The efficacy and dosimetry analysis of CT-guided 125I seed implantation assisted with 3D-printing non-co-planar template in locally recurrent rectal cancer

Abstract

Background

Locally recurrent rectal cancer (LRRC) after surgery or external beam radiotherapy (EBRT) is a serious challenge for which no standard treatment is defined. In the present study, we investigated the feasibility of computed tomography (CT)-guided radioactive ¹²⁵I seed (RIS) implantation assisted with three-dimensional printing non-coplanar template (3D-PNCT) in LRRC patients who previously received surgery or EBRT.

Methods

Sixty-six patients with LRRC treated by CT-guided RIS implantation in our institute from December 2015 to May 2019 were included. The treatment procedure included: preoperative CT localization, planning design, the printing of 3D individualized template, CT-guided RIS implantation assisted with 3D-PNCT, and postoperative dose evaluation. Therapeutic outcomes including local control (LC) and overall survival (OS) were retrospectively evaluated, as well as side effects.

Results

All the patients had previously received surgery or EBRT. The median follow-up time was 12.2 (range, 2.5–35.9) months. The median radioactive activity of a single RIS was 0.6 (range, 0.43–0.72) mCi. The median number of RIS was 60, ranging from 10 to 175. The dosimetric parameters included D90 (140.7 ± 33.1) Gy, D100 (90.3 ± 138.6) Gy, and V100 (91.0 ± 13.3) %. Pain relief was achieved in 85.1% (40/47) of patients. Besides, 9.1% (6/66) of patients had severe side effects (≥grade 3), including perianal skin ulcer in 1 case, fistula, radiation proctitis, and intestinal obstruction each in two cases. Median OS time was 14.7 (95% confidence interval (CI): 13.0–16.3) months, and median LC time was 12.2 (95% CI: 9.1–15.2) months. Univariate analysis revealed that when D90 > 130 Gy or D100 > 55 Gy or V100 > 90%, the LC time was remarkably prolonged. However, none of the parameters significantly affected OS.

Conclusions

CT-guided RIS implantation assisted with 3D-PNCT is an effective and safe salvage treatment strategy for patients with LRRC after EBRT or surgery. D90, D100, and V100 can be used as prognostic predictors.

Trial registration

NCT03890926.