Safety and efficacy of self-expandable metallic stent combined with 125I brachytherapy for the treatment of malignant obstructive jaundice

Currently, few data are available comparing CT-guided intratumoral 125I seed implantation and intraluminal 125I seed strand insertion combined with stents for the treatment of MOJ [12,13,14, 17]. Therefore, this research compared the clinical outcomes of patients who had stents insertion with seed strand placement or CT-guided 125I seed implantation to those who had stents insertion alone. The results showed that SEMS combined with 125I brachytherapy may help to maintain stent patency and prolong overall survival. Moreover, no significant difference was found between CT-guided 125I seed implantation with SEMS and 125I seed strand insertion with SEMS in stent patency and overall survival.

Generally, the placement of uncovered metallic stents can rapidly reduce jaundice and improve patients’ quality of life. SEMS has been recognized as one of the primary treatments for MOJ cases. Unfortunately, stent restenosis owing to invasive tumor growth, inflammation, and tissue hyperplasia has been reported as a nonnegligible limitation of uncovered SEMS [18, 19]. Although covered stents are designed to avoid the above problem, higher stent migration rates were reported compared to uncovered stents. Moreover, the covering membrane may block collateral bile ducts, resulting in acute cholecystitis, pancreatitis, and other complications [20,21,22]. Therefore, an efficient technique to not only inhibit tumor ingrowth physically like covered stents but also induce tumor regression is highly desired.

A series of clinical investigations have demonstrated that 125I brachytherapy is effective in treating malignant tumors [9,10,11]. Compared with traditional external radiotherapy, 125I seed brachytherapy can deliver a higher effective dose of radiation into the tumor with a limited influence on surrounding normal tissues and adjacent organs. Additionally, 125I seeds can continuously release X- and γ-rays onto the tumor cells, efficiently decreasing cell proliferation and increasing cell sensitivity to radiation [23]. Furthermore, as a form of conformal radiotherapy, 125I brachytherapy is associated with minimal treatment errors owing to patient mobility.

Chen et al. [24] showed that intraluminal brachytherapy using an 125I seed strand fixed in a drainage catheter through a stent was a safe and effective therapy for MOJ patients, but no conclusions regarding patient survival were reported. Guo et al. [25] first reported the use of a SEMS loaded with 125I seeds to treat advanced esophageal cancer. Zhu et al. [10] studied the application of irradiation biliary stents loaded with 125I seeds in the treatment of malignant biliary obstruction. It demonstrated that 125I seed-loaded biliary stents significantly prolonged stent patency and patients’ survival compared to the control group. Several more recent clinical studies on the combination of 125I seeds and SEMS have been attempted, which also demonstrated that the combined technique can offer significantly better stent patency and patients’ survival than stent alone [11, 14, 26, 27]. The current study demonstrated that the median duration of primary stent patency was significantly longer in the brachytherapy group compared with the control group (289 vs. 88 days, respectively, p =0.001). In this study, the median overall survival was considerably better in the brachytherapy group than in the control group (221 vs. 78 days, respectively, p =0.001). This study also confirmed that the combination of SEMS with 125I brachytherapy was a favorable prognostic factor associated with patient survival. Meanwhile, the TBIL and DBIL dropped dramatically one month after the procedure in both groups. The above results seemingly suggest that the 125I brachytherapy group had longer stent patency and patient survival. It demonstrated that additive 125I brachytherapy would considerably alleviate compression or invasion of tumors in patients.

However, in subgroup analysis, no significant difference between CT-guided 125I seed implantation and 125I seed strand insertion was found in stent patency and median overall survival (all p >0.05). The small sample size and difference in patient selection might explain part of this result. In the present study, we found that both two 125I brachytherapy techniques were safe and effective in treating MOJ, and the choice of technique depended on the nature and location of the tumor. The 125I seed strand insertion was preferred for the invasive growth tumor along the bile duct wall, especially when the common bile duct was invaded. As most such tumors had short diameters, implanting seeds directly into the tumor was difficult. While the combined therapy of SEMS with 125I seed strand insertion presented various advantages for such advanced tumors invading the bile duct wall. First, the delivery of the 125I seed strand through the outer cannula could reduce the potentially adverse events related to multiple direct puncturing of the tumor for radioactive seed implantation. Second, because the seeds were linearly sealed into a catheter to construct a seed strand and fixed steadily between the stent and biliary wall, the seed dislodgment probability after implantation could be decreased. Third, the 125I seed strand was accurately attached in the diseased section by the force of SEMS, which can effectively inhibit tumor cell invasion and epithelial cell hyperplasia around the bile duct wall, thereby delaying the recurrence of stent stenosis. On the other hand, for tumors that invaded the right and left intrahepatic bile duct or distal from the bile duct, CT-guided 125I seed implantation was considered to be the first choice. First, due to the short radiation radius of the 125I seeds, the intraluminal seed strand is difficult to thoroughly eliminate the lesion distal to the bile duct, while intratumoral 125I seed implantation can mainly cover the whole lesion under CT guidance, compensating for the lack of total dose distribution away from the seed strand. Moreover, the brachytherapy of the 125I seed strand was effective for about six months, and thereafter, those patients could not receive the re-implantation of fresh 125I seed strand to maintain the brachytherapy. In contrast, CT-guided 125I seed implantation showed superiority in the replacement of 125I seeds when appropriate, thus maintaining long-term brachytherapy to the whole lesion, reducing the lateral pressure of the tumor on the bile duct, delaying the invasion of the bile duct wall, and ensuring the patency of the biliary stent for a certain period. Furthermore, CT scans also can help ensure that the preoperative TPS strategy is precisely performed, resulting in better local control and patient survival.

In the current study, the incidence of complications is consistent with the reported studies [14, 28]. No major complications were founded in the two groups. The majority of complications were manageable with conservative therapy. Patients who received stent placement coupled with seed strand or with CT-guided 125I seed implantation had no more complications than stent alone, demonstrating that 125I seed combined brachytherapy is safe.

Limitations

The present research still has several limitations. First, this was a retrospective study with a limited sample size, which reduced the statistical power of the conclusion. Second, indicators like tumor markers were not collected dynamically, therefore the therapy effect on tumor biological behavior was not assessed. Third, this study failed to assess tumor response to 125I seed brachytherapy due to the difficulty in evaluating the lesions with the Response evaluation criteria in solid tumors (RECIST) criteria [29].

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