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Cosmetic Outcome after Accelerated Partial Breast Irradiation: Correlation with Dose and the Volume of Skin Treated
Proceedings of the 52nd Annual ASTRO Meeting volume receiving dose 45 Gy, 20 Gy, and 5 Gy in RA plans were 3.2 ± 0.89, 9.31 ± 2.6, and 24.02 ± 6.42 but for F-IMRT plans dose were 6.49 ± 1.16, 10.42 ± 2.28, and 14.47 ± 1.87, respectively (p \ 0.001). Conclusions: RapidArc plans produced good conformity and homogeneity index with excellent dose coverage. RapidArc reduced the OAR volume receiving high doses (V45 and V20). F-IMRT scored in low dose volume (V5) which was more in RA plans due to multiple beams entries. RA plans provided reduced heart dose and improved lung sparing, at the cost of increased low dose volume in contra lateral breast & lung as compared to F-IMRT. Author Disclosure: S. Thirumalai Swamy, None; V. Subramanian, None; M. Kathirvel, None; G. Arun, None; S. Chilukuri, None; S. Kala, None; N. Jagadeesh, None.
2049
Cosmetic Outcome after Accelerated Partial Breast Irradiation: Correlation with Dose and the Volume of Skin Treated
D. A. Todor, R. B. Vera, D. W. Arthur Medical College of Virginia, Richmond, VA Purpose/Objective(s): To identify an anatomic structure and its associated dose-volume constraints that correlate with long term cosmesis for breast cancer patients treated with adjuvant accelerated partial breast radiation (APBI) delivered with brachytherapy. Materials/Methods: A single institution retrospective review of the 129 patients, treated from 2000-2005 with APBI balloon and multicatheter brachytherapy, revealed 70 patients had dose-volume histogram (DVH) reconstruction that was electronically available. A new dermal structure, extending from the skin surface to a 5mm depth, was created for each plan. The dose rate, maximum skin surface dose, V90, V100, V150 and V200 to this dermal structure were recorded and analyzed. Clinical follow-up was scheduled at regular intervals and included history, physical exam, and mammography. Overall cosmesis was a physician-graded evaluation using the Harvard scale from grade 1 (excellent), grade 2 (good), grade 3 (fair) and grade 4 (poor). Additional toxicities, in the form of hyperpigmentation, telangectasia, and fibrosis, were graded on the RTOG scale of 0-4. These patients were further divided into two populations of acceptable cosmesis (AC) and unacceptable cosmesis (UC). The AC group included patients who had grade 1 overall cosmesis as well as patients with grade 2 overall cosmesis without documented toxicity. The UC group consisted of 5 patients with either a grade 3-4 overall cosmesis or a grade 2 overall cosmesis and documented toxicity of at least grade 1 hyperpigmentation, telangectasia, or fibrosis. Results: For the 70 patients with available DVH analysis, there was a median follow-up of 41.7 months. The AC group had a mean Dmax to the skin surface of 2.66Gy (SD = 0.47Gy), and the UC group had a mean Dmax to the skin surface of 2.98Gy (SD = 1.01Gy). Based on a statistical analysis, the maximum dose to skin surface did not discriminate between the two groups. The mean dermal V90 for the AC group was 4cc (SD = 2.6cc), and the mean dermal V90 for the UC group was 7cc (SD 2.4cc). The dermal V90 was able to distinguish between the two groups with statistical significance. Moreover, a threshold value for a dermal V90 of less than 5cc’s was associated with an excellent to good outcome. Conclusions: The current restriction limiting the Dmax at the skin surface does not appear to correlate with grade 1/grade 2 cosmesis. However, limiting the V90 to less than 5cc’s of the skin dermis was significantly correlated with a good/excellent cosmesis. Author Disclosure: D.A. Todor, None; R.B. Vera, None; D.W. Arthur, None.
