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REVIEW ARTICLE
Year : 2018  |  Volume : 14  |  Issue : 1  |  Page : 12-17

Expert consensus statement on computed tomography-guided 125I radioactive seeds permanent interstitial brachytherapy


1 Department of Radiation Oncology, Peking University Third Hospital, Haidian, Beijing, People's Republic of China
2 Department of Thoracic Surgery, Second Hospital of Tianjin Medical University, Tianjin, People's Republic of China
3 Department of Oncology, Teng Zhou Central People's Hospital Affiliated to Jining Medical College, Teng Zhou, People's Republic of China

Date of Web Publication8-Mar-2018

Correspondence Address:
Prof. Junjie Wang
Department of Radiation Oncology, Peking University Third Hospital, Haidian, Beijing 100191
People's Republic of China
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jcrt.JCRT_888_17

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 > Abstract 

The aim of this study is to develop expert consensus statement for recommendations of patient selection criteria, prescription dose, and procedure of computed tomography (CT)-guided 125I radioactive seeds permanent interstitial brachytherapy. Members of Chinese medical association radiation oncology branch, Chinese medical association radiation therapy professional committee, Chinese cancer society minimally invasive surgery branch seed therapy group, Chinese geriatric cancer society minimally invasive surgery branch, Beijing medical association radiation oncology professional committee, China northern radioactive seeds brachytherapy group formed a committee, which consists of physician members who come from the department of radiation oncology, surgery, intervention, internal medicine, ultrasound, and nuclear medicine. The leader of the group organized experts to write the first draft based on clinical experience and literature review and then sent the draft to the commissioner for consultation, finally reached a consensus. Guidelines for patient selection criteria, prescription dose of 125I seed for different kinds of carcinomas, activity of per seed, and workflow of CT-guided permanent interstitial radioactive seed implantation (RSI) are presented in this study. The procedure of CT-guided RSI comprised eight steps: indication selection, preoperative preparation, preoperative CT simulation and position setup, preplan, intraoperative needle insertion, RSI, postoperative dosimetric evaluation, and follow-up. Patient selection criteria are developed. Guidelines for prescription dose of 125I seed for different kinds of carcinomas, activity of per seed, and workflow of CT-guided permanent interstitial RSI are provided.

Keywords: 125I seeds implantation, carcinoma, computed tomography guidance, interstitial brachytherapy


How to cite this article:
Wang J, Chai S, Zheng G, Jiang Y, Ji Z, Guo F, Zhuang H, Zhang K. Expert consensus statement on computed tomography-guided 125I radioactive seeds permanent interstitial brachytherapy. J Can Res Ther 2018;14:12-7

How to cite this URL:
Wang J, Chai S, Zheng G, Jiang Y, Ji Z, Guo F, Zhuang H, Zhang K. Expert consensus statement on computed tomography-guided 125I radioactive seeds permanent interstitial brachytherapy. J Can Res Ther [serial online] 2018 [cited 2019 Nov 15];14:12-7. Available from: http://www.cancerjournal.net/text.asp?2018/14/1/12/226770


 > Introduction Top


Permanent interstitial radioactive seed implantation (RSI) is one of the most promising treatments of brachytherapy. This therapeutic modality delivers high-radiation doses to the target volume with a sharp falloff outside the implanted volume, which kills tumor cell and spares the surrounding normal tissues.[1] Permanent interstitial RSI is a standard treatment modality for early prostate cancer. It has been popularized as a criteria strategy by several organizations in the USA: Cancer Society, Urology Society, Clinical Oncology Society, Radiation Oncology Society, Brachytherapy Society, and the National Comprehensive Cancer Network.[2],[3],[4],[5] RSI is performed under the guidance by ultrasound, computed tomography (CT), or magnetic resonance imaging (MRI) and is dependent upon surgical and interventional skills. It has been successfully applied in different malignant tumors such as pancreatic carcinoma, re-recurrent rectal cancer, and recurrent head and neck carcinoma during the past 20 years.

Chinese experts introduced CT-guidance modality into RSI in 2002. CT-guided RSI is a precise and effective method for accurate implantation of 125I seeds into tumors. CT-guided technology has the advantages of high precision and fast imaging to ensure the preciseness of seed implantation, which ensures that the seeds are placed at an optimal orientation and arrangement, and reduces the risks of seed implant treatment.[6] RSI is a type of internal radiation therapy that follows the principles of brachytherapy, including the definition of target area and organs at risk (OARs), prescription dose, and OAR dose limitation.[7] CT-guided 125I radioactive seeds permanent interstitial brachytherapy has been widely used in the treatment of many unresectable carcinomas and locally recurrent cancers such as prostate carcinoma, oral carcinoma, recurrent head and neck cancers, lung cancer, hepatocellular carcinoma, locoregional recurrent gastric cancer, liver metastasis, pancreatic cancer, NSCLC, recurrent ovarian cancer, and recurrent retroperitoneal lymph node metastases.[1],[6],[8],[9],[10],[11],[12],[13],[14],[15],[16],[17],[18],[19]

Furthermore, by combining four-dimensional (4D)-CT scans, 3D templates, bone puncture drilling, and stable needles, we overcame the problems of breathe, bone structure interference, and organ movement.[20] CT-guided RSI greatly improves the accuracy and expands the application scope of RSI. However, there are no systematic studies or reports for the guidelines and standards of CT-guided RSI at present. The consensus statement here is mainly to discuss the patient selection criteria, prescription dose of 125I seed for different kinds of carcinomas, activity of per se ed, and workflow of CT-guided permanent interstitial RSI.

