Clinical study of harvesting lymph nodes with carbon nanoparticles in advanced gastric cancer: a prospective randomized trial
- Ziyu Li†1,
- Sheng Ao†1, 3,
- Zhaode Bu1,
- Aiwen Wu1,
- Xiaojiang Wu1,
- Fei Shan1,
- Xin Ji1,
- Yan Zhang2,
- Zhaodong Xing1 and
- Jiafu Ji1, 4Email author
© Li et al. 2016
Received: 16 June 2015
Accepted: 1 March 2016
Published: 24 March 2016
The objective of this study is to evaluate the efficiency and safety of carbon nanoparticles (CNPs) for harvesting lymph nodes (LNs) in cases of advanced gastric cancer (AGC).
Patients with previously untreated resectable AGC were eligible for inclusion in this study. All patients were randomly allocated to two subgroups. In the experimental group, 1.0 mL of CNP was injected into the subserosa of the stomach around the tumor before gastrectomy with D2 dissection. The same procedure was performed directly without any coloring material in the control arm. Following surgery, LNs were harvested, colored LNs were counted, and the diameters were measured by the investigator and pathologist.
Thirty patients were enrolled in the study. We observed no serious adverse effects related to CNP injection. The rate of stained LNs was 46.6 %. The mean number of harvested LNs was larger in the experimental than in the control group (38.33 vs 28.27, p = 0.041). A smaller diameter of LNs was recorded in the experimental arm (3.32 vs 4.30 mm, p = 0.023). In addition, we developed a model for predicting the total number of LNs based on the data from CNP-stained LNs and metastatic LNs (MLNs).
CNP is a safe material. Surgeons could harvest more LNs in patients with AGC. The harvest of an increased number of smaller diameters of LNs may be beneficial. Further study is warranted to demonstrate the model’s practicality.
Although gastric cancer decreased from being the most common cancer in 1975 to being the fifth most common neoplasm in 2012, it remains the third leading cause of cancer death worldwide, contributing to 723,000 deaths annually [1, 2]. Screening and broad-based awareness of the disease has improved the identification rates of early-stage cancers and superior survival. However, compared with some developed countries, such as Japan, a majority of patients are diagnosed with advanced gastric cancer (AGC) in China, which presents a treatment challenge.
Gastrectomy with D2 lymph node (LN) dissection is the standard treatment for AGC in Asia because of the survival benefit and low complication rate [3, 4]. A similar study result was published recently with data from western countries . There was no controversy on the necessity of dissecting lymph nodes. In the light of guidelines, histopathological examination of at least 15 regional lymph nodes is necessary to accurately assign the N category for gastric carcinoma. Intriguingly, undoubtedly reflecting the contribution of stage migration and dissecting more metastatic LNs, representing the quality of the operation, overall survival (OS) improved incrementally with higher LN counts [6–8]. Based on these results, we attempted to develop a method to obtain more LNs. In other studies, lymphatic tracers, including dye materials, have been used to meet this need . Carbon nanoparticles (CNPs) are a practicable material for harvesting lymph nodes in our department.
CNPs with a mean size of 150 nm can be taken up selectively by the lymphatics after injection into the tissue. The draining regional lymph nodes are thereby colored black, which may provide guidance to the surgeon during lymph node dissection and help harvest lymph nodes after surgery, especially smaller LNs. However, there is insufficient evidence to justify its efficacy for those purposes. Therefore, we carried out a prospective randomized controlled trial on lymph node vital staining for LN dissection and harvesting in AGC.
CNP staining, open gastrectomy with D2 dissection, and lymph node harvesting
After surgery, the investigator (Sheng Ao) harvested the lymph nodes with the pathologists (10 min for each patient’s specimens) and simultaneously counted the colored LNs. The tissues were fixed in formalin solution and embedded in paraffin for histological examination with H&E staining. Then, the diameters of each LN were measured.
This study was designed as a single-center prospective clinical trial. The procedure was approved by the Ethics Committee of Beijing Cancer Hospital. The study protocol was released on ClinicalTrials.gov (ID: NCT02123407).
