The purpose of this study is to verify the accuracy, short-term efficacy and side effects of 3D printing coplanar template combined with CT-guided I-125 seeds implantation in the treatment of malignant tumors of the head and neck.

Iodine-125 seeds Implantation (RISI) for the treatment of tumors, mainly with the help of imaging guidance, the radioactive I-125 seeds radioactive source is directly implanted into the tumor tissue, and the purpose of killing tumor cells is achieved through the continuous release of radiation by radionuclide. At present, it has been clinically used in the local treatment of tumors in head and neck, chest, abdomen, pelvis, spine, columns and limbs. The main technical difficulties in implementing RISI lies in the complexity of operation and the control of operation quality.In the era of unarmed puncture, the quality of operation is difficult to guarantee, and the therapeutic effect is quite different.In 2015, our unit carried out RISI technology under the guidance of 3D model plates, which significantly improved the treatment accuracy of RISI.

The current 3D printing templates are divided into two types: non-coplanar template (3D-PNCT) and coplanar template (3D-PCT). In clinical practice, due to the complex technical requirements, high production cost and long printing time of non-coplanar mold board, a considerable number of patients can be well treated with coplanar template.Compared with the non-coplanar individualized template, the coplanar template has the advantages of accurate needle path control, rapid needle path adjustment, convenient real-time optimization, batch production without waiting for template printing time, and the operation is easy to process, easy for doctors to grasp quickly, the cost is lower than non-coplanar template, and easy to carry out at the grass-roots level. However, most of the existing clinical application data of the template come from the non-coplanar template, and the dosimetry, needle path error and clinical effect of particle implantation guided by the coplanar template are still lack of research. Therefore, this study intends to explore the coplanar template technology and analyze the safety and effectiveness of 3D printing coplanar template combined with CT-guided I-125 seeds implantation in the treatment of head and neck malignant tumors.

The purpose of this study is to verify the accuracy, short-term efficacy and side effects of 3D printing coplanar template combined with CT-guided I-125 seeds implantation in the treatment of malignant tumors of the head and neck.

Inclusion Criteria:

• the age is 18-80 years old;
• the pathological diagnosis is clear, patients with local recurrence / metastasis of head and neck tumor after operation or external radiotherapy;
• the tumor diameter ≤ 5cm, the number of lesions ≤ 3;
• there is a suitable puncture path, and the target dose of pre can reach the prescribed dose;
• KPS ≥ 70 points, the expected survival time is more than 3 months;
• patients have signed a consent form for I-125 seeds implantation therapy;
• patients have signed the consent form of knowing emotions to participate in this observational study;

Exclusion Criteria:

• coagulation dysfunction;
• tumor surface rupture, or tumor memory liquefied and necrotic in a large range, with poor expected particle distribution;
• severe underlying diseases, resulting in unsafe completion of I-125 seeds implantation therapy, including active infections requiring drug treatment;
• mental abnormalities affecting cognitive ability;
• poor compliance and inability to complete treatment;
• those who were considered unsuitable to participate in this clinical trial;

The sample size was calculated by One-Sample Log-rank Tests in PASS 15 software. Class I error probability (α) = 0. 05; class II error probability (β) = 0. 2, that is, power = 1-β = 0. 8. According to the experience and data of the center, it is assumed that the local control index can be more than doubled by reducing RISI, that is, Hazard Rates113 (M1:M0) = 2:1. Finally the sample size was calculated to be 25 cases, and the sample size of was estimated to be 30 cases considering the 20% loss of follow-up rate.