Members of Chinese medical association radiation oncology branch, Chinese medical association radiation therapy professional committee, Chinese cancer society minimally invasive surgery branch seed therapy group, Chinese geriatric cancer society minimally invasive surgery branch, Beijing medical association radiation oncology professional committee, China northern radioactive-seeds brachytherapy group (CNRBG) formed a committee that consists of physician members who come from the department of radiation oncology, surgery, intervention, internal medicine, ultrasound, and nuclear medicine. The members of the committee identified the clinical indications, contraindications, prescription dose, and procedures of CT-guided 125I radioactive seeds permanent interstitial brachytherapy. The leader of the group organized experts to write the first draft based on clinical experience and extensive literature review and then sent the draft to the commissioner for consultation, finally reached a consensus. The consensus develops recommendations for clinical therapy and provides directions for further investigations.


 > The Recommended Prescription Doses for Target Volume and Dose Limitation for Organs at Risk Top


Prescription doses for target volume and evaluation parameters

The prescription doses were the efficient radiation doses that the target volume obtained according to evidence-based medicine or clinical trials to control local tumors. For the prescription doses of RSI, there was still no prospective dose gradient study except that for prostate cancer. The recommended prescription doses according to the American Brachytherapy Society for monotherapy of prostate cancer using RSI was 140–160 Gy (at least D90 [the dose that covers 90% of the prostate volume] of clinical target volume obtains the prescription doses).[4],[5] The prescription doses for other tumors were referred to mainly by international standards for prostate cancer and published articles, and 110–160 Gy was recommended.[21]

Evaluation of dosimetric parameters involved the target volume and OARs. A D90 (i.e., the dose that covered 90% of the target volume) value greater than or equal to the prescription doses was a measure of good implant quality, as are D100, V100, V150, and V200 (The conformity index, homogeneity index, and external volume index were also reliable parameters used to evaluate the quality of the treatment plan and RSI).

Dose limitation for organs at risk

Little was known about the association between most of the doses given to normal tissue and side effects when carrying out RSI. The dosimetric parameters of OARs for prostate cancer treatment included the doses that covered 30% of urethral volume (D30), D10, and D5 for the urethra and the doses that covered 2 cm 3 of the rectal volume (D2cc), D0.1cc, and V100 for the rectum. Nevertheless, the distinctive parameters for other tissues and organs should be investigated further. The recommended dose limitations for OARs were listed below and referred to reliable clinical data from prostate carcinoma.[22]

  • Rectum: D2cc <100% of the prescription doses; D0.1cc <200 Gy
  • Urethra: D10 <150% of the prescription doses; D30 <130% of the prescription doses.



 > Indications and Contraindications for Computed Tomography-Guided Radioactive Seed Implantation Top


CT scans with 5-mm thickness slice was performed 3–5 days before seed implantation to measure tumor volumes. Radiation oncologist delineated the planning target volume (PTV) and areas at risk for subclinical disease on CT scans layer by layer. The PTV defined as an extended margin of 0.5 cm to the gross tumor volume. The treatment plan was conducted with a computer treatment planning system (TPS) (B-TPS, Beijing Fei Tian Industries Inc., Beijing, China). CT-guided RSI involved transfer of CT images of tumors to B-TPS. Thus, physicians and physicists can localize the target volume and OARs, calculate the prescription doses, and designate the needle path (depth, direction, and angles): this was called “preplan,” Depending on this preplan, physicians undertook percutaneous implantation of 125I seeds into the target tumor under CT guidance. Due to interference by bone and organ movement, Chinese scholars innovatively merged bone puncture drilling, 4D-CT, and stable needles into RSI, which have improved the accuracy and safety of seed implant brachytherapy. Indications and prescription dose of 125I seed for different carcinomas are summarized in [Table 1].
Table 1: Indications, prescription dose iodine-125 seed for different kinds of carcinomas

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Radioactive seed implantation indications

  1. Recurrence after surgery and external-beam radiation therapy (EBRT), refusal of surgery and EBRT, tumor size ≤7 cm
  2. Pathologic diagnosis
  3. Applicable puncture path
  4. Without bleeding tendency or hypercoagulability
  5. Generally good physical condition (Karnofsky performance score >70)
  6. Tolerable for RSI
  7. Life expectancy ≥3 months.


Radioactive seed implantation contraindications

  1. Severe bleeding tendency with platelet count <50 × 109/L, severe dysfunction of coagulation (prothrombin time >18 s, prothrombin activity <40%). Anticoagulant therapy and/or antiplatelet drugs should be discontinued 1 week before RSI
  2. Tumor ulcers
  3. Severe diabetes mellitus
  4. Inapplicable puncture path
  5. The prescription doses of the target volume were not up to the preplan.


