Published online Dec 14, 2018. doi: 10.3748/wjg.v24.i46.5280
Peer-review started: September 6, 2018
First decision: October 4, 2018
Revised: October 27, 2018
Accepted: November 9, 2018
Article in press: November 9, 2018
Published online: December 14, 2018
Patients with advanced pancreatic cancer frequently suffer from intractable pain secondary to tumor perineural invasion. This pain can be relieved by traditional external radiotherapy but with significant systemic side effects. To reduce these side effects, in previous studies, radioactive iodine-125 seeds acting as the source of radiation were implanted in pancreatic lesions under computed tomography (CT) guidance, and this approach demonstrated efficacy for local tumor control and pain relief. However, the special location of the pancreas and fragile adjacent organ increase implantation difficulty and lead to inconsistent dosimetric parameters before and after implantation.
3D-printed template is a new iodine-125 seed implantation guidance tool, which can improve implantation accuracy and radiotherapy dosimeters in superficial organs. However, few studies have sufficient information on its application in profound organs, especially the pancreas. As the pancreatic dosimetric parameters are unsatisfactory by using the traditional free hand way, 3D-printed template might be an applicable guidance tool.
The main objective of our study was to evaluate the efficacy and safety of this new guidance tool in the treatment of advanced pancreatic cancer. The preliminary results demonstrated that the procedure is safe and the brachytherapy dosimeters are better in the 3D-printed template group.
In this retrospective study, 25 patients with advanced unresectable pancreatic carcinoma were treated with iodine-125 seed implantation. Of these, 12 implantations were assisted by a 3D-printed coplanar template (group A), and the remaining 13 implantations were performed without template guidance and selected as a control group (group B). For group A, the template was made of polymethyl methacrylate (PMMA). Its shape and size were designed and printed based on the entry point and puncture angle. All procedures were performed under CT guidance. The postoperative CT images were sent to TPS to calculate the D90, V90, V100, and V150. For both groups, the dosimetric data were collected and compared. Standard chemotherapy was performed in all patients 1 week after the implantation.
Iodine-125 seeds were successfully inserted into all pancreatic tumors in groups A and B. For group A, the median pre- and postoperative D90 values were 155.32 ± 8.05 Gy and 154.82 ± 16.43 Gy, respectively; the difference between the values was minimal and not statistically significant (P = 0.91). The postoperative V90, V100, and V150 values were 94.64% ± 2.35%, 91.05% ± 4.06%, and 64.54% ± 13.40%, respectively. Among these, V90 and V100 were slightly lower than planned, and the reasons for this might include the following: (1) altered location and morphology of the pancreatic lesion due to the presence of implantation needles; and (2) the presence of an intratumor necrosis area into which the iodine-125 seeds might migrate due to gravity. Nevertheless, the position of the iodine-125 seeds changed only slightly, and the average postoperative V100 was still greater than 90% and likely did not influence prognosis. The dose of the 3D coplanar template guide group exceeded that of the group B, and the difference was statistically significant (P = 0.00). No major procedure-related complications were observed. For group A, mild hemorrhage was observed in 1 patient with a peritoneal local hematoma duo to mesenteric vein injury.
According to our study, 3D-printed coplanar template-assisted iodine-125 seed implantation therapy appears to be safe and effective and may improve the implantation accuracy and similarity between the postoperative dosimetric parameters and treatment planning values. 3D-printed coplanar template may be an ideal assistive tool for the iodine-125 seed implantation not only in superficial organs but also in profound organs, e.g., the pancreas.
The key limitations of our study include the small sample size and short follow-up period. However, the endpoints of the study included dosimeter and safety results. The long-term curative effect and complications associated with this approach will be evaluated in a future case-control prospective study.