- Email: [email protected]
Interfraction Uncertainties in Multifraction Gynecologic Interstitial Brachytherapy (MGIB)
Poster Viewing Abstracts S757
Volume 84 Number 3S Supplement 2012 Poster Viewing Abstract 3432; Table ROC analysis (AUC Z Area under ROC curves; P value corresponds to testing that AUC s 0.5)
Whole group (N Z 147)
Patients with a tumor in either of the upper lobes (N Z 96)
Patients with a tumor in middle or either of the lower lobes (N Z 51)
Radiation dose-volume parameters
AUC
P
AUC
P
AUC
P
MLD V5 V10 V20 V30 V40 V50
0.678 0.598 0.607 0.661 0.667 0.677 0.651
0.029 0.227 0.187 0.048 0.040 0.030 0.064
0.859 0.709 0.743 0.850 0.865 0.854 0.849
0.003 0.087 0.047 0.004 0.003 0.004 0.004
0.365 0.372 0.323 0.337 0.419 0.512 0.538
0.331 0.254 0.114 0.147 0.468 0.917 0.736
lobes, and 6.3% for the group with tumor in either of the upper lobes (P Z 0.064). ROC analysis indicated that areas for predictive parameters MLD, V20, V30, V40, and V50 varied significantly between the two patient groups as shown in the Table. The parameters in the LKB model were found to be n Z 0.87 0.40, m Z 0.27 0.10, and TD50 (1) Z 29.5 8.0 Gy. Conclusions: The incidence of SARP depends on the dose-volume parameters MLD, V20, V30, V40, and V50, and on the tumor location. The SARP rate for the patient group with tumor in the middle or lower lobes was higher than that for the group with tumor in the upper lobes. The predictive powers of the dose-volume parameters for SARP differed between the two patient groups. Author Disclosure: J. Wang: None. Y. Bao: None. T. Zhuang: None. Z. He: None. L. Zhang: None. A. Tai: None. P. Prior: None. M. Chen: None. X. Li: None.
3433 Interfraction Uncertainties in Multifraction Gynecologic Interstitial Brachytherapy (MGIB) A. Damato,1 K. Townamchai,1 A. Kovacs,1 R. Cormack,1,2 and A. Viswanathan1,2; 1Dana Farber Cancer Institute/Brigham and Women’s Hospital, Boston, MA, 2Harvard Medical School, Boston, MA Purpose/Objective: Inter-fraction anatomy changes and catheter displacements can potentially impact the delivered dosimetry of an MGIB treatment. We assessed the variation in metrics of the rectum (R), bladder (B), sigmoid (S) and HR-CTV (H) during MGIB. Material/Methods: Records of 19 patients recently treated in our clinic with MGIB were analyzed within an IRB-approved protocol. Contours for R, B, S were drawn on two CT scans: one acquired immediately (D0_S) and one 48-72 hours (D2_S) after implantation. To minimize contouring uncertainty, H was drawn on the D0_S only. A clinical plan (P_0) was obtained on D0_S. A plan (P_2) was obtained by replicating P_0 on D2_S. D2cc per fraction for R, B, and S was calculated for P_0 and P_2. To evaluate variation in H dose, D0_S and D2_S were registered based on a rigid fusion of the pubic symphysis and cranial/caudal (CC) catheter shifts were recorded. A modified plan (P_0_M) was obtained by modifying P_0 so that catheters were adjusted to reflect the observed CC shifts. D2cc per fraction for R, B, and S, V100 and D90 for H were calculated on P_0_M. Results: Results are summarized in the Table. Comparing P_0 with P_2, 12 patients experienced an increase in R D2cc (rg 0.0 - 2.01 Gy); 6
Poster Viewing Abstract 3433; Table
P_0 P_2 P_0_M
