468 Rectum and Bladder Dose Variations During Prostate IGRT: An Evaluation of Bowel and Bladder Preparation Protocol A. Jotwani,1 J. Surendran,2 S. Chilukuri,3 R. Ramamohan,2 S. Ibrahim,2 and R. Shivakumar2; 1Surya Global Cancer Hospital, Kakinada, India, 2 Omega Hospital, Hyderabad, India, 3Yashoda Cancer Institute, Hyderabad, India Purpose: To quantify rectum and bladder doses during prostate radiation therapy using cone beam CT (CBCT) based image guidance with daily bowel and bladder preparation protocols in place. Material and Methods: An analysis of 304 CBCT images of 19 patients of localized prostatic adenocarcinoma treated by volumetric modulated arc therapy (VMAT) was carried out. CT simulation was performed with bladder and bowel preparation (empty bowel and bladder and drink 250mL water 1 hour before each treatment) and 2.5mm slice thickness. Total dose prescribed was 7800 cGy in 39 fractions (200 cGy/fraction). X-Ray volumetric Images were taken and registered online with the reference image in which simulation and planning is done and setup errors were corrected and documented before each treatment. CBCT image was then reconstructed with slice thickness 2.5 mm and fused with the planning CT scan using a mutual information algorithm with the threshold set to bony features (>150HU, bone-bone match). A total number of 16 CBCT image sets were analyzed for each patient (2 per week). Both rectum and bladder
Poster Viewing Abstract 2468; Table Volume fraction 50% 40% 25% 15%
Volume Volume Volume Volume
Mean planned rectum dose (cGy) 4932 5738 6829 7368
cGy cGy cGy cGy
(SD(SD(SD(SD-
92.91) 203.13) 258.34) 112.14)
were contoured on each CBCT image set by same radiation oncologist. Bladder- rectum volumes and respective doses were computed on simulation CT scan and all CBCT image sets according to the approved treatment plan. Result: Dose variations to different volume fractions of bladder and rectum are summarized in table below. Bladder and rectum dose variations were found to be more during second half of the treatment course as compared to first half. Notably, for rectum the average percent variation in mean dose was 5.34% during 1st week and 8.92% during last week of treatment. Similarly for urinary bladder the average percent variation in mean dose was 6.04% and 9.83% during 1st and last week respectively. Conclusions: With the current bowel- bladder preparation protocol there is a significant variation in actual measured doses to rectum and bladder as compared to the planned doses. In addition, there is a need for a more individualized and robust bowel-bladder preparation protocol especially during second half of treatment course to minimize this variation. Author Disclosure: A. Jotwani: None. J. Surendran: None. S. Chilukuri: None. R. Ramamohan: None. S. Ibrahim: None. R. Shivakumar: None.
2469 Identifying Prostate Cancer Subgroups With Decreased Survival Following Adjuvant Androgen Deprivation Therapy K.L. Maletz,1 R.D. Ennis,2,3 S. Kalnicki,4,3 G. Smith,2,5 and D. Goltz5,5; 1 University of Rochester, Rochester, NY, 2Continuum Cancer Centers of New York, New York, NY, 3Albert Einstein College of Medicine, Bronx, NY, 4 Montefiore Medical Center, Bronx, NY, 5St. Luke’s-Roosevelt Hospital Center, New York, NY Purpose/Objective(s): The use of adjuvant androgen deprivation therapy (AADT) may involve a tradeoff between improved prostate cancer control and increased cardiovascular (CV) mortality. While several studies have shown improved disease control with AADT, few have shown improved overall survival. Some have suggested that the CV harm of AADT is confined to those with pre-existing CV disease or the elderly. We examined the relationship between AADT and all-cause mortality in various subgroups, and the dependence of this relationship on existence or the development of CV risk factors. Materials/Methods: Patients with localized biopsy-proven prostate cancer between 2001 and 2011 were identified using a longitudinal electronic