Relative contraindications of radioactive seed implantation

  1. Distant metastases and life expectancy ≤3 months
  2. Severe complications, infection, immune dysfunction, or renal insufficiency
  3. Patient allergic to iodinated contrast agent cannot be evaluated by enhanced CT.



 > Procedure of Computed Tomography-Guided Radioactive Seed Implantation Top


CT-guided RSI is a new minimally invasive mode of internal radiotherapy. It was operated in a standard CT room. The patient was instructed to keep in the proper position. 18-gauge interstitial needles were inserted into tumor under CT guidance in a parallel array avoiding puncture of critical structures such as large blood vessels or nearby important organs.125I seeds must be kept at least 1 cm away from critical structures and placed into tumors at a distance of 1.0 cm between the centers of any two seeds. Moreover, seed needles were placed at least 2 cm away from marginal skin to avoid severe skin reaction. The distribution and intensity of 125I seeds were verified by a CT scan according to TPS.[6],[19]

Nevertheless, strict quality control of all aspects of treatment process is crucial to ensure the success of surgery. As shown in [Figure 1], the procedure of CT-guided RSI comprised eight key steps: indication selection, preoperative preparation, preoperative CT simulation and position setup, preplan, intraoperative needle insertion, RSI, postoperative dosimetric evaluation, and follow-up. A multidisciplinary team (radiation oncologists, surgeons, interventional radiologists, physicians specializing in internal medicine and nuclear medicine, physicists, physiotherapists, anesthesiologists, nurses) was required. The detailed procedure and executor of eight steps of CT-guided RSI are shown in [Table 2].
Figure 1: Flowchart for computed tomography-guided 125I seeds implantation

Click here to view
Table 2: Work-follow for computed tomography-guided iodine-125 seeds implantation

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 > Conclusion Top


Over the past decade, 125I radioactive seeds permanent interstitial brachytherapy acknowledged as one of the most popular alternatives for the management of many unresectable carcinomas and locally recurrent cancers. This technique has some unique advantages such as minimal impairment to the lifestyle of the patient and minimal complication. As the seeds cannot be implanted accurately within tumor, the traditional technique has a high long-term failure rates. Moreover, the study results of the traditional technique of 125I radioactive seeds permanent interstitial brachytherapy are inconsistent. Chinese experts introduced CT-guidance modality into RSI in 2002. Seed positions determined the proper dose distribution, including minimum peripheral dose coverage, and the protection of surrounding tissues based on available methods for calculating optimal seed locations. CT image was used to guide the implantation of seeds needle and to adjust their position, ensuring accurate placement of seeds.[23]

Due to the improvements of 125I radioactive seeds permanent interstitial brachytherapy, CT-guided RSI improves the accuracy and homogeneity of 125I radioactive seeds implantation in nowadays.[24] Nevertheless, well-trained operation skill and attention to detail are required in the process of implantation. The patient selection criteria, prescription dose of 125I seed for different kinds of carcinomas, activity of per se ed, and workflow of CT-guided permanent interstitial 125I RSI vary widely among different radiation oncologists. There are nonclinical guidelines for CT-guided 125I radioactive seeds permanent interstitial brachytherapy for radiation oncologists performing brachytherapy. These expert consensus statements for CT-guided 125I radioactive seeds permanent interstitial brachytherapy represent clinical guidelines for clinicians performing this common procedure and selection criteria for undergoing patients.

This expert consensus statement on CT-guided 125I radioactive seeds permanent interstitial brachytherapy is intended to develop expert consensus statement for recommendations of patient selection criteria, prescription dose, and procedure of CT-guided 125I radioactive seeds permanent interstitial brachytherapy, which promote the accuracy and safety. The consensus statement is based on the clinical practice, published literature, and prior published guidelines. We formed a committee to develop expert consensus statement. The leader of the group organized experts to write the first draft based on clinical experience and literature review and then sent the draft to the commissioner for consultation; finally, these expert consensus statements have been reviewed and reached a consensus. This expert consensus statement on CT-guided 125I radioactive seeds permanent interstitial brachytherapy is viewed as an aid for radiation oncologist to manage patients, but it is not judged as rigid practice requirements by which to establish a legal standard of care. This consensus is intended to present some technical recommendations and the treating physicians are eventually responsible for the medical decisions.

Despite the benefit of RSI for solid carcinomas, there are some issues that are extensive controversy and lack of evidence to make corresponding recommendations. There remained a compelling need for prospective, randomized, multicenter clinical trials to confirm the role of RSI in cancer treatment. The outcomes of RSI and research results are reported after clinical studies.

In conclusion, this expert consensus develops patient selection criteria. Guidelines for prescription dose of 125I seed for different kinds of carcinomas, activity of per se ed, and workflow of CT-guided permanent interstitial RSI are provided. These expert consensus statements for CT-guided 125I radioactive seeds permanent interstitial brachytherapy represent clinical guidelines for radiation oncologists performing this common procedure and selection criteria for undergoing patients with unresectable carcinomas and locally recurrent cancers.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
 > References Top

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