Gastric cancer is the fifth most common cancer and third leading cause of mortality in the world, with highest incidence in East Asia (1,2). In Korea, the proportion of early gastric cancer (EGC) is increasing, accounting for approximately 60% of patients with gastric cancer. This is probably due to early detection of gastric cancer by national cancer screening program and individual check-up (3). The standard treatment of EGC is gastrectomy with lymph node dissection, and endoscopic submucosal dissection (ESD) is also indicated for patients with a negligible risk of lymph node metastasis (4,5). The overall incidence of recurrence after curative resection of EGC has been reported to be rare. After curative ESD of EGC, most recurrence involves the ESD site or remnant stomach, and extragastric recurrence is extremely rare (6,7). For patients who underwent surgical resection of EGC, overall recurrence has been reported in 1.0 to 13.8% of patients, whereas the incidence of extragastric recurrence has not been well described.
2. Follow-up strategy after curative resection of EGC
Patients with EGC after curative resection have favorable outcome with more than 97% of a 5-year overall survival rate (4,8,9). However, there has been no established strategy for postsurgical surveillance in these patients. To date, there has been no prospective study on this issue, and current retrospective trials failed to show a survival improvement with intensive surveillance for gastric cancer after surgical resection (10,11). Nonetheless, postsurgical surveillance cannot be abandoned in oncologic patients, because there are certain roles such as early detection of recurrence, identification of secondary malignancies, and patient reassurance (12).
Major methods of postsurgical follow-up in gastric cancer includes carcinoembryonic antigen (CEA), carbohydrate antigen (CA) 19-9, endoscopy, and abdominopelvic CT. Tumor markers (CEA, CA 19-9) are less useful in gastric cancer patients without increase in the preoperative work-up (13). Endoscopy is effective to detect intraluminal recurrence, metachronous lesion, and gastric stump disease. Abdominopelvic CT is an efficient tool to detect tumor recurrence, because most recurrence occurs in the abdomen and pelvis in patients with gastric cancer. Abdominopelvic CT is particularly useful to detect extragastric recurrence, whereas small intragastric recurrence is usually not detectable on CT (3,6) (Fig. 1). As majority of recurrence occurs within the first 3 years after surgical resection, particularly for patients with advanced gastric cancer (AGC), CT is performed more frequently within 2-3 years from surgery in some institutions (5,14,15).
Image
Figure 1. Local tumor recurrence in a 50-year-old man who underwent subtotal gastrectomy for early gastric cancer (EGC).
An endoscopic image (left) shows irregular nodular infiltration in the remnant stomach, suggesting recurrent malignancy. However, local recurrence was not detected on a contrast-enhanced axial CT image (right).
3. Role of CT surveillance in patients with EGC
Many institutions do not have different strategies for postsurgical surveillance of AGC and EGC. According to the Japanese guidelines, abdominopelvic CT is recommended biannually within one year, and then annually up to five years after surgery for stage I gastric cancer patients (5). However, we rarely identify recurrence on CT after surgical resection of EGC, probably due to low incidence of recurrence and poor diagnostic performance of CT for gastric recurrence. Due to the risk of radiation exposure, unnecessary CT scans should be avoided as possible. Since the major role of CT is to detect extragastric recurrence, postsurgical CT surveillance should be based on the incidence and risk of extragastric recurrence in patients with EGC.
In our study to develop a risk-scoring system to predict extragastric recurrence after curative surgical resection of EGC, only 1.4% (44/3162) of patients had extragastric recurrence (3). The most involved organ was liver, followed by lymph node, peritoneum, and bone. There are six preoperative risk factors associated with extragastric recurrence: male sex, elevated macroscopic type, submucosal depth of invasion, positive lymphovascular invasion, LN metastasis, and beyond indications for ESD. Among these, last two variables were independent predictors for extragastric recurrence on multivariable analyses. Using a risk-scoring system with these variables, extragastric recurrence could be accurately predicted with C-index of 0.870. Of note, there was no recurrence in low-risk group within 2 years after surgery (3). This prediction model can be valuable to stratify the postsurgical CT surveillance protocol according to the risk of extragastric recurrence in patients with EGC after curative resection. Based on this prediction model, we could suggest that CT surveillance might be unnecessary in the low-risk group, and frequent CT follow-up within 2 years after surgery should be avoided in the low-risk group.
References
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