We use cookies necessary to giving you a better online experience. By using our website you consent to all cookies in accordance with our Privacy Policy.
Yes, I accept
Menu
Search Opener

Session Item

Sunday
August 02
14:15 - 16:15
Skin workshop
Workshop
00:00 - 00:00
Internal Mammary Lymph Node Volumes: What Radiation dose is received with modified wide tangents?
PO-0925

Abstract

Internal Mammary Lymph Node Volumes: What Radiation dose is received with modified wide tangents?
Authors: UJAIMI|, Reem(1)*[rkujaimi@kau.edu.sa];Attar|, Mohammed(1);Awad|, Nisreen(2);Hasan|, Zakaria(3);Al-Khateeb|, Shyma(4);Abbas|, Noura(4);Baageel|, Wejdan(4);Khayyat|, Salma(4);
(1)Faculty of Medicine - King Abdulaziz University, Radiotherapy section- department of Radiology, Jeddah, Saudi Arabia;(2)King Abdulaziz University Hospital, Radiotherapy section- department of Radiology, Jeddah, Saudi Arabia;(3)King Faisal Specialist Hospital and Research Center, Biomedical Physics, Jeddah, Saudi Arabia;(4)Faculty of applied medical Sciences - King Abdulaziz University, Diagnostic radiography technology, Jeddah, Saudi Arabia;
Show Affiliations
Purpose or Objective

There is a growing interest in radiating the internal mammary nodes (IM) in the context of adjuvant radiotherapy in breast cancer. There has been variation in defining its CTV and the acceptable coverage. Clear definition is necessary particularly when using modified treatment techniques. This paper ought to estimate the dose delivered to an institutionally defined IM CTV using the standard modified wide tangent technique (MWT).

Material and Methods

Ten patients were randomly selected. The IM vessels in the first three intercostal spaces were contoured. Five mm were added, and trimmed from anatomical boundaries, to create CTV. Subsequently, three PTVs were created .PTV1 was created by adding 5 mm uniform expansion around CTV. To create PTV2, PTV 1 was trimmed from the lung and heart. PTV 3 was created by expanding 5 mm around the IM vessels. A plan optimization target volume was generated by adding 1 cm around the vessels following the MA 20 protocol for CT based planning. Apart from the later volume, the planner was blinded to all other volumes. . The treatment planning was forward using 3-4 fields with the aim to cover the target volumes by 90% to 95%  of the dose whilst keeping V20 of the lung below 35% and the V25 of the heart below 10% with as minimum mean heart dose as possible . Two modified wide tangential fields were used to cover the internal mammary lymph nodes and breast or chest wall and one anterior field, with or without a posterior field for the supraclavicular lymph nodes. A dose of 50Gy/25 fractions was prescribed at the isocenter. The heart and lungs were contoured using RTOG consensus guidelines. DVH curves for normal tissue were generated.

Results

Six left and four right sided patients were included. Nine and one patients underwent mastectomy and lumpectomy, respectively. The mean percentage of the volume that received 95% (V95) ±SD was: IM vessel (V95) = 85.491 ±14.059, CTV (V95) = 78.727 ±14.289, PTV 1 (V95) = 65.879 ±11.987, PTV 2 (V95) = 76.047 ±12.311, PTV 3 (V95) = 70 ±12.836. The mean percentage of the volume that received 90% (V90) ±SD were: IM vessel (V 90) = 91.866±10.867, CTV (V90) = 86.038 ±12.788, PTV 1 (V90) = 75.341 ±11.553, PTV 2 (V90) = 81.246% ±11.609, PTV 3 (V90) = 81.312 ±11.697. The mean heart V25 was 0.037±0.04 and 5.5±3.4 for right and left sided patients, respectively. The mean of the mean heart dose for the left sided patients was 4.5± 1.8 .The mean lung V20 was 35.148±0.39 and 34.314±1.17 for right and left sided patients, respectively.

Conclusion

Apart from the IM vessels, the MWT does not cover the IM volumes. If the indication to treat the IM is strong and particularly in the case of positive IM, accurate contouring and contour based planning as well as advanced techniques should be used.