- Email: [email protected]
Optimizing Dosimetry for Hypofractionated Breast Patients Treated Prone
Volume 93 Number 3S Supplement 2015 heart (D0.1, D1, and D10), and percent volume of the heart to receive 25 Gy, 20 Gy, 10 Gy, and 4 Gy (V25, V20, V10, and V4). Results: Mean heart dose was 0.75 Gy for base, 0.48 Gy for boost, and 1.20 Gy for composite plans (boost contribution was 40%). On the left, these were 1.02 Gy, 0.69 Gy, and 1.69 Gy (41%), and on the right 0.51 Gy, 0.28 Gy, and 0.76 Gy (37%), respectively. Left versus right doses were significantly different (p<0.001). Boost contribution to D0.1, D1, and D10 was 19%, 23%, and 38%. On the left, this was 15%, 18%, and 33%, and on the right 38%, 40%, and 49%, respectively. Boost contribution to V4, V10, V20, and V25 was 18%, 0%, 0%, and 0%. For V4, boost contributed 14% on the left and 34% on the right. Left lower inner quadrant boost contribution was highest at 55%, followed by left upper outer quadrant at 48%, though the number of patients was small. Conclusion: Cardiac doses from modern radiation therapy were low overall. Breast boost contributes approximately 40% of the mean heart dose, both on the left and on the right, and may be greater than 50% for left lower inner quadrant lesions. This contribution is proportionately larger in the low dose regions, particularly on the right side, likely due to bremsstrahlung radiation. Given that there is no well-established minimal safe heart dose, careful attention to boost delivery and techniques to minimize boost dose are warranted. Author Disclosure: M. Bano: None. A.P. Shah: None. P. Kelly: None. D.J. Buchholz: None. T. Dvorak: None.
2104 Long-term Results of Multicatheter Accelerated Partial-Breast Irradiation I. Zoberi1 and J. Esthappan2; 1Washington University School of Medicine Department of Radiation Oncology, St. Louis, MO, 2Washington University School of Medicine, St. Louis, MO Purpose/Objective(s): Adjuvant radiation therapy has been shown to increase local control when delivered as a part of breast conservation surgery for patients with early stage disease. In an effort to expedite radiation therapy a variety of accelerated partial breast irradiation (APBI) techniques have been developed, yet there are few reports of long term outcomes. To partially address this we reviewed our experience with APBI via a multi-catheter interstitial brachytherapy (ISI) technique for patients treated before 2005. Materials/Methods: APBI began at our institution in 2003 and for several years was exclusively done via ISI. Patients treated in our clinic from February 2003 - March 2005 were reviewed. This date range was selected to allow for a minimum potential follow up period of ten years. Selection criteria for APBI at our institution predated the ASTRO consensus statement and, as such, included patients with age greater than 40 years at diagnosis, Tis-T2 (< 3cm) disease, no nodal involvement, no metastatic disease, negative surgical margins, and who underwent breast conservation surgery. We report patient and treatment characteristics as well as localregional control and survival. Results: One hundred consecutive patients were identified. Median age at diagnosis was 61 years. Median follow-up was 9.9 years. Tumor stages were 22 Tis, 72 T1, and 6 T2. All patients with invasive disease were N0. Invasive breast cancer subtypes were 62 ER/PR+ Her2 -, 7 ER/ PR+ Her2 amplified, 1 ER/PR- Her2 amplified, 7 ER/PR/Her2-. By ASTRO APBI consensus categories: 41 were Suitable, 40 Cautionary, and 19 Unsuitable. Most patients in the Cautionary category were there due to age and/or DCIS histology while most patients in the Unsuitable category were there due to age < 50 years. ISI was performed via a free hand technique either in the operating room or via ultrasound guidance. The goal of the ISI was to encompass the surgical cavity plus a 2 cm margin. This approach used 22 catheters on average and treated a mean PTV volume of 163 dL. Mean coverage by the prescription dose of 34 Gy/10 fractions/twice daily was 95% with mean values for 1 - V150/ V100 Z 0.78, V150 Z 53 mL, and V200 Z 18 mL. Overall survival at ten years was 88% and actuarial ten-year local-regional control was 92%. There were 6 ipsilateral breast recurrences (IBR), 1 regional node
Poster Viewing Session
E43
recurrence (LN), 1 simultaneous IBR-LN recurrence, 1 LN and distant recurrence, and 1 distant recurrence. Fat necrosis was identified as a symptomatic event in 7 patients and as a mammogram-only finding in 13 patients. Fat necrosis was managed conservatively in 6 of the 7 symptomatic patients. Conclusion: Our results suggest that APBI via a multi-catheter technique in a population of predominantly Cautionary and Unsuitable patients provides durable local-regional control with limited late toxicity. Author Disclosure: I. Zoberi: None. J. Esthappan: None.