patients experienced a decrease (rg 0.02 - 0.42 Gy); 1 patient did not have a R. 9 patients experienced an increase in B D2cc (rg 0.07 - 1.83 Gy); 10 patients experienced a decrease (rg 0.02 - 1.25 Gy). 6 patients experienced an increase in S D2cc (rg 0.06 - 1.57 Gy); 13 patients experienced a decrease (rg 0.01 - 1.85 Gy). Comparing P_0 with P_0_M, small changes were observed for R, B and S D2cc, suggesting poor correlation with CC catheter shift. For H, 6 patients experienced an increase in V100 (rg 0.05% - 1.24%). Thirteen patients experienced a decrease in V100 (rg 0.02% - 8.3%). D_0 and D_0_M V100 were 100% for 1 patient. 8 patients experienced an increase in D90 (rg 0.03 6.67 %); 12 patients experienced a decrease ranging (rg 0.22 to 19.73%). No patient in our cohort experienced a decrease in D90 from >100% to <100%. A sharper degradation of D90 and V100 is observed as the fraction of CC shifts per implant exceeds 80%. Conclusion: Clinically relevant increases in R, B and S D2cc were observed in some cases, and are likely due to changes in anatomy. Degradation of H metrics was dependent on the fraction of CC shifts observed for each patient, with a sizable amount of degradation visible only for patients experiencing CC shifts involving most of the catheters in the implant. Author Disclosure: A. Damato: None. K. Townamchai: None. A. Kovacs: None. R. Cormack: None. A. Viswanathan: None.
3434 Potential Gender Differences in a Normal Tissue Complication Probability Model for Heart Toxicity During Radiation Therapy for Esophageal Cancer M. Snyder,1 J. Burmeister,1 M. Joiner,1 J. Meyer,2 L. Tait,1 S. Cohen,2 E. McSpadden,1 and A. Konski1; 1Wayne State University, Detroit, MI, 2 Fox Chase Cancer Center, Philadelphia, PA Purpose/Objective(s): In order to determine tolerance doses for cardiac toxicity during radiation therapy for esophageal cancer, the Lyman Kutcher Burman (LKB) model of Normal Tissue Complication Probability (NTCP) was fit to clinical data. Materials/Methods: Toxicity data from 127 patients treated between June 2002 and April 2011 was were used to derive LKB parameters n, m, and TD50. Two models were fit to the data: 1) A model for all patients described by a single TD50 value for then entire patient population, and 2) A subset model whereby separate TD50 values were allowed for male and female patients. Fitting was performed using maximum likelihood estimation. 68% confidence intervals for the NTCP curves were estimated using the profile likelihood method. The significance of allowing subsetspecific TD50 values was evaluated through a likelihood ratio test. Results: The LKB parameters for cardiac toxicity in the entire population were n Z 15.9 (0.37 - 139.5), m Z 0.64 (0.35 - 1.09) and TD50 Z 41.4Gy (24.3 - 54.7). The strange n value suggests that allowing only a single TD50 value in the LKB fit for this these data results in a very broad set of possible solutions, and makes a conventional physical interpretation of the n parameter difficult. In contrast, the subset model of cardiac toxicity where male and female patients were allowed separate TD50 values produced LKB parameters of n Z 0.58 (0.20 - 6.8), m Z 0.39 (0.23 0.63), male-TD50 Z 55.3Gy (47.4 - 71.6) and female-TD50 Z 36.6Gy (27.6 - 43.2). Allowing gender-specific TD50 values in the subset model produces an n value that can more easily be interpreted as the standard volume effect, seemingly indicative of a more “realistic” fit to the data. The likelihood ratio test for the subset model with respect to the original model produced a p-value Z 0.004, indicating a better fit by the subset model.