medical records database. Low, intermediate and high-risk prostate cancer was defined using the NCCN classification. AADT was given within one year of surgical or radiation therapy. Primary endpoint was all-cause mortality. CV risk factors were diabetes, hyperlipidemia (HLD), hypertension (HTN), congestive heart failure (CHF) and coronary artery disease (CAD). Correlation with chi-squared and Cox proportional hazard models was calculated. Results: Among 844 patients, 166 received AADT. Patients were 65.0 +/8.2 years old overall with AADT significantly older (69.8+/-7.9, p < 0.001). Higher risk prostate cancer groups were increasingly more likely to receive AADT (13% of low, 19% of intermediate and 36% of high-risk). Patients were followed for 4.9+/-2.5 years. Hazard ratio for all-cause mortality was increased with AADT after adjusting for age (HR 1.52, p Z 0.038), but not after accounting for age and prostate cancer risk group. For patients younger than or equal to 75 years, AADT increased risk of death (HR 2.3, p Z 0.001) even with adjustment for risk group. Diabetes incidence significantly increased (HR 2.0, p Z 0.001), but not for patients over 75 years of age (p Z 0.839). Incidence of HTN, HLD, CHF and CAD were
Actual measured rectum and bladder doses according to volume Mean measured rectum dose (cGy) 5264 6278 7274 7823
cGy cGy cGy cGy
(SD- 352.27) (SD- 260.01) (SD- 201.77) (SD 276.44)
Percentage variation in rectum dose (%)
Mean planned bladder dose (cGy)
Mean measured bladder dose (cGy)
Percentage variation in bladder dose (%)
6.73 9.42 6.52 6.18
5390 cGy (SD- 71.89) 6717 cGy (SD-100.62) 7299 cGy (SD- 288.12)
5784 cGy (SD- 187.15) 7182 cGy (SD-171.31) 7813 cGy (SD- 118.39)
7.4 6.92 7.04
Volume 84 Number 3S Supplement 2012 month CT may not account for volume changes from temporary prostatic edema during the majority of the dose deposition. Materials/Methods: Thirty-one patients were evaluated following Cs-131 prostate brachytherapy with QA-CT scans at days 0, 14, and 28 postimplant. From these QA-CT scans, we calculated prostatic volume and dosimetric parameters (D90, V100, V150, V200). We interpolated between these “snapshot” measurements for days between 0, 14, and 28 days to account for changing prostate volumes by fitting them to second order polynomial equations and then assumed unchanging volume after 28 days for the remaining isotope life. We correlated changing daily doses from Cs-131 to the measured or estimated changing prostate volumes to estimate the true dosimetric parameters over the life of the implant. Results: Pre-operative mean prostate volume was 39.8 cc. Mean prostate volumes post-operatively were highest at day0 (45.9cc), with subsequent decreases in volumes (day 14 Z 43.2cc, day 28 Z 37.7cc). The overall activity-time weighted summed D90 was 7.3% (+/-5.4%) higher than the day0 value, 2.1% (+/-3.2%) lower than the day14 value and 5.1% (+/-6.1%) lower than the day28 value. The effects of changing prostatic volume on estimates of V100, V150 and V200 appear similar. Conclusions: With any prostate implants, dosimetric parameter assessments may change significantly depending on when the post-operative QA-CT is done. This is especially true when using isotopes with short halflives. No single scan gives a completely accurate assessment, given the changing volume of the prostate over time due to edema. Hence, the true dosimetry over the life of the implant is in between the values that would obtained on a day 0 CT compared to a day 28 CT, and in fact the day 14 CT may be most accurate. This holds for longer half-life implants (I-125 and Pd-103), but because less radiation is delivered during the initial weeks of the implant, a single QI-CT at day 28 is more accurate than with Cs-131. The above calculations can help compare dosimetry across studies that report their dosimetry at different time points. Author Disclosure: R.P. Smith: None. J.C. Flickinger: None. T.S. Kehwar: None. R.M. Benoit: None. S. Beriwal: None.
