Breast Cancer

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TU_2_3333 - Comparison of Conventional Dynamic IMRT Plan Versus Target Segmented Plan in Irradiation of Postmastectomy Patients

Tuesday, October 23
2:45 PM - 4:15 PM
Location: Innovation Hub, Exhibit Hall 3

Comparison of Conventional Dynamic IMRT Plan Versus Target Segmented Plan in Irradiation of Postmastectomy Patients
J. Hu1, G. Han1, X. Xu2, W. GE2, C. Ruan3, S. Chang4, A. Zhang1, and Q. Song2; 1Department of radiation oncology,Renmin hospital of WuHan University, Wu Han, China, 2Department of oncology,Renmin hospital of WuHan University, Wu Han, China, 3Department of Radiation Oncology,Renmin Hospital of Wuhan University, Wuhan, China, 4Department of Radiation Oncology, Renmin Hospital of Wuhan University, Wuhan, China

Purpose/Objective(s): This study aims to compare the dosimetric differences between Target Segmented Plan (TSP) and Conventional Dynamic IMRT (CD-IMRT) for irradiation of postmastectomy patients, with or without the involvement of internal mammary nodes (IMN).

Materials/Methods: This study enrolled twenty-two consecutive breast cancer patients (12 left-sided and 10 right-sided) underwent radical mastectomy. The clinical target volume (CTV) included the ipsilateral chest wall, supra/infra-clavicular, partial axillary in high risk, and IMN (if metastatic or if the tumor was localized in the internal quadrants). The prescription dose of CTV was 50Gy delivered in 25 fractions, 5 days per week. The organs at risk (OARs) near the targets, including bilateral lungs, heart, contralateral breast, ipsilateral humeral head and spinal cord, were contoured as well. In CD-IMRT method, the CTV was treated as a whole; on the contrary, in TSP method, the CTV was divided into separate regions, i.e., supra/infra-clavicular region,chest wall region,external region and internal mammary region. The planning target volume (PTV) was generated by adding a 5-10mm uniform margin around the CTV, and was limited to the skin surface. Two kinds of treatment plan were created for each patient using a treatment planning system with the same dose optimization objectives. The dose-volume histograms were compared for the PTVs and OARs.

Results: All plans achieved the dose prescription and dose criteria. TSP and CD-IMRT plans showed similar PTV dose homogeneity index, V50Gy and D2%, but, TSP provided a better dose conformity index for all patients and a smaller D98% for the left-sided patients compared with CD-IMRT (P<0.05). The doses to all OARs excluding the ipsilateral lung were similar. Compared with CD-IMRT plans, the V5Gy,V10Gy,V20Gy and Dmean for the ipsilateral lung were significantly reduced with TSP (P<0.05). For left-sided patients, The V5Gy,V10Gy,V20Gy and Dmean for the ipsilateral lung were 50.03±6.81%, 34.04±4.42%, 26.59±3.47% and 14.44±1.47Gy by TSP, 74.49±10.21%, 46.09±11.17%, 27.89±3.90% and 17.49±2.26Gy by CD-IMRT, respectively. And for right-sided patients, the same dose parameters for the ipsilateral lung were 49.33±1.81%, 32.41±2.71%, 24.76±3.11% and 13.86±1.23Gy by TSP, 70.37±4.91%, 42.54±6.39%, 26.29±2.38% and 16.55±1.29Gy by CD-IMRT, respectively.

Conclusion: For patients with radical mastectomy, TSP is not only dosimetrically feasible as CD-IMRT treatment technique, but also could effectively reduce the irradiation volume of the ipsilateral lungs in the low dose area with minimum adverse dosimetric impact on the treatment targets and other OARs.

Author Disclosure: J. Hu: None. G. Han: None. C. Ruan: None. S. Chang: None.

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