Ultrasound-Guided 125I Seed Implantation in Treatment of Abdominal Wall Metastases (2025)

Abstract

Background: The treatment of abdominal wall metastasis presents a challenge, because resection can be followed by poor healing and external radiotherapy is associated with serious adverse events. This study aimed to evaluate the efficacy and safety of interstitial ¹²⁵I seed implantation under ultrasound (US) guidance for treating abdominal wall metastasis.

Materials and Methods: The cases of 21 patients with 28 abdominal wall metastases who received brachytherapy with ¹²⁵I seeds at the department from August 2010 to March 2015 were retrospectively reviewed. ¹²⁵I seeds were implanted in the abdominal wall lesions under US guidance and with the help of a treatment planning system. Follow-up was performed using computed tomography at 1 d and at 3, 6, and 12 months after implantation. The lymphocyte count before the surgery was compared with the 3-month postoperative count. The main indicators observed were changes in tumor size, side effects, and complications.

Results: All 21 patients were successfully treated with ¹²⁵I seed implantation under US guidance. The median follow-up since ¹²⁵I seed implantation was 15 months (range 6–23 months). The response rates and local tumor control after 3, 6, and 12 months were 78.6% and 89.3%, 64.3% and 85.7%, and 52.4% and 71.4%, respectively. The mean preoperative lymphocyte count was 0.262 ± 0.117 × 10⁹/L, which did not differ significantly from the postoperative count, which was 0.259 ± 0.094 × 10⁹/L (p = 0.122). Procedure-related complications included fever, bleeding, and pain, but all these were Grade 1–2. No severe side effects or complications were noted.

Conclusions: Percutaneous interstitial implantation of ¹²⁵I seeds under US guidance is safe and feasible for abdominal wall metastases. However, its long-term efficacy requires further investigation.

Introduction

Abdominal wall metastases are generally detected after laparoscopic or general surgery in patients with malignant tumors arising in the abdomen or pelvis.¹ They occur deep in the wall, and patients often have no obvious symptoms in the early stages. At present, although several therapeutic modalities, including surgery, chemotherapy, ablation,² and radiotherapy, can be used to treat local abdominal wall metastases, the treatment has not been standardized. Metastases are often resected surgically in the clinic,^1,3 but this treatment presents a challenge because the extent of resection of malignant tumor metastases in the abdominal wall should include 2–3 cm margins, making subsequent wound healing difficult.^4–6 In addition, not all tumors are resectable. External radiotherapy is an alternative, but the associated serious adverse events such as nausea, vomiting, diarrhea, and chronic enteritis limit its use.⁷ Ultrasound (US)-guided local ablation is a minimally invasive treatment option and includes radiofrequency ablation, cryoablation, and microwave ablation (MWA).⁸ High-frequency US ablation has yielded good curative effects in the treatment of abdominal metastatic tumors.⁹ MWA may be a feasible, safe, and effective treatment for abdominal wall metastases,² but local ablation is expensive.

Radioactive ¹²⁵I seed brachytherapy is a low-risk and minimally invasive therapy that has been widely applied to various malignant tumors.^10,11 To the authors' knowledge, no study has evaluated the effectiveness and safety of percutaneous interstitial implantation with ¹²⁵I seeds under US guidance for abdominal wall metastases. Thus, the purpose of this study was to assess the effectiveness and safety of this procedure and to identify possible complications in the short and medium terms.

Materials and Methods

Results

The patients were followed up for a mean of 15 months (range 6–23 months). The mean number of seeds implanted in this cohort was 24 ± 19.4 (range 8–69). One patient died of multiple metastases from pancreatic cancer 9 months after treatment, 6 died of disease progression, and the remaining 14 patients survived at least 5 years. No patients died of abdominal wall metastases.

The mean preoperative lymphocyte count was 0.262 ± 0.117 × 10⁹/L, and it did not differ significantly from the postoperative count, which was 0.259 ± 0.094 × 10⁹/L (p = 0.122).

The patients showed good response rates of 78.6%, 64.3%, and 52.4% in the 3, 6, and 12 months after treatment, respectively. The patients showed local tumor control of 89.3%, 85.7%, and 71.4% in the 3, 6, and 12 months after treatment, respectively. Tumor response at 3 months, which was demonstrated on CT assessment, revealed CR in 8 cases (Fig. 1D), PR in 14 cases, SD in 3 cases, and PD in 3 cases. At 6 months, revealed CR in 10 cases, PR in 8 cases, SD in 6 cases, and PD in 4 cases. In post-treatment 12 months, revealed CR in 3 cases, PR in 8 cases, SD in 4 cases, and PD in 6 cases (Table 3).