2468 Rectum and Bladder Dose Variations During Prostate IGRT: An Evaluation of Bowel and Bladder Preparation Protocol A. Jotwani,1 J. Surendran,2 S. Chilukuri,3 R. Ramamohan,2 S. Ibrahim,2 and R. Shivakumar2; 1Surya Global Cancer Hospital, Kakinada, India, 2 Omega Hospital, Hyderabad, India, 3Yashoda Cancer Institute, Hyderabad, India Purpose: To quantify rectum and bladder doses during prostate radiation therapy using cone beam CT (CBCT) based image guidance with daily bowel and bladder preparation protocols in place. Material and Methods: An analysis of 304 CBCT images of 19 patients of localized prostatic adenocarcinoma treated by volumetric modulated arc therapy (VMAT) was carried out. CT simulation was performed with bladder and bowel preparation (empty bowel and bladder and drink 250mL water 1 hour before each treatment) and 2.5mm slice thickness. Total dose prescribed was 7800 cGy in 39 fractions (200 cGy/fraction). X-Ray volumetric Images were taken and registered online with the reference image in which simulation and planning is done and setup errors were corrected and documented before each treatment. CBCT image was then reconstructed with slice thickness 2.5 mm and fused with the planning CT scan using a mutual information algorithm with the threshold set to bony features (>150HU, bone-bone match). A total number of 16 CBCT image sets were analyzed for each patient (2 per week). Both rectum and bladder
Poster Viewing Abstract 2468; Table Volume fraction 50% 40% 25% 15%
Volume Volume Volume Volume
Mean planned rectum dose (cGy) 4932 5738 6829 7368
cGy cGy cGy cGy
(SD(SD(SD(SD-
92.91) 203.13) 258.34) 112.14)
were contoured on each CBCT image set by same radiation oncologist. Bladder- rectum volumes and respective doses were computed on simulation CT scan and all CBCT image sets according to the approved treatment plan. Result: Dose variations to different volume fractions of bladder and rectum are summarized in table below. Bladder and rectum dose variations were found to be more during second half of the treatment course as compared to first half. Notably, for rectum the average percent variation in mean dose was 5.34% during 1st week and 8.92% during last week of treatment. Similarly for urinary bladder the average percent variation in mean dose was 6.04% and 9.83% during 1st and last week respectively. Conclusions: With the current bowel- bladder preparation protocol there is a significant variation in actual measured doses to rectum and bladder as compared to the planned doses. In addition, there is a need for a more individualized and robust bowel-bladder preparation protocol especially during second half of treatment course to minimize this variation. Author Disclosure: A. Jotwani: None. J. Surendran: None. S. Chilukuri: None. R. Ramamohan: None. S. Ibrahim: None. R. Shivakumar: None.
2469 Identifying Prostate Cancer Subgroups With Decreased Survival Following Adjuvant Androgen Deprivation Therapy K.L. Maletz,1 R.D. Ennis,2,3 S. Kalnicki,4,3 G. Smith,2,5 and D. Goltz5,5; 1 University of Rochester, Rochester, NY, 2Continuum Cancer Centers of New York, New York, NY, 3Albert Einstein College of Medicine, Bronx, NY, 4 Montefiore Medical Center, Bronx, NY, 5St. Luke’s-Roosevelt Hospital Center, New York, NY Purpose/Objective(s): The use of adjuvant androgen deprivation therapy (AADT) may involve a tradeoff between improved prostate cancer control and increased cardiovascular (CV) mortality. While several studies have shown improved disease control with AADT, few have shown improved overall survival. Some have suggested that the CV harm of AADT is confined to those with pre-existing CV disease or the elderly. We examined the relationship between AADT and all-cause mortality in various subgroups, and the dependence of this relationship on existence or the development of CV risk factors. Materials/Methods: Patients with localized biopsy-proven prostate cancer between 2001 and 2011 were identified using a longitudinal electronic medical records database. Low, intermediate and high-risk prostate cancer was defined using the NCCN classification. AADT was given within one year of surgical or radiation therapy. Primary endpoint was all-cause mortality. CV risk factors were diabetes, hyperlipidemia (HLD), hypertension (HTN), congestive heart failure (CHF) and coronary artery disease (CAD). Correlation with chi-squared and Cox proportional hazard models was calculated. Results: Among 844 patients, 166 received AADT. Patients were 65.0 +/8.2 years old overall with AADT significantly older (69.8+/-7.9, p < 0.001). Higher risk prostate cancer groups were increasingly more likely to receive AADT (13% of low, 19% of intermediate and 36% of high-risk). Patients were followed for 4.9+/-2.5 years. Hazard ratio for all-cause mortality was increased with AADT after adjusting for age (HR 1.52, p Z 0.038), but not after accounting for age and prostate cancer risk group. For patients younger than or equal to 75 years, AADT increased risk of death (HR 2.3, p Z 0.001) even with adjustment for risk group. Diabetes incidence significantly increased (HR 2.0, p Z 0.001), but not for patients over 75 years of age (p Z 0.839). Incidence of HTN, HLD, CHF and CAD were
Actual measured rectum and bladder doses according to volume Mean measured rectum dose (cGy) 5264 6278 7274 7823
cGy cGy cGy cGy
(SD- 352.27) (SD- 260.01) (SD- 201.77) (SD 276.44)
Percentage variation in rectum dose (%)
Mean planned bladder dose (cGy)
Mean measured bladder dose (cGy)
Percentage variation in bladder dose (%)
6.73 9.42 6.52 6.18
5390 cGy (SD- 71.89) 6717 cGy (SD-100.62) 7299 cGy (SD- 288.12)
5784 cGy (SD- 187.15) 7182 cGy (SD-171.31) 7813 cGy (SD- 118.39)
7.4 6.92 7.04