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One Size Doesn't Fit All: The Value of Adaptive Radiotherapy (ART) Planning Methods using Daily Image Guidance in Bladder Radiotherapy (RT)
Proceedings of the 50th Annual ASTRO Meeting Results: A total of 3,924 fiducials were inserted in 1,021 patients for fiducial-based kV prostate IGRT. Of those, only 1 patient developed urosepsis attributable to the placement of fiducial markers yielding a urosepsis rate of 0.098% per patient or 0.025% per marker placed. This patient had three prior needle biopsies of the prostate, the second of which resulted in urosepsis under levofloxacin prophylaxis. Urosepsis occurred again 8 months later after fiducial marker placement despite broader antibiotic coverage with levofloxacin and nitrofurantoin. i.v. antibiotics successfully treated both septic events without any long-term consequences. Other patients known to have developed sepsis following prostate biopsy did not develop sepsis following fiducial marker placement when given broader antibiotic coverage. Conclusions: Based on one of the largest cohorts of patients undergoing fiducial-based kV IGRT for prostate cancer, the risk of urosepsis due to implantation of soft-tissue fiducial markers for IGRT is rare. The development of urosepsis after prostate biopsy may be a risk factor for the subsequent development of urosepsis after fiducial marker placement and broader antibiotic coverage may eliminate this risk. The use of transrectal ultrasound placement of intraprostatic fiducial soft-tissue markers for IGRT is safe and with typical pre-procedural preparation carries close to no risk of urosepsis. Author Disclosure: E. Obedian, None; D.A. Kapoor, None; C.A. Olsson, None; S.H. Zimberg, None.
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One Size Doesn’t Fit All: The Value of Adaptive Radiotherapy (ART) Planning Methods using Daily Image Guidance in Bladder Radiotherapy (RT)
S. Lalondrelle1, V. N. Hansen1, H. McNair1, R. Huddart2, A. Horwich2, D. Dearnaley2, V. Khoo3 1 3
Royal Marsden NHS Foundation Trust, Sutton, United Kingdom, 2Institute of Cancer Research, Sutton, United Kingdom, Royal Marsden NHS Foundation Trust, London, United Kingdom
Purpose/Objective(s): To determine whether adapting treatment plans using a plan selection method based on individual bladder filling patterns (A-POLO, adaptive-predictive organ localization) or using a composite volume (CV) technique provides greater improvement in accuracy during a radical course of bladder RT. Materials/Methods: A post void CT was used to define the clinical target volume, CTV1, for the whole bladder with 1.5 cm isotropic margins to generate the planning target volume, PTV1. During 32 fractions, a daily preRT cone beam CT (CBCT) was taken and retrospectively assessed. A need for ART was defined as displacement of the CBCT bladder contour (CTVcb) to within 5 mm of PTV1 in any direction on any occasion. A-POLO methodology: Additional CT planning scans were performed at 15 and 30 minutes (CT2, 3) post void to document individual patterns of bladder filling and organ motion and used to generate a library of patient-specific volumes (PTV2, 3) by adding 1.5 cm margins to CTV2, 3. From the start of RT, for each fraction needing ART the most appropriate PTV for each day was chosen from the patient’s library (i.e., PTV1, 2 or 3). CV methodology: A further CTV (CTV4) was created using CTV1 and CTVcb from Days 1-4 of treatment to define the maximum excursions of the bladder with isotropic margins of 5mm to form PTV4. This method was assessed from Day 5 onwards. The methods were compared for correction of geographic miss overall and individually. Results: The 108 RT fractions in 5 patients were assessed. Mean (range) PTV1, 2, 3 and 4 was 411.57 cc (334-511), 462 cc (360564), 482 cc (393-570) and 323 cc (285-394). During RT the mean PTVcb was 234cc (135-558) with mean interfraction (IF) translations of 0.4 cm (-1.6 to 3.7) cranially and 0.3 cm (-0.85 to 3.25) anteriorly. Overall 57% (range, 4-96%) of fractions needed ART in 100% of patients with up to 35% of PTVcb excluded. Using the A-POLO method 79% were corrected, 53% using the CV method. For adapted fractions where the PTVcb was not entirely covered by either model A-POLO left a smaller mean residual volume untreated, 4% vs. 9.1%. The mean CTVcb-selected PTV margin was .1cm (range, 1-1.5) in all dimensions with APOLO and \0.95 cm (range, 0.6-0.95) aside for cranially (1.4cm) using CV. Individually, 3 patients benefited most from an A-POLO method, 1 patient from a CV method, 1 benefited equally with either method. Conclusions: If variation in bladder size and shape is unpredictable, all patients could benefit from frequent image guidance and ART. Using a plan selection method may provide greater accuracy but requires daily imaging and intervention. The CV method results in smaller treatment volumes but does not model for large variations. A-POLO could be optimized by using anisotropic margins. On-going work will define these benefits. Author Disclosure: S. Lalondrelle, None; V.N. Hansen, None; H. McNair, None; R. Huddart, None; A. Horwich, None; D. Dearnaley, None; V. Khoo, None.