2105 Optimizing Dosimetry for Hypofractionated Breast Patients Treated Prone L. Webb and C.A. Quiet; Arizona Breast Cancer Specialists, Arizona Center for Cancer Care, Phoenix, AZ Purpose/Objective(s): To analyze dosimetric factors allowing for optimal delivery of hypofractionated radiation in patients receiving whole breast irradiation. We propose the prone position will significantly reduce normal tissue exposure in these patients. Materials/Methods: We reviewed patients evaluated for whole breast irradiation and compared dosimetric parameters allowing for hypofractionation in clinically suitable patients. 138 consecutive patients underwent CT simulation and 3D conformal dosimetry planning in both the supine and prone position. Patients were treated with the plan that had optimal dosimetric characteristics as chosen by the physician (CQ). Results: A total of 138 patients had prone and supine scans and had a target volume limited to just breast tissue. 102 patients were treated prone and 36 were treated supine. All 36 patients treated supine had better prone ipsilateral lung V20, and only 5 of the 36 had a heart V30 that was marginally worse in the prone position. 9 patients were treated supine due to patient comfort. As shown in the table below, V20 ipsilateral lung dose was significantly reduced in the prone position (p-value < 0.01) and the heart V30 in left-sided patients increased very slightly in the prone position. Average Dmax was the same for both positions. 39 patients with a Dmax less than 109% were treated using a hypofractionated dosing scheme. 34 of the 39 patients were treated in the prone position and 5 were treated supine. Of these 5 patients, 3 had optimal plans in the prone position but did not tolerate the position. For the 34 hypofractionated patients treated prone the mean ipsilateral lung V20 was 8.24% with the best supine plan, this was reduced to 1.37% when treated prone. 19 of these 34 patients were left-sided and their heart V30 was slightly higher in the prone position as compared to the supine position (0.36% v 0.16%). The table below compares the plans of all 39 hypofractionated patients in both the prone and supine positions. High energy 16 MV photons were more commonly used in the supine plans to increase the dose homogeneity (23 of 34 supine plans used 16 MV) while only 8 of 34 prone plans needed the higher energy. No difference in early toxicity was noted. Conclusion: The significant decrease in ipsilateral lung dose (p-value < 0.01) favors the use of prone positioning. As more women get treated with hypofractionated schemes, prone plans are simpler and normal tissue receives significantly less dose. More women were eligible for hypofractionation when treated in the prone position. Author Disclosure: L. Webb: None. C.A. Quiet: None.
Poster Viewing Abstracts 2105; Table 1 All patients prone Ipsilateral lung 1.99% V20 Heart V30 (only 0.38% Lt sided) Dmax 109.62%
All patients Hypofractionated Hypofractionated supine prone supine 8.78%
0.82%
8.19%
0.23%
0.31%
0.17%
109.65%
108.00%
108.10%
2104 Long-term Results of Multicatheter Accelerated Partial-Breast Irradiation I. Zoberi1 and J. Esthappan2; 1Washington University School of Medicine Department of Radiation Oncology, St. Louis, MO, 2Washington University School of Medicine, St. Louis, MO Purpose/Objective(s): Adjuvant radiation therapy has been shown to increase local control when delivered as a part of breast conservation surgery for patients with early stage disease. In an effort to expedite radiation therapy a variety of accelerated partial breast irradiation (APBI) techniques have been developed, yet there are few reports of long term outcomes. To partially address this we reviewed our experience with APBI via a multi-catheter interstitial brachytherapy (ISI) technique for patients treated before 2005. Materials/Methods: APBI began at our institution in 2003 and for several years was exclusively done via ISI. Patients treated in our clinic from February 2003 - March 2005 were reviewed. This date range was selected to allow for a minimum potential follow up period of ten years. Selection criteria for APBI at our institution predated the ASTRO consensus statement and, as such, included patients with age greater than 40 years at diagnosis, Tis-T2 (< 3cm) disease, no nodal involvement, no metastatic disease, negative surgical margins, and who underwent breast conservation surgery. We report patient and treatment characteristics as well as localregional control and survival. Results: One hundred consecutive patients were identified. Median age at diagnosis was 61 years. Median follow-up was 9.9 years. Tumor stages