Patients with dependent cardiac implantable electronic devices (CIED) should avoid proton therapy to thorax due to high risk of malfunction resulted from secondary neutron production by proton beam. However, there was limited literature to evaluate the neutron dose on CIED in proton therapy for head and neck cancer. This study aimed to measure the doses of scattered photon and neutron on the surface site of CIED in scanning proton therapy to right neck.
A treatment planning of scanning proton therapy using rightanterior-
oblique field and right-posterior-oblique field to treat right side head and neck cancer with 200cGy per fraction was adopted. On the bilateral infraclavicular surface areas of RANDO phantom, the Electronic Personal Dosimeters (DMC 3000 with Neutron Module) were set to simulate the ipsilateral and contralateral sites of CIED. We recorded the values of H10-
gamma and H10-neutron detected by the dosimeters in proton therapy.
The mean doses of H10-gamma and H10-neutron were 0.033 mSv and 0.530 mSv per fraction at left infraclavicular area and 0.024 mSv and 0.210 mSv per fraction at right infraclavicular area. Notably, both doses of scattered photon and neutron at left side were larger than those at right side despite the proton therapy to right neck.
The doses of scattered photon and neutron at bilateral infraclavicular areas were low; however, the doses at left side were unexpectedly larger than those at right side. The electrocardiogram monitoring during proton therapy and program analyzing after treatment should not be completely waived.

PTCOG58