Comparison of Photon-electron and Photon Radiotherapyfor Supraclavicular Lymph Nodes of Mastectomy Patientswith Left-sided Breast Cancer

ABSTRACT

The aim of radiotherapy is to deliver the highest possible radiation dose to the tumor and the lowest radiation to normal tissues surroundingthe tumor. In the present study, lymph nodes of the supraclavicular region were treated using two therapeutic techniques,namely photon technique (PT) and combinatory photon-electron technique (CPET). We recruited 50 patients with local lymph nodemetastasis. The photon energies were 6-15 MV. Furthermore, the electron beam energy was 18 MeV in CPET. The study findingsrevealed that the mean delivered dose to target volume was 41.12 ± 2.98Gy for PT and 44.56 ± 1.90Gy for CPET. The percentage ofthe target volume irradiated to 90% of the prescribed dose (V90) was calculated as 74.61% ± 9.30% and 82.06% ± 9.70% for PT andCPET, respectively. The mean dose delivered to the heart and lungs was not significantly different between the two groups. Furthermore,the maximum doses delivered to the spinal cord were 12.55Gy in PT and 8.89Gy in CPET. The mean doses delivered to thethyroid gland were 39.26 and 34.89Gy in PT and CPET. According to the study results, the maximum doses delivered to the spinalcord, head of the humerus bone, and thyroid were reduced significantly as measured the CPET technique. In contrast, no significantdifference was observed regarding the dose delivered to the heart and lung. The dose delivered to the supraclavicular region determinedby the CPET was significantly augmented. Furthermore, the coverage of the tumor mass was optimized using the new method.