Four patients experienced procedure-related fever. Grade 1 (38°C–39°C) in 3 patients and Grade 2 (39.1°C) in 1 patient. Three patients experienced mild bleeding, which resolved after spontaneous remission without treatment. Three patients experienced pain but were not administered analgesics. One patient suffered diarrhea, probably because the lesions were very close to the intestinal tract. No other serious complications, such as intestinal fistula or radiation-related enteritis, occurred during the follow-up period (Table 4).

Discussion

Radiotherapy for malignant tumors includes external radiation and brachytherapy. Clinically, traditional external beam radiotherapy is riddled with problems, such as a high whole-body dose accompanying a low local dose, serious radiation damage, easy-to-produce hot spots, visceral damage, and poor repeatability.¹¹ In ¹²⁵I seed brachytherapy, radioactive particles are implanted under US or CT guidance, with the aim of damaging cancer cells to the maximum extent with continuous low-energy rays (initial dose rate: 0.07–0.09 Gy/h). Whitmore used ¹²⁵I brachytherapy to treat prostate cancer for the first time in 1972.¹⁴ In the United States, ¹²⁵I brachytherapy is considered a first-line treatment for early prostate cancer.^15,16 In China, ¹²⁵I brachytherapy has been used to treat pancreatic, liver, and head and neck cancers.^17–22 The clinical use of ¹²⁵I brachytherapy has shown curative effects.^23–26

The indications for ¹²⁵I brachytherapy include radical treatment of solid tumors, eradication of solid tumor tissue remaining after surgery, treatment of inoperable metastases, and palliation of primary tumors. Contraindications include ineligibility for radiation therapy (e.g., in the case of blood cancer) and anesthesia, widely dispersed lesions, an active or hemorrhaging ulcer and necrosis at the tumor site, and skin ulcers at the puncture site.¹² Overall, the advantage of ¹²⁵I seed implantation is obvious.

During ¹²⁵I seed implantation, the greatest difficulty is ensuring that the radiation emitted completely covers the PTV. US guidance was used, which enables real-time monitoring of the implantation process, adjustments to the position of the puncture needle, and is not injurious to the patient and operator, in addition to preoperative planning with TPS streamlines treatment. All patients need CT verification of the seed position on the first postoperative day to allow adjustments in seed placement. In this study, 7 cases required adjustments to implantation. US real-time monitoring can guarantee proper additional implantation by experienced operators.

The patients showed a good response rate of 78.6%, 64.3%, and 52.4% and local tumor control of 89.3%, 85.7%, and 71.4% in the 3, 6, and 12 months after treatment, respectively. The maximum curative effect was achieved maximum with 3 months postoperatively, which may be associated with the half-life of the radioactive particles. The characteristics of ¹²⁵I include a low initial dose rate, a physical half-life of about 60.1 d, and an average energy of 28 keV.

Treatment of abdominal wall metastases is closely related to the prognosis and quality of life of patients.^7,25 It is well known that brachytherapy and local ablation are minimally invasive treatments that maintain good quality of life.^2,25 Wound healing after tumor resection is difficult and local ablation is expensive. Abdominal wall metastases located in a superficial position are good candidates for US-guided brachytherapy. Research has confirmed that the tumor-destructive effects in metastases by ¹²⁵I seeds last about 280 d, which is equivalent to four to five times its half-life.²⁷ This study confirmed that seed implantation achieves a higher local dose with better efficacy and fewer treatment-related complications. No serious complications occurred during intra- and postoperative follow-up.

This study has some limitations: (1) the number of cases was small, and the follow-up period was relatively short; (2) ¹²⁵I brachytherapy was not compared with other treatment methods; (3) TPS was not used to match real-time US, which should be addressed in the future; and (4) the efficacy of US-guided implantation is closely related to the operator's experience.

In conclusion, US-guided ¹²⁵I particle implantation is a safe and effective method to treat abdominal wall metastases and has certain value for clinical applications, although its long-term effects need further investigation.

Acknowledgments

This study was funded by the National Natural Science Foundation of China (81471683). The authors thank Libby Cone, MD, MA, from Liwen Bianji, Edanz Group China (www.liwenbianji.cn/ac) for editing a draft of this article.

Authors' Contributions

L.H. was in charge of research design, acquisition, analysis of data, and drafting and approval of the article. L.J. did the interpretation and analysis of data, critical revision, and approval of the submitted and final versions. Z.Y. did the critical revision and approval of the article. H.Z. and L.P. also did the research design and approval of article. L.F. did the acquisition of data and approval of the article. Y.X. was responsible for the research design, communication with all other authors, and approval of the submitted and final versions.

Disclosure Statement

No competing financial interests exist.

References