Summary of results
R D2cc (Gy)
B D2cc (Gy)
S D2cc (Gy)
H V100 (%)
H D90 (%)
2.871.07 (1.20 - 5.17) 3.161.49 (1.21 - 7.17) 2.801.14 (1.15 - 5.10)
3.341.45 (0.96 - 6.41) 3.441.63 (0.84 - 6.53) 3.451.48 (0.95 - 6.47)
1.560.97 (0.20 - 3.18) 1.481.30 (0.26 - 4.75) 1.581.00 (0.20 - 3.3)
89.312.5 (62.5- 100) N/A 87.713.6 (57 - 100)
106.826.2 (54.1 - 142.9) N/A 103.116.6 (52.1 - 144.2)
Volume 84 Number 3S Supplement 2012 Poster Viewing Abstract 3432; Table ROC analysis (AUC Z Area under ROC curves; P value corresponds to testing that AUC s 0.5)
Whole group (N Z 147)
Patients with a tumor in either of the upper lobes (N Z 96)
Patients with a tumor in middle or either of the lower lobes (N Z 51)
Radiation dose-volume parameters
AUC
P
AUC
P
AUC
P
MLD V5 V10 V20 V30 V40 V50
0.678 0.598 0.607 0.661 0.667 0.677 0.651
0.029 0.227 0.187 0.048 0.040 0.030 0.064
0.859 0.709 0.743 0.850 0.865 0.854 0.849
0.003 0.087 0.047 0.004 0.003 0.004 0.004
0.365 0.372 0.323 0.337 0.419 0.512 0.538
0.331 0.254 0.114 0.147 0.468 0.917 0.736
lobes, and 6.3% for the group with tumor in either of the upper lobes (P Z 0.064). ROC analysis indicated that areas for predictive parameters MLD, V20, V30, V40, and V50 varied significantly between the two patient groups as shown in the Table. The parameters in the LKB model were found to be n Z 0.87 0.40, m Z 0.27 0.10, and TD50 (1) Z 29.5 8.0 Gy. Conclusions: The incidence of SARP depends on the dose-volume parameters MLD, V20, V30, V40, and V50, and on the tumor location. The SARP rate for the patient group with tumor in the middle or lower lobes was higher than that for the group with tumor in the upper lobes. The predictive powers of the dose-volume parameters for SARP differed between the two patient groups. Author Disclosure: J. Wang: None. Y. Bao: None. T. Zhuang: None. Z. He: None. L. Zhang: None. A. Tai: None. P. Prior: None. M. Chen: None. X. Li: None.
3433 Interfraction Uncertainties in Multifraction Gynecologic Interstitial Brachytherapy (MGIB) A. Damato,1 K. Townamchai,1 A. Kovacs,1 R. Cormack,1,2 and A. Viswanathan1,2; 1Dana Farber Cancer Institute/Brigham and Women’s Hospital, Boston, MA, 2Harvard Medical School, Boston, MA Purpose/Objective: Inter-fraction anatomy changes and catheter displacements can potentially impact the delivered dosimetry of an MGIB treatment. We assessed the variation in metrics of the rectum (R), bladder (B), sigmoid (S) and HR-CTV (H) during MGIB. Material/Methods: Records of 19 patients recently treated in our clinic with MGIB were analyzed within an IRB-approved protocol. Contours for R, B, S were drawn on two CT scans: one acquired immediately (D0_S) and one 48-72 hours (D2_S) after implantation. To minimize contouring uncertainty, H was drawn on the D0_S only. A clinical plan (P_0) was obtained on D0_S. A plan (P_2) was obtained by replicating P_0 on D2_S. D2cc per fraction for R, B, and S was calculated for P_0 and P_2. To evaluate variation in H dose, D0_S and D2_S were registered based on a rigid fusion of the pubic symphysis and cranial/caudal (CC) catheter shifts were recorded. A modified plan (P_0_M) was obtained by modifying P_0 so that catheters were adjusted to reflect the observed CC shifts. D2cc per fraction for R, B, and S, V100 and D90 for H were calculated on P_0_M. Results: Results are summarized in the Table. Comparing P_0 with P_2, 12 patients experienced an increase in R D2cc (rg 0.0 - 2.01 Gy); 6
Poster Viewing Abstract 3433; Table
P_0 P_2 P_0_M
patients experienced a decrease (rg 0.02 - 0.42 Gy); 1 patient did not have a R. 9 patients experienced an increase in B D2cc (rg 0.07 - 1.83 Gy); 10 patients experienced a decrease (rg 0.02 - 1.25 Gy). 6 patients experienced an increase in S D2cc (rg 0.06 - 1.57 Gy); 13 patients experienced a decrease (rg 0.01 - 1.85 Gy). Comparing P_0 with P_0_M, small changes were observed for R, B and S D2cc, suggesting poor correlation with CC catheter shift. For H, 6 patients experienced an increase in V100 (rg 0.05% - 1.24%). Thirteen patients experienced a decrease in V100 (rg 0.02% - 8.3%). D_0 and D_0_M V100 were 100% for 1 patient. 8 patients experienced an increase in D90 (rg 0.03 6.67 %); 12 patients experienced a decrease ranging (rg 0.22 to 19.73%). No patient in our cohort experienced a decrease in D90 from >100% to <100%. A sharper degradation of D90 and V100 is observed as the fraction of CC shifts per implant exceeds 80%. Conclusion: Clinically relevant increases in R, B and S D2cc were observed in some cases, and are likely due to changes in anatomy. Degradation of H metrics was dependent on the fraction of CC shifts observed for each patient, with a sizable amount of degradation visible only for patients experiencing CC shifts involving most of the catheters in the implant. Author Disclosure: A. Damato: None. K. Townamchai: None. A. Kovacs: None. R. Cormack: None. A. Viswanathan: None.