The primary outcome measure was to calculate the number of harvested LNs. The second outcome measure was the diameter of the harvested LNs, which was aimed to obtain the maximum dimension to reflect the degree of difficulty of picking up LNs. In addition, operation time, bleeding, and complications were compared between the two groups to confirm the safety of CNP.
Respectively, the average number of lymph nodes we harvested in advanced gastric cancer cases without CNP was 28.76 ± 1.14. The sample size was set at 30 (15 each group) based on the assumption that the expected number of LNs should increase by at least one, with a two-sided alpha of 5 % and at least 90 % power. The planned duration of accrual was 7 months. All statistical analyses were conducted with SPSS 17.0 software.
Clinical characteristics of patients
25.45 ± 3.60
23.80 ± 2.44
Operation time (min)
214.7 ± 42.9
212.9 ± 55.7
110.0 ± 63.2
98.7 ± 66.2
Mean number of harvested LNs
Means of lymph nodes
Mean diameter of harvested LNs
Means of diameter (mm)
Model for predicting total number of LNs
Lymphatic tracers, such as methylene blue, indocyanine green, and an intraoperative radiation technique with a gamma probe, had been widely used as guidance for lymph node searching and dissection for some years [11, 12]. It was initially confirmed that lymphatic tracers were useful to improve OS by harvesting more LNs. In fact, both surgeons and pathologists have trouble harvesting LN because of their busy workload, especially in China, which has the highest number of people in the world. Furthermore, no ideal materials were found due to the limitation of their staining efficiency, the relatively complicated lymphatic flow of the gastric system, radiation injury, and expense. Carbon particles, which are convenient, inexpensive, and widely available in general hospitals, have been used by others for LN staining and were shown to be safe [13, 14]. Similarly, in our study, no CNP-related side effects occurred, there was no extra bleeding, the length of surgery was not extended, and no extra complications were observed.
This prospective randomized controlled trial was mainly designed to test the efficiency of CNP. In the design research process, injection method was considered. Because lymphatic vessels are connected to each other by a communicating branch in the gastric wall which expands vertically, many researchers held the view that injection methods were equally efficient in lymph node staining in AGC [15, 16]. We obtained similar results in a preliminary experiment; thus, we selected to perform subserosal dye injection, which is an easier and more effective method during open surgery. Our staining rate was 46.6 %, somewhat lower than the rate reported in Japanese studies about early gastric cancer . There might be two reasons for this difference. First, more lymphatic vessels were blocked by the tumor in AGC. On the other hand, more LNs from the N2 station were dissected in AGC for the development of gastric surgery, which were more difficult to stain because of distance and lymphatic vessel complex structure.
Obviously, more LNs were harvested in patients with CNP staining (38.33 vs 28.27). The difference agreed with Catarci’s finding using CH40 (a type of dye material) . Nevertheless, we obtained a larger number of LNs and better standard gastrectomy with D2 dissection. However, subgroup analysis showed no more MLNs were harvested in the experimental group, which might be due to sample size. On the other hand, the higher ratio of the LN metastasis-positive patients than that of the control group indicated that CNP could help improve the discovery rate of metastatic LN, but more study are needed to prove the result.
Finally, we set up a forecasting model to evaluate the quality of the operation if CNP was used. Since the importance of statistics was noticed, more and more scientists, such as Gretschel , have combined it with medicine to solve clinical problems. To some extent, our model may help the surgeons review their work of removing LNs to improve their surgical skills. For instance, surgeons could compare their resected LNs to the predicting number calculated with this model to evaluate the quality of operation. However, this work should be tested in more cases.
Our results indicated that CNP was a safe material and that surgeons could harvest more LNs with it in cases of AGC, which might benefit from the harvest of an increased number of smaller LNs. The model we built in this study could play a role in evaluating the surgeon’s capacity and their training. However, further study is needed to prove its practicality.
This research was supported by Beijing Municipal Science and Technology Commission Foundation (D141100000414002) and the National High Technology Research and Development Program of China (863 Program) (2012AA02A203-B01).
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