2050
Dosimetric Implications of Changes in Breast and Tumor Bed Volumes between Initial Simulation and Re-simulation for Boost Treatment
M. M. Urie1, A. Stark2, J. M. Sawicka2 1
University of Massachusetts Medical School, Worcester, MA, 2UMass Memorial Medical Center, Worcester, MA
Purpose/Objective(s): To evaluate the dosimetric differences of the ipsi-lateral breast, lung, and heart in breast cancer irradiation between defining and planning the boost target volume on the initial planning CT scan or on a re-scan obtained at 40-45 Gy dose to the breast. Materials/Methods: Fifty women with breast cancer (29 right sided, 21 left sided) who had undergone lumpectomy and were CT scan planned for radiation therapy to the breast (to 50.4 Gy) had repeat CT scans just prior to beginning their boost treatments. Boost target volumes, to receive between 8 Gy and 16 Gy, were delineated on both scans. Photon boost plans (nearly all 3-field, 6MV, IMRT) were developed on both scans for the boost target volumes. The boost treatment fields from the original scan boost plan were transferred to the repeat scan and calculated; this represents what would have been treated had there not been a rescan. Changes in breast volume and boost target volumes were obtained. Dose volume histograms were used to evaluate differences in dose to the breast, ipsi-lateral lung, and heart. Results: The mean initial breast volume was 1004 cc (range, 256cc -2142cc) and the mean initial boost volume was 50.3 cc (range, 2.9 cc – 186 cc). Breast volumes on rescan averaged 908 cc with the change ranging from +1.3% to -30.5%. Boost volumes averaged 29.3 cc smaller on rescan, with a range of -0.5% to -89.5%. There was little difference in the maximum dose in the irradiated volume, averaging 67.1 Gy as treated and 67.6 Gy had there been no rescan. The volume of breast receiving various doses was less with the rescanned plans; for example at 68 Gy, 64 Gy, 60 Gy, and 56 Gy, the average difference between with and without rescan was 7.3 cc (1.1%), 40.8 cc (4.0%), 77.6 cc (6.9%) 80.3 cc (7.2%), respectively. However, there was significant variation among patients, with ranges from 0-186 cc, 0-504 cc, 46-822 cc, and 78-1060 cc at 68 Gy, 64 Gy, 60 Gy, and 56 Gy, respectively. The ipsilateral lung did receive slightly less dose with the rescan plans; the difference in volume of ipsi-lateral lung averaged 0.5% at 50 Gy, 0.1% at 40 Gy, 0.08% at 30 Gy, 0.2% at 20 Gy, and 0.6% at 10 Gy. In no case was the dose to the heart altered measurably by the difference in boost volume definition. Conclusions: Rescans of breast patients just prior to the beginning of boost treatment shows significant variability among patients as to changes in breast volume and boost target volume. On average, the rescan plans resulted in less dose to the breast tissue and ipsi-lateral lung, and no significant difference to the heart. In no case would the boost target as defined on the repeat scan have been missed if the original boost target had been treated. Author Disclosure: M.M. Urie, None; A. Stark, None; J.M. Sawicka, None.
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2049
Cosmetic Outcome after Accelerated Partial Breast Irradiation: Correlation with Dose and the Volume of Skin Treated
D. A. Todor, R. B. Vera, D. W. Arthur Medical College of Virginia, Richmond, VA Purpose/Objective(s): To identify an anatomic structure and its associated dose-volume constraints that correlate with long term cosmesis for breast cancer patients treated with adjuvant accelerated partial breast radiation (APBI) delivered with brachytherapy. Materials/Methods: A single institution retrospective review of the 129 patients, treated from 2000-2005 with APBI balloon and multicatheter brachytherapy, revealed 70 patients had dose-volume histogram (DVH) reconstruction that was electronically available. A new dermal structure, extending from the skin surface to a 5mm depth, was created for each plan. The dose rate, maximum skin surface dose, V90, V100, V150 and V200 to this dermal structure were recorded and analyzed. Clinical follow-up was scheduled at regular intervals and included history, physical exam, and mammography. Overall cosmesis was a physician-graded evaluation using the Harvard scale from grade 1 (excellent), grade 2 (good), grade 3 (fair) and grade 4 (poor). Additional toxicities, in the form of hyperpigmentation, telangectasia, and fibrosis, were graded on the RTOG scale of 0-4. These patients were further divided into two populations of acceptable cosmesis (AC) and unacceptable cosmesis (UC). The AC group included patients who had grade 1 overall cosmesis as well as patients with grade 2 overall cosmesis without documented toxicity. The UC group consisted of 5 patients with either a grade 3-4 overall cosmesis or a grade 2 overall cosmesis and documented toxicity of at least grade 1 hyperpigmentation, telangectasia, or fibrosis. Results: For the 70 patients with available DVH analysis, there was a median follow-up of 41.7 months. The AC group had a mean Dmax to the skin surface of 2.66Gy (SD = 0.47Gy), and the UC group had a mean Dmax to the skin surface of 2.98Gy (SD = 1.01Gy). Based on a statistical analysis, the maximum dose to skin surface did not discriminate between the two groups. The mean dermal V90 for the AC group was 4cc (SD = 2.6cc), and the mean dermal V90 for the UC group was 7cc (SD 2.4cc). The dermal V90 was able to distinguish between the two groups with statistical significance. Moreover, a threshold value for a dermal V90 of less than 5cc’s was associated with an excellent to good outcome. Conclusions: The current restriction limiting the Dmax at the skin surface does not appear to correlate with grade 1/grade 2 cosmesis. However, limiting the V90 to less than 5cc’s of the skin dermis was significantly correlated with a good/excellent cosmesis. Author Disclosure: D.A. Todor, None; R.B. Vera, None; D.W. Arthur, None.
