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Late rectal bleeding: fitting clinical data with different NTCP models
S392
I. J. Radiation Oncology
● Biology ● Physics
Volume 57, Number 2, Supplement, 2003
Conclusions: Hormonal therapy did not have an independent effect on the risk of early rectal and bladder complications after 3D CRT. Radiation dose and the inclusion of lymph nodes on PTV were the only significant factors affecting early toxicity on MVA.
2082
Late Rectal Bleeding: Fitting Clinical Data with Different NTCP Models 1
T. Rancati, G. Gagliardi,3 G.M. Cattaneo,2 C. Cozzarini,2 G. Fellin,4 G. Girelli,5 G. Sanguineti,6 V. Vavassori,7 R. Valdagni,8 C. Fiorino2 1 University of Milan, Milan, Italy, 2Medical Physics and Radiotherapy, H. S. Raffaele, Milan, Italy, 3Hospital Physics, Karolinska Hospital, Stockholm, Sweden, 4Radiotherapy, Ospedale S. Chiara, Trento, Italy, 5Radiotherapy, Azienda Ospedaliera ASL 9, Ivrea, Italy, 6Radiotherapy, UTMB, Galveston, TX, 7Medical Physics and Radiotherapy, Ospedale di Circolo, Varese, Italy, 8Radiotherapy, Clinica Pio X, Milan, Italy Purpose/Objective: Fit different complication probability (NTCP) models to clinical outcome on late rectal bleeding (lrb) after radiotherapy (RT) for prostate cancer. Materials/Methods: Within the Italian AIRO working group on prostate RT, rectal dose-volume histograms (DVH) and clinical data of 547 patients (pts) pooled from five institutions were analyzed. All pts were treated in supine position with 3 or 4-field techniques: 123 pts received ICRU dose between 64 and 70 Gy, 255 pts between 70 and 74 Gy and 169 pts between 74 and 79.2 Gy; 457/547 pts were treated with conformal RT and 203/547 underwent radical prostatectomy before RT. Rectum (including filling) was contoured from anal verge up to sigmoid by an observer from each institution; inter-institute variability in contouring rectum and in calculating DVHs was previously investigated and found acceptable. Minimum follow-up was 18 months. Pts were considered as bleeders if showing grade 2/3 lrb (slightly modified RTOG/EORTC scoring system) within 18 months after the end of RT. Four NTCP models were considered: (a) Lyman-Kutcher-Burman (LKB), (b) the Lyman model with DVH reduced to the equivalent uniform dose (LEUD), (c) logistic with DVH reduced to EUD (LOGEUD) and (d) relative seriality (RS). The parameters for the different models were fit to patient data using a maximum likelihood analysis. The 68% confidence intervals (CI) of each parameter were also derived. Results: Forty-six of 547 pts experienced grade 2/3 lrb: 38/46 developed lrb within 18 months and were then considered as bleeders. All models well describe the clinical outcome. The risk of lrb is a smooth function of EUD (calculated from DVH using n⫽0.23 (CI 0.05), best fit result). Using LEUD the relationship between EUD and NTCP can be described with a TD50 of 81.9 Gy (CI 1.8 Gy) and a steepness parameter m of 0.19 (CI 0.01); when using LOGEUD, TD50 is 82.2 Gy and k is 7.85. Best fit parameters for LKB and RS are n⫽0.23 m⫽0.19 TD50⫽81.9 Gy and s⫽0.49 gamma⫽1.69 TD50⫽83.1 Gy respectively. Qualitative (see fig: LEUD model) as well as quantitative comparisons (chi-squared p⫽0.005) show that models fit the observed lrb rates very well. The results found in the overall population are substantially confirmed in the subgroup of radically treated pts (LEUD: n⫽0.24 m⫽0.14 TD50⫽75.8 Gy). Conclusions: Different NTCP models fit quite accurately the considered clinical data. The results are consistent with a rectum “less serial” than previously reported investigations. EUD may be considered robust and simple to calculate parameter correlated with the risk of lrb.
2083
Brachytherapy Versus Brachytherapy Plus External Beam Radiation for Prostate Cancer: A Comparison of Urinary Symptoms and Quality of Life
M. Jain,1 R.G. Stock,1 N.N. Stone2 Radiation Oncology, Mount Sinai Medical Center, New York, NY, 2Urology, Mount Sinai Medical Center, New York, NY
1
Purpose/Objective: To compare post treatment urinary symptoms and quality of life in patients treated with interstitial seed implant alone and seed implant in combination with external beam radiation. Materials/Methods: Seven hundred forty-five patients who were treated between 1/1/1997 and 12/31/2001 were retrospectively identified. The time frame was chosen for consistency in technique and availability of dosimetry. Only those patients who received a dose of 45 Gy in 1.8 Gy fractions via external beam were included in the analysis. Data from 595 seed implant
I. J. Radiation Oncology
● Biology ● Physics
Volume 57, Number 2, Supplement, 2003
Conclusions: Hormonal therapy did not have an independent effect on the risk of early rectal and bladder complications after 3D CRT. Radiation dose and the inclusion of lymph nodes on PTV were the only significant factors affecting early toxicity on MVA.
