13.2 Current Additional Surgical Resection Criteria for Endoscopic Resected Colorectal pT1 (SM) Cancer

The JSCCR Guidelines for the Treatment of Colorectal Cancer 2016 in accordance with the GRADE system [1] specify the following criteria for indication of additional treatment for endoscopic resected T1 colorectal cancer as follows (Fig. 13.2):

1. 1.
   
   
   

   If the vertical tumor cut margin is positive, additional surgical resection is preferred (recommendation level/evidence level 1C).

   
   
    
   
   
2. 2.
   
   
   

   If one or more of the below findings is noted in the histological examination of the resected specimen, additional surgery with lymph node dissection should be considered (evidence level B).
   

   
   

   
   
   1. (a)
      
      
      

      SM invasion depth is ≥1000 μm.

      
      
       
      
      
   2. (b)
      
      
      

      Vascular invasion.

      
      
       
      
      
   3. (c)
      
      
      

      The presence of poorly differentiated adenocarcinoma, signet-ring cell carcinoma, mucinous carcinoma.

      
      
       
      
      
   4. (d)
      
      
      

      Budding grade at the deepest portion of the invasive front—Grade 2/3.

      
      
       
   
   
    

Since the guidelines committee did not reach a consensus regarding (2) revealed above, the recommendation level has not been described thus far.

The guideline “additional surgery with lymph node dissection should be considered” does not mean that the cancer should be surgically resected; rather, it conveys that surgical resection should be thoroughly considered as described in Fig. 13.3. Namely, at first we have to compare comprehensively the curability of colorectal cancer based on concrete percentage metastatic risks predicted by a combination analysis of various risk factors for lymph node metastasis. Next, we have to understand the patient background (patient’s will, age, level of physical activity, complications, postoperative quality of life, etc.). Finally, we have to determine carefully whether additional surgery is necessary or not with enough informed consent [1].

13.3 Recent Information on Management of Colorectal T1 Cancer

Based on the recent accumulation of cases, it has been clarified that additional surgery with lymph node dissection is not always necessary, even in endoscopic resected pT1b (SM invasion depth is ≥1000 μm) cancer. In addition, there has also been evaluated as clinical research regarding the feasibility of endoscopic resection as total excisional biopsy for cases of SM invasive cancer that have previously been indicated for surgery, depending on various conditions [2].

We reported a 1.2% of lymph node metastatic risk of T1 colorectal cancer, irrespective of the degree of SM invasion, if the following conditions were never detected: (1) the presence of vascular invasion; (2) poorly differentiated adenocarcinoma, signet-ring cell carcinoma, or mucinous carcinoma; and (3) at the deepest portion of the invasive front—budding Grade 2/3 [3]. Yoshii et al. [4] investigated the prognosis of T1b cancer after endoscopic resection and reported that in the absence of unfavorable histology, vascular invasion, and high degree of budding grade, the recurrent rate with endoscopic resection alone was 3.4% and that with endoscopic resection plus additional surgery was 2.3%; the rates were low in both groups with no significant difference. In addition, recently, the JJSCCR undertook the “Project research on the stratification of the metastatic risk of SM T1b cancer (Committee Chair, Prof Yoichi Ajioka)” and found that even cases with T1b cancer, when no other metastatic risk factors besides SM deep invasion (i.e., unfavorable histology components, vascular invasion, and high degree of budding grade) were observed, the rate of lymph node metastasis was only 1.4% (data under submission preparation).

Yoda et al. [5] investigated the prognosis after endoscopic treatment of T1 cancer in 302 cases that were considered for additional surgery and found that the recurrence rate was 3.6% for 196 cases who required additional surgery and 6.6% for 106 cases who underwent endoscopic resection alone with further surveillance; the recurrence rate was significantly higher in the latter. However, we have to pay attention to the fact that even with additional surgery, 3.6% of patients experience recurrence. On the other hand, in a multicenter study (14 centers), Kobayashi et al. [6] reported that surgery without preceding endoscopic treatment yielded the following results: overall postoperative recurrence rate was 2.3% in 798 patients with colorectal T1 cancer (excluding transanal resection) that was surgically resected with lymph node dissection (recurrence rates: 1.5% for colon cancer and 4.2% for rectal cancer, P = 0.02), and lymph node metastasis and histologic grade were independent risk factors (poorly differentiated or mucinous, P < 0.0001). Further, according to a survey by the Japanese Society of Gastroenterological Surgery [7], the nationwide mean incidence of operational death during colorectal surgery is 0.24–0.7%, which indicates a constant, albeit low, risk of operational death.

As stated above, it is important to acknowledge the following information when considering additional surgery for pT1b cancer after endoscopic resection: (1) the incidence of lymph node metastasis is 1.2–1.4% if there are no other metastatic risk factors, even with SM highly invasive cancer; (2) the postoperative recurrence rate is 2.3%, even in T1 cancer treated by surgery with lymph node dissection, and this recurrence rate is 1.5% for colon cancer and 4.2% for rectal cancer; and (3) the incidence of operational death from surgery is not 0%.

13.4 Future Direction for Management (Endoscopic Treatment) for Colorectal T1 Cancer

With the current aging society, many factors such as the patient’s age, underlying disease, level of physical activity, patients’ will, and possibility of a colostomy (Miles’ operation) should be considered in order to determine whether a patient should undergo surgery. In particular, the postoperative quality of life after Miles’ surgical procedure for lower rectal cancer is problematic in terms of sexual and excretory function. Then finally, the patient himself/herself must decide whether he/she will undergo the surgery by enough understanding of disease and discussion with doctor (Fig. 13.3).

In the near future, it is highly likely that colorectal cancer treatment will move toward a strategy of evaluating the risk of lymph node metastasis using completely resected colorectal T1b cancer. After en bloc endoscopic resection as excisional total biopsy for colorectal T1 cancer, necessity of the additional surgery can be considered (Fig. 13.4) [2]. In such cases, although the relative classification of SM invasion (SM1, SM2, SM3) [8] cannot be used for endoscopic resected specimens, it will be a simple and effective indicator to decide whether cT1 cancer can be endoscopically resected. Endoscopic resection as total excisional biopsy should not be indicated for SM3 lesion in contact with the muscle layer, because SM3 lesion is highly likely to have positive deep tumor margins. However, endoscopic resection may be indicated for SM1–SM2 lesions, which have space between the tumor and the muscle layer. Ultrasound sonography can evaluate the transmural structure and can be used for such endoscopic evaluation [2, 9, 10].

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