As an emerging tumor marker, the rarity and heterogeneity of circulating tumor cells (CTCs) increase the difficulty of detection. In recent years, CTCs enrichment technology based on biophysical, biochemical and microfluidic properties has been continuously developed, which has promoted the research and application of CTCs in malignant tumors diagnosis, clinical treatment and prognosis evaluation. Although there are still some deficiencies in the detection of CTCs, with the interdisciplinary integration, CTCs will play increasingly important roles in the diagnosis and treatment of malignant tumors.

To adapt to the need of current public heath reform and education reform ,the aim of this study is to explore and improve practical teaching mode in preventative medicine for students in specialty of clinical medicine and set up normalized practical teaching base to enhance their concept of preventative medicine and enlarge their knowledge and increase their practical ability and social adoption.

The incidence of gastric cancer ranks the fourth in all kinds of cancers in the world,ranking the second among patients with cancer-related deaths.The 5-year survival rate of gastric cancer patients is less than 30％.About 50％ of gastric cancer patients have recurred or metastasized after curative resection.Metastasis and recurrence are the major causes of death in cancer patients.CTCs play an important role in tumor metastasis.At present,there are more than 10 kinds of detection methods for CTCs in gastric cancer.The most widely used methods are RT-PCR,FCM,CelLTracks(R) AutoPrep(R) system and ISET.Recent studies have shown that CTCs in peripheral blood of patients with gastric cancer can be used to determine the clinical stage of patients,assess the prognosis and guide the individualized treatment of cancer.

There are many ways to identify circulating tumor cells in the current.Fluorescence has a wide range of applications in the identification of circulating tumor cells.The labeled cells can be observed and counted more intuitively by labeling the tumor cells with fluorescent group containing antibodies,probes and aptamers,and cytokine,CD45 and fluorescence in situ hybridization are widely used in the identification of various circulating tumor cell related tests.In recent years,people have explored the feasibility of using fluorescent probes to directly identify circulating tumor cells.With the development of biopsy probes and optical sectioning imaging technology of confocal microscopy,it is possible to directly identify circulating tumor cells with fluorescent probes in the future.

Objective:To investigate the specimen quality of intersphincteric resection with transabdominal transanal mixed approach for rectal cancer in the Chinese Transanal Total Mesorectal Excision Registry Collaborative (CTRC) database.Methods:The retrospective case-control study was conducted. Based on the concept of real-world research, the clinicopathological data of 281 pati-ents with rectal cancer in the CTRC database who underwent intersphincteric resection with trans-abdominal transanal mixed approach in 19 medical centers, including the Beijing Friendship Hospital of Capital Medical University et al, from November 15,2017 to December 31,2023 were collected. There were 196 males and 85 females, aged 61(range, 27-87)years. Observation indicators: (1) preoperative examinations; (2) neoadjuvant therapy; (3) postoperative examinations; (4) analysis of influencing factors for positive circumferential margin in surgical specimen of intersphincteric resec-tion for rectal cancer. Measurement data with normal distribution were represented as Mean±SD. Measurement data with skewed distribution were represented as M(range). Count data were described as absolute numbers or percentages. The chi-square test was used for univariate analysis. Logistic regression model was used for multivariate analysis. Results:(1) Preoperative examinations. Of the 281 patients, 234 cases underwent preoperative pelvic magnetic resonance imaging (MRI) examina-tion. There were 2 cases in clinical stage T0, 3 cases in clinical stage T1, 58 cases in clinical stage T2, 137 cases in clinical stage T3, 24 cases in clinical stage T4, 3 cases in clinical stage Tx, 7 cases missing clinical T staging data. There were 87 cases in clinical stage N0, 68 cases in clinical stage N1, 60 cases in clinical stage N2, 9 cases in clinical stage Nx, 10 cases missing clinical N staging data. There were 30 cases with mesorectal fascia invasion, 53 cases with extramural venous invasion. The distance from lower margin of tumor to anal margin was 41.9(range, 1.0-80.0)mm. (2) Neoadjuvant therapy. Of the 281 patients, 125 cases underwent neoadjuvant therapy, including 39 cases receiving chemo-therapy alone, 6 cases receiving short-course simultaneous chemoradiotherapy, 5 cases receiving short-course simultaneous chemoradiotherapy and delayed surgery, 48 cases receiving long-course simultaneous chemoradiotherapy, 2 cases receiving other treatments, and 25 cases missing neoadju-vant therapy data. (3) Postoperative examinations. Of the 281 patients, 249 cases achieved R 0 resection, 9 cases achieved R 1 resection, and there were 23 cases missing surgical margin data. The maximum tumor diameter, the number of lymph nodes harvested and positive rate of vessel carcinoma embolus were 30.0(range, 0.5-200.0)mm, 13(range, 0-70) and 27.55%(73/265) in 281 patients. There were 252 patients with circumferential margin records, showing positive in 15 cases, with a positive rate as 5.95%(15/252). The minimum distance from deep part of tumor to circumferential margin was 7.0(range, 0-150.0)mm in 252 patients. There were 85 cases with distal margin records, showing positive in 1 case, and the distance from lower margin of tumor to distal margin was 10.0(range, 0-202.0)mm. There were 273 patients with specimen integrity records, which showed intact specimen in 208 cases, fair specimen in 58 cases, poor specimen in 4 cases, unevaluated specimen in 3 cases. There were 7 cases with rectal perforation. Of the 281 patients, cases in pathological stage T0, Tis, T1, T2, T3, T4 were 14, 5, 22, 107, 113, 12, respectively, and there were 8 cases missing pathological T staging data. Of the 281 patients, cases in pathological stage N0, N1a, N1b, N1c, N2a, N2b were 176, 27, 27, 11,20, 12, respectively, and there were 8 cases missing pathological N staging data. Of the 281 patients, there were 4 cases with distant metastasis, 262 cases without distant metastasis, 5 cases not evaluated, and 10 cases missing tumor metastasis data. Of the 125 patients undergoing neoadjuvant therapy, there were 85 cases with tumor regression grade records, including 16 cases as grade 1, 27 cases as grade 2, 19 cases as grade 3, 15 cases as grade 4, 8 cases as grade 5. (4) Analysis of influencing factors for positive circumferential margin in surgical specimen of intersphincteric resection for rectal cancer. Results of univariate analysis showed that preoperative T staging on preoperative pelvic MRI, mesorectal fascia invasion, extramural venous invasion, pathological T staging, and pathological N staging were related factors for positive circumferential margin in surgical specimen of intersphincteric resection for rectal cancer ( P<0.05). Conclusions:Intersph-incteric resection with transabdominal transanal mixed approach has good specimen quality and low positive rate of surgical margin. T staging on preoperative pelvic MRI may be related to positive circumferential margin after intersphincteric resection for rectal cancer.