2082
Late Rectal Bleeding: Fitting Clinical Data with Different NTCP Models 1
T. Rancati, G. Gagliardi,3 G.M. Cattaneo,2 C. Cozzarini,2 G. Fellin,4 G. Girelli,5 G. Sanguineti,6 V. Vavassori,7 R. Valdagni,8 C. Fiorino2 1 University of Milan, Milan, Italy, 2Medical Physics and Radiotherapy, H. S. Raffaele, Milan, Italy, 3Hospital Physics, Karolinska Hospital, Stockholm, Sweden, 4Radiotherapy, Ospedale S. Chiara, Trento, Italy, 5Radiotherapy, Azienda Ospedaliera ASL 9, Ivrea, Italy, 6Radiotherapy, UTMB, Galveston, TX, 7Medical Physics and Radiotherapy, Ospedale di Circolo, Varese, Italy, 8Radiotherapy, Clinica Pio X, Milan, Italy Purpose/Objective: Fit different complication probability (NTCP) models to clinical outcome on late rectal bleeding (lrb) after radiotherapy (RT) for prostate cancer. Materials/Methods: Within the Italian AIRO working group on prostate RT, rectal dose-volume histograms (DVH) and clinical data of 547 patients (pts) pooled from five institutions were analyzed. All pts were treated in supine position with 3 or 4-field techniques: 123 pts received ICRU dose between 64 and 70 Gy, 255 pts between 70 and 74 Gy and 169 pts between 74 and 79.2 Gy; 457/547 pts were treated with conformal RT and 203/547 underwent radical prostatectomy before RT. Rectum (including filling) was contoured from anal verge up to sigmoid by an observer from each institution; inter-institute variability in contouring rectum and in calculating DVHs was previously investigated and found acceptable. Minimum follow-up was 18 months. Pts were considered as bleeders if showing grade 2/3 lrb (slightly modified RTOG/EORTC scoring system) within 18 months after the end of RT. Four NTCP models were considered: (a) Lyman-Kutcher-Burman (LKB), (b) the Lyman model with DVH reduced to the equivalent uniform dose (LEUD), (c) logistic with DVH reduced to EUD (LOGEUD) and (d) relative seriality (RS). The parameters for the different models were fit to patient data using a maximum likelihood analysis. The 68% confidence intervals (CI) of each parameter were also derived. Results: Forty-six of 547 pts experienced grade 2/3 lrb: 38/46 developed lrb within 18 months and were then considered as bleeders. All models well describe the clinical outcome. The risk of lrb is a smooth function of EUD (calculated from DVH using n⫽0.23 (CI 0.05), best fit result). Using LEUD the relationship between EUD and NTCP can be described with a TD50 of 81.9 Gy (CI 1.8 Gy) and a steepness parameter m of 0.19 (CI 0.01); when using LOGEUD, TD50 is 82.2 Gy and k is 7.85. Best fit parameters for LKB and RS are n⫽0.23 m⫽0.19 TD50⫽81.9 Gy and s⫽0.49 gamma⫽1.69 TD50⫽83.1 Gy respectively. Qualitative (see fig: LEUD model) as well as quantitative comparisons (chi-squared p⫽0.005) show that models fit the observed lrb rates very well. The results found in the overall population are substantially confirmed in the subgroup of radically treated pts (LEUD: n⫽0.24 m⫽0.14 TD50⫽75.8 Gy). Conclusions: Different NTCP models fit quite accurately the considered clinical data. The results are consistent with a rectum “less serial” than previously reported investigations. EUD may be considered robust and simple to calculate parameter correlated with the risk of lrb.
2083
Brachytherapy Versus Brachytherapy Plus External Beam Radiation for Prostate Cancer: A Comparison of Urinary Symptoms and Quality of Life
M. Jain,1 R.G. Stock,1 N.N. Stone2 Radiation Oncology, Mount Sinai Medical Center, New York, NY, 2Urology, Mount Sinai Medical Center, New York, NY
1
Purpose/Objective: To compare post treatment urinary symptoms and quality of life in patients treated with interstitial seed implant alone and seed implant in combination with external beam radiation. Materials/Methods: Seven hundred forty-five patients who were treated between 1/1/1997 and 12/31/2001 were retrospectively identified. The time frame was chosen for consistency in technique and availability of dosimetry. Only those patients who received a dose of 45 Gy in 1.8 Gy fractions via external beam were included in the analysis. Data from 595 seed implant