3434 Potential Gender Differences in a Normal Tissue Complication Probability Model for Heart Toxicity During Radiation Therapy for Esophageal Cancer M. Snyder,1 J. Burmeister,1 M. Joiner,1 J. Meyer,2 L. Tait,1 S. Cohen,2 E. McSpadden,1 and A. Konski1; 1Wayne State University, Detroit, MI, 2 Fox Chase Cancer Center, Philadelphia, PA Purpose/Objective(s): In order to determine tolerance doses for cardiac toxicity during radiation therapy for esophageal cancer, the Lyman Kutcher Burman (LKB) model of Normal Tissue Complication Probability (NTCP) was fit to clinical data. Materials/Methods: Toxicity data from 127 patients treated between June 2002 and April 2011 was were used to derive LKB parameters n, m, and TD50. Two models were fit to the data: 1) A model for all patients described by a single TD50 value for then entire patient population, and 2) A subset model whereby separate TD50 values were allowed for male and female patients. Fitting was performed using maximum likelihood estimation. 68% confidence intervals for the NTCP curves were estimated using the profile likelihood method. The significance of allowing subsetspecific TD50 values was evaluated through a likelihood ratio test. Results: The LKB parameters for cardiac toxicity in the entire population were n Z 15.9 (0.37 - 139.5), m Z 0.64 (0.35 - 1.09) and TD50 Z 41.4Gy (24.3 - 54.7). The strange n value suggests that allowing only a single TD50 value in the LKB fit for this these data results in a very broad set of possible solutions, and makes a conventional physical interpretation of the n parameter difficult. In contrast, the subset model of cardiac toxicity where male and female patients were allowed separate TD50 values produced LKB parameters of n Z 0.58 (0.20 - 6.8), m Z 0.39 (0.23 0.63), male-TD50 Z 55.3Gy (47.4 - 71.6) and female-TD50 Z 36.6Gy (27.6 - 43.2). Allowing gender-specific TD50 values in the subset model produces an n value that can more easily be interpreted as the standard volume effect, seemingly indicative of a more “realistic” fit to the data. The likelihood ratio test for the subset model with respect to the original model produced a p-value Z 0.004, indicating a better fit by the subset model.
Summary of results
R D2cc (Gy)
B D2cc (Gy)
S D2cc (Gy)
H V100 (%)
H D90 (%)
2.871.07 (1.20 - 5.17) 3.161.49 (1.21 - 7.17) 2.801.14 (1.15 - 5.10)
3.341.45 (0.96 - 6.41) 3.441.63 (0.84 - 6.53) 3.451.48 (0.95 - 6.47)
1.560.97 (0.20 - 3.18) 1.481.30 (0.26 - 4.75) 1.581.00 (0.20 - 3.3)
89.312.5 (62.5- 100) N/A 87.713.6 (57 - 100)
106.826.2 (54.1 - 142.9) N/A 103.116.6 (52.1 - 144.2)