were 22 Tis, 72 T1, and 6 T2. All patients with invasive disease were N0. Invasive breast cancer subtypes were 62 ER/PR+ Her2 -, 7 ER/ PR+ Her2 amplified, 1 ER/PR- Her2 amplified, 7 ER/PR/Her2-. By ASTRO APBI consensus categories: 41 were Suitable, 40 Cautionary, and 19 Unsuitable. Most patients in the Cautionary category were there due to age and/or DCIS histology while most patients in the Unsuitable category were there due to age < 50 years. ISI was performed via a free hand technique either in the operating room or via ultrasound guidance. The goal of the ISI was to encompass the surgical cavity plus a 2 cm margin. This approach used 22 catheters on average and treated a mean PTV volume of 163 dL. Mean coverage by the prescription dose of 34 Gy/10 fractions/twice daily was 95% with mean values for 1 - V150/ V100 Z 0.78, V150 Z 53 mL, and V200 Z 18 mL. Overall survival at ten years was 88% and actuarial ten-year local-regional control was 92%. There were 6 ipsilateral breast recurrences (IBR), 1 regional node
Poster Viewing Session
E43
recurrence (LN), 1 simultaneous IBR-LN recurrence, 1 LN and distant recurrence, and 1 distant recurrence. Fat necrosis was identified as a symptomatic event in 7 patients and as a mammogram-only finding in 13 patients. Fat necrosis was managed conservatively in 6 of the 7 symptomatic patients. Conclusion: Our results suggest that APBI via a multi-catheter technique in a population of predominantly Cautionary and Unsuitable patients provides durable local-regional control with limited late toxicity. Author Disclosure: I. Zoberi: None. J. Esthappan: None.
2105 Optimizing Dosimetry for Hypofractionated Breast Patients Treated Prone L. Webb and C.A. Quiet; Arizona Breast Cancer Specialists, Arizona Center for Cancer Care, Phoenix, AZ Purpose/Objective(s): To analyze dosimetric factors allowing for optimal delivery of hypofractionated radiation in patients receiving whole breast irradiation. We propose the prone position will significantly reduce normal tissue exposure in these patients. Materials/Methods: We reviewed patients evaluated for whole breast irradiation and compared dosimetric parameters allowing for hypofractionation in clinically suitable patients. 138 consecutive patients underwent CT simulation and 3D conformal dosimetry planning in both the supine and prone position. Patients were treated with the plan that had optimal dosimetric characteristics as chosen by the physician (CQ). Results: A total of 138 patients had prone and supine scans and had a target volume limited to just breast tissue. 102 patients were treated prone and 36 were treated supine. All 36 patients treated supine had better prone ipsilateral lung V20, and only 5 of the 36 had a heart V30 that was marginally worse in the prone position. 9 patients were treated supine due to patient comfort. As shown in the table below, V20 ipsilateral lung dose was significantly reduced in the prone position (p-value < 0.01) and the heart V30 in left-sided patients increased very slightly in the prone position. Average Dmax was the same for both positions. 39 patients with a Dmax less than 109% were treated using a hypofractionated dosing scheme. 34 of the 39 patients were treated in the prone position and 5 were treated supine. Of these 5 patients, 3 had optimal plans in the prone position but did not tolerate the position. For the 34 hypofractionated patients treated prone the mean ipsilateral lung V20 was 8.24% with the best supine plan, this was reduced to 1.37% when treated prone. 19 of these 34 patients were left-sided and their heart V30 was slightly higher in the prone position as compared to the supine position (0.36% v 0.16%). The table below compares the plans of all 39 hypofractionated patients in both the prone and supine positions. High energy 16 MV photons were more commonly used in the supine plans to increase the dose homogeneity (23 of 34 supine plans used 16 MV) while only 8 of 34 prone plans needed the higher energy. No difference in early toxicity was noted. Conclusion: The significant decrease in ipsilateral lung dose (p-value < 0.01) favors the use of prone positioning. As more women get treated with hypofractionated schemes, prone plans are simpler and normal tissue receives significantly less dose. More women were eligible for hypofractionation when treated in the prone position. Author Disclosure: L. Webb: None. C.A. Quiet: None.
Poster Viewing Abstracts 2105; Table 1 All patients prone Ipsilateral lung 1.99% V20 Heart V30 (only 0.38% Lt sided) Dmax 109.62%
All patients Hypofractionated Hypofractionated supine prone supine 8.78%
0.82%
8.19%
0.23%
0.31%
0.17%
109.65%
108.00%
108.10%