2349
Analysis of Biochemical Control, Prognostic Factors and Toxicities in Patients Treated with Intensity Modulated Radiotherapy for Localized Prostate Cancer with Longer Follow-up
S. A. Vora, W. W. Wong, S. E. Schild, G. A. Ezzell Mayo Clinic Arizona, Scottsdale, AZ Purpose/Objective(s): To review biochemical control rates, prognostic factors and toxicities (acute and chronic) for patients treated with intensity-modulated radiation therapy (IMRT). Materials/Methods: A retrospective review of all patients with localized prostate adenocarcinoma treated with IMRT was conducted. Eligible patients had a minimum of 2 years of follow-up (including early deaths). Median follow-up was 59.3 (18.6-90.1) months. Patients received 5 field IMRT delivering either 75.6 or 77.4 Gy to the prostate and 50.4 Gy to the seminal vesicles. Transabdominal ultrasound was used to reduce risk for geographic miss. Biochemical control rates were calculated according to the American Society for Therapeutic Radiology and Oncology (ASTRO)-Phoenix consensus definition. Risk groups were designated on the basis of pretreatment PSA level 10 ng/mL or less, Stage T1-2 and Gleason Score #6. Depending on the number of risk factors, patients were classified as either low risk, intermediate risk or high risk. Modified RTOG scales were used to define toxicity. Results: Two hundred seventy-one patients were identified that had a minimum of 2 years of follow-up. 83% received 75.6 Gy and 15% received 77.4 Gy. Patient characteristics were: clinical Stage T2a or less, 201 pts (74.2%), T2b or higher, 70 pts (25.3%); Gleason Score \7, 119 pts (43.9%), 7-10 152 pts (56.1%); PSA \10 ng/mL 209 pts (77.1%), 10-20 44 pts (16.2%), .20 18 pts (6.6%). 35% of patients received hormonal therapy as part of initial treatment 11.8%. 2.2%, 4.1% developed biochemical recurrence, local recurrence and distant recurrence, respectively. By risk groups, the 3 and 5 year biochemical control rates were as follows: Low risk (96 pts): 95.8%, 91.5%; intermediate risk (128 pts): 95.6%, 89.2%; high risk (46 pts): 87.0%, 74.9% (p = 0.0239 log-rank). Univariate analysis found that only clinical stage was prognostic in all patients for biochemical control (p = 0.0006).
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2348
One Size Doesn’t Fit All: The Value of Adaptive Radiotherapy (ART) Planning Methods using Daily Image Guidance in Bladder Radiotherapy (RT)
S. Lalondrelle1, V. N. Hansen1, H. McNair1, R. Huddart2, A. Horwich2, D. Dearnaley2, V. Khoo3 1 3
Royal Marsden NHS Foundation Trust, Sutton, United Kingdom, 2Institute of Cancer Research, Sutton, United Kingdom, Royal Marsden NHS Foundation Trust, London, United Kingdom
Purpose/Objective(s): To determine whether adapting treatment plans using a plan selection method based on individual bladder filling patterns (A-POLO, adaptive-predictive organ localization) or using a composite volume (CV) technique provides greater improvement in accuracy during a radical course of bladder RT. Materials/Methods: A post void CT was used to define the clinical target volume, CTV1, for the whole bladder with 1.5 cm isotropic margins to generate the planning target volume, PTV1. During 32 fractions, a daily preRT cone beam CT (CBCT) was taken and retrospectively assessed. A need for ART was defined as displacement of the CBCT bladder contour (CTVcb) to within 5 mm of PTV1 in any direction on any occasion. A-POLO methodology: Additional CT planning scans were performed at 15 and 30 minutes (CT2, 3) post void to document individual patterns of bladder filling and organ motion and used to generate a library of patient-specific volumes (PTV2, 3) by adding 1.5 cm margins to CTV2, 3. From the start of RT, for each fraction needing ART the most appropriate PTV for each day was chosen from the patient’s library (i.e., PTV1, 2 or 3). CV methodology: A further CTV (CTV4) was created using CTV1 and CTVcb from Days 1-4 of treatment to define the maximum excursions