Efficacy and prognosis of CT-guided of 125I radioactive seeds implantation brachytherapy as salvage treatment for recurrent nasopharyngeal carcinoma after external beam radiotherapy--A long-term experience at a single institution

Background: To assess the efficacy and prognosis of computed tomography (CT)-guided 125I radioactive seeds implantation brachytherapy (RSI-BT) for recurrent nasopharyngeal carcinoma (NPC) after external beam radiotherapy (EBRT). Methods: Thirty-one patients with recurrent NPC (forty-one lesions) after EBRT from February 2003 to January 2019 were enrolled in this retrospective study. The work-follow of CT-guidance RSI-BT was: indication selection, patient set-up and immobilization on CT couch, CT-simulation, preoperative planning, prescription doses (PD) definition of 110-160Gy, seed implantation, postoperative dosimetric evaluation and postoperative follow-up. Median radioactivity of RSI was 0.43 (range 0.22-0.79, average 0.61) mCi. Median actuarial number of 125I seeds was 24 (range 3-83, average 37). Median value of post-operative D90 was 118.5 (range 62.4-246, average 136.2) Gy. Local control (LC) and overall survival (OS) were investigated for their relationship with the prognosis. The adverse events were evaluated by the Radiation Therapy Oncology Group (RTOG) classification criteria. Results: Median follow-up was 41.9 (range 2.1-60.2, average 44.1) months. Median LC was 35.8 (range 2.1-60.2, average 34.9) months. LC at 1-, 3- and 5-year was 71.3%, 41.9% and 27.9%, respectively. Median OS was 22.6 (range 2.1~60.2, average 27.1) months. OS at 1-, 3- and 5-years was 57.7%, 23.8% and 11.9%, respectively. Univariate analysis suggested that sex (P=0.037) and frequency of previous EBRT (P=0.001) were prognostic factors influencing LC. Moreover, univariate analysis also suggested that frequency of previous EBRT (P=0.012) was prognostic factors influencing OS. Prevalence of side effects (≥grade 3) was 6.5%. Conclusion: 125I RSI-BT was a safe and feasible salvage treatment for recurrent NPC after EBRT. Key words: recurrent nasopharyngeal carcinoma; External beam radiotherapy; 125I seed implantation brachytherapy; overall survival; local control; side effects.

Accuracy evaluation of a 3D-printed individual template for needle guidance in head and neck brachytherapy

To transfer the preplan for the head and neck brachytherapy to the clinical implantation procedure, a preplan-based 3D-printed individual template for needle insertion guidance had previously been designed and used. The accuracy of needle insertion using this kind template was assessed in vivo. In the study, 25 patients with head and neck tumors were implanted with 125I radioactive seeds under the guidance of the 3D-printed individual template. Patients were divided into four groups based on the site of needle insertion: the parotid and masseter region group (nine patients); the maxillary and paranasal region group (eight patients); the submandibular and upper neck area group (five patients); and the retromandibular region group (six patients). The distance and angular deviations between the preplanned and placed needles were compared, and the complications and time required for needle insertion were assessed. The mean entrance point distance deviation for all 619 needles was 1.18 ± 0.81 mm, varying from 0.857 ± 0.545 to 1.930 ± 0.843 mm at different sites. The mean angular deviation was 2.08 ± 1.07 degrees, varying from 1.85 ± 0.93 to 2.73 ± 1.18 degrees at different sites. All needles were manually inserted to their preplanned positions in a single attempt, and the mean time to insert one needle was 7.5 s. No anatomical complications related to inaccurately placed implants were observed. Using the 3D-printed individual template for the implantation of 125I radioactive seeds in the head and neck region can accurately transfer a CT-based preplan to the brachytherapy needle insertion procedure. Moreover, the addition of individual template guidance can reduce the time required for implantation and minimize the damage to normal tissues.