2050
Dosimetric Implications of Changes in Breast and Tumor Bed Volumes between Initial Simulation and Re-simulation for Boost Treatment
M. M. Urie1, A. Stark2, J. M. Sawicka2 1
University of Massachusetts Medical School, Worcester, MA, 2UMass Memorial Medical Center, Worcester, MA
Purpose/Objective(s): To evaluate the dosimetric differences of the ipsi-lateral breast, lung, and heart in breast cancer irradiation between defining and planning the boost target volume on the initial planning CT scan or on a re-scan obtained at 40-45 Gy dose to the breast. Materials/Methods: Fifty women with breast cancer (29 right sided, 21 left sided) who had undergone lumpectomy and were CT scan planned for radiation therapy to the breast (to 50.4 Gy) had repeat CT scans just prior to beginning their boost treatments. Boost target volumes, to receive between 8 Gy and 16 Gy, were delineated on both scans. Photon boost plans (nearly all 3-field, 6MV, IMRT) were developed on both scans for the boost target volumes. The boost treatment fields from the original scan boost plan were transferred to the repeat scan and calculated; this represents what would have been treated had there not been a rescan. Changes in breast volume and boost target volumes were obtained. Dose volume histograms were used to evaluate differences in dose to the breast, ipsi-lateral lung, and heart. Results: The mean initial breast volume was 1004 cc (range, 256cc -2142cc) and the mean initial boost volume was 50.3 cc (range, 2.9 cc – 186 cc). Breast volumes on rescan averaged 908 cc with the change ranging from +1.3% to -30.5%. Boost volumes averaged 29.3 cc smaller on rescan, with a range of -0.5% to -89.5%. There was little difference in the maximum dose in the irradiated volume, averaging 67.1 Gy as treated and 67.6 Gy had there been no rescan. The volume of breast receiving various doses was less with the rescanned plans; for example at 68 Gy, 64 Gy, 60 Gy, and 56 Gy, the average difference between with and without rescan was 7.3 cc (1.1%), 40.8 cc (4.0%), 77.6 cc (6.9%) 80.3 cc (7.2%), respectively. However, there was significant variation among patients, with ranges from 0-186 cc, 0-504 cc, 46-822 cc, and 78-1060 cc at 68 Gy, 64 Gy, 60 Gy, and 56 Gy, respectively. The ipsilateral lung did receive slightly less dose with the rescan plans; the difference in volume of ipsi-lateral lung averaged 0.5% at 50 Gy, 0.1% at 40 Gy, 0.08% at 30 Gy, 0.2% at 20 Gy, and 0.6% at 10 Gy. In no case was the dose to the heart altered measurably by the difference in boost volume definition. Conclusions: Rescans of breast patients just prior to the beginning of boost treatment shows significant variability among patients as to changes in breast volume and boost target volume. On average, the rescan plans resulted in less dose to the breast tissue and ipsi-lateral lung, and no significant difference to the heart. In no case would the boost target as defined on the repeat scan have been missed if the original boost target had been treated. Author Disclosure: M.M. Urie, None; A. Stark, None; J.M. Sawicka, None.
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