of the bladder with isotropic margins of 5mm to form PTV4. This method was assessed from Day 5 onwards. The methods were compared for correction of geographic miss overall and individually. Results: The 108 RT fractions in 5 patients were assessed. Mean (range) PTV1, 2, 3 and 4 was 411.57 cc (334-511), 462 cc (360564), 482 cc (393-570) and 323 cc (285-394). During RT the mean PTVcb was 234cc (135-558) with mean interfraction (IF) translations of 0.4 cm (-1.6 to 3.7) cranially and 0.3 cm (-0.85 to 3.25) anteriorly. Overall 57% (range, 4-96%) of fractions needed ART in 100% of patients with up to 35% of PTVcb excluded. Using the A-POLO method 79% were corrected, 53% using the CV method. For adapted fractions where the PTVcb was not entirely covered by either model A-POLO left a smaller mean residual volume untreated, 4% vs. 9.1%. The mean CTVcb-selected PTV margin was .1cm (range, 1-1.5) in all dimensions with APOLO and \0.95 cm (range, 0.6-0.95) aside for cranially (1.4cm) using CV. Individually, 3 patients benefited most from an A-POLO method, 1 patient from a CV method, 1 benefited equally with either method. Conclusions: If variation in bladder size and shape is unpredictable, all patients could benefit from frequent image guidance and ART. Using a plan selection method may provide greater accuracy but requires daily imaging and intervention. The CV method results in smaller treatment volumes but does not model for large variations. A-POLO could be optimized by using anisotropic margins. On-going work will define these benefits. Author Disclosure: S. Lalondrelle, None; V.N. Hansen, None; H. McNair, None; R. Huddart, None; A. Horwich, None; D. Dearnaley, None; V. Khoo, None.
2349
Analysis of Biochemical Control, Prognostic Factors and Toxicities in Patients Treated with Intensity Modulated Radiotherapy for Localized Prostate Cancer with Longer Follow-up
S. A. Vora, W. W. Wong, S. E. Schild, G. A. Ezzell Mayo Clinic Arizona, Scottsdale, AZ Purpose/Objective(s): To review biochemical control rates, prognostic factors and toxicities (acute and chronic) for patients treated with intensity-modulated radiation therapy (IMRT). Materials/Methods: A retrospective review of all patients with localized prostate adenocarcinoma treated with IMRT was conducted. Eligible patients had a minimum of 2 years of follow-up (including early deaths). Median follow-up was 59.3 (18.6-90.1) months. Patients received 5 field IMRT delivering either 75.6 or 77.4 Gy to the prostate and 50.4 Gy to the seminal vesicles. Transabdominal ultrasound was used to reduce risk for geographic miss. Biochemical control rates were calculated according to the American Society for Therapeutic Radiology and Oncology (ASTRO)-Phoenix consensus definition. Risk groups were designated on the basis of pretreatment PSA level 10 ng/mL or less, Stage T1-2 and Gleason Score #6. Depending on the number of risk factors, patients were classified as either low risk, intermediate risk or high risk. Modified RTOG scales were used to define toxicity. Results: Two hundred seventy-one patients were identified that had a minimum of 2 years of follow-up. 83% received 75.6 Gy and 15% received 77.4 Gy. Patient characteristics were: clinical Stage T2a or less, 201 pts (74.2%), T2b or higher, 70 pts (25.3%); Gleason Score \7, 119 pts (43.9%), 7-10 152 pts (56.1%); PSA \10 ng/mL 209 pts (77.1%), 10-20 44 pts (16.2%), .20 18 pts (6.6%). 35% of patients received hormonal therapy as part of initial treatment 11.8%. 2.2%, 4.1% developed biochemical recurrence, local recurrence and distant recurrence, respectively. By risk groups, the 3 and 5 year biochemical control rates were as follows: Low risk (96 pts): 95.8%, 91.5%; intermediate risk (128 pts): 95.6%, 89.2%; high risk (46 pts): 87.0%, 74.9% (p = 0.0239 log-rank). Univariate analysis found that only clinical stage was prognostic in all patients for biochemical control (p = 0.0006).
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