Preoperative preparation for patients with colorectal cancer includes the following three purposes: to reduce postoperative complications such as surgical site infection or anastomotic leakage, to improve postoperative quality of life such as avoiding placement of an artificial anus, and to improve postoperative outcomes. The current status of these three purposes is described. Regarding treatments to reduce postoperative complications, mechanical preoperative preparation, which is not recommended by ERAS, was performed in many institutions in Japan. In contrast, chemical preoperative preparation, which is recommended by the American CDC guidelines, was performed in few institutions in Japan. The transanal ileus tube and SEMS for patients with obstructive colorectal cancer were very useful as “bridges to surgery” and also reduced the frequency of placement of an artificial anus. Preoperative chemoradiotherapy for patients with advanced rectal cancer significantly reduced local recurrence. However, the improvement of postoperative outcomes remains unclear.
This review describes the current status of treatment for obstructive colorectal cancer, the practice and indications of decompression therapy, and the usefulness of the transanal decompression tube (TDT) in decompression therapy. For obstructive colorectal cancer that requires urgent treatment as a so-called “oncologic emergency,” a colostomy, Hartmann operation, and decompression therapy using the TDT or self-expandable metallic colonic stent are performed.
Decompression therapy for “BTS,” which is premised on radical resection, reduces perioperative complications by improving the general condition, and it is safe and can evaluate surgical tolerance and other colorectal cancer of the oral side. As a result, radical elective surgery becomes possible. A stent has many advantages in short-term results, but there is no difference in the long-term results between the TDT and stent, and the TDT is expected to have the same therapeutic effects as a stent. In addition, the TDT is an optimal indication for lower rectal cancer near the anus. Decompression therapy by inserting the TDT is an effective method and should be performed along with stent placement.
After gaining health insurance coverage in 2012, intestinal decompression using a self-expandable metallic stent (SEMS) for malignant large bowel obstruction (MLBO) has spread rapidly in Japan. Regarding preoperative decompression using SEMS, called “bridge to surgery” (BTS), there are concerns about the long-term outcomes; the guideline from the European Society of Gastrointestinal Endoscopy (ESGE) 2014 did not recommend BTS as a standard therapy for left-sided MLBO. Recent meta-analyses and large-scale retrospective studies using propensity score matching regarding the long-term outcomes demonstrated equivalent survivals, but the possibility of higher recurrence rates, compared with emergency surgery. The updated ESGE guideline 2020 recommended that BTS be discussed within a shared decision-making process as a treatment option. However, a number of clinical questions in the BTS strategy, concerning long-term outcomes, interval from SEMS placement to surgery, type of SEMS, application in right-sided MLBO, and comparison with transanal decompression tube, are still under investigation. To secure the safety and efficacy of BTS, compliance with strict indications and experienced skills of endoscopic procedures, which are emphasized in the guideline, are indispensable. This review describes the current status of BTS for MLBO and the future perspectives of this less invasive and promising treatment strategy.
The current Japanese standard treatment for colorectal cancer is still upfront surgery followed by adjuvant chemotherapy, however, the treatment results are unsatisfactory. For further improvement, an alternative method is to shift part of adjuvant chemotherapy to the preoperative period. Neoadjuvant chemotherapy (NAC) could be introduced at any institution, unlike chemoradiation (CRT), and has gradually become widespread in daily practice. On the other hand, NAC without CRT for poor-risk rectal cancer could be generally accepted in Western countries. Although long-term results after NAC and data for comparison with chemoradiation or upfront surgery are lacking, a few clinical trials recently demonstrated it. Survival after NAC and CRT might be equivalent, however, local control after NAC seemed to be inferior to that after CRT. NAC could be a treatment option in selected patients with colorectal cancer. Moreover, treatment for locally advanced colorectal cancer should be personalized.
Preoperative short-course radiotherapy (SCRT) for lower rectal cancer has been reported to be useful for local control in Europe. SCRT was compared to long-course chemoradiotherapy (LCCRT) in several RCTs. In those analyses, SCRT is superior to LCCRT in terms of treatment compliance and cost effectiveness. However, there was no statistical difference in local control rate, overall survival and sphincter preservation rate. In the guidelines, preoperative short-course radiotherapy or conventional chemoradiotherapy is recommended for resectable, negative circumferential margin cases, and systemic chemotherapy with short-course or long-course radiotherapy for involved circumferential margin cases.
Organ preservation in cases with rectal cancer with nonoperative management has developed as a novel promising strategy in recent years. This strategy avoids total mesorectal excision in patients who achieve clinical complete response (cCR) after neoadjuvant chemoradiotherapy. Multiple studies reported comparable oncologic outcomes of nonoperative management and conventional total mesorectal excision. With the recent development of total neoadjuvant therapy with a higher cCR rate, more patients with rectal cancer would likely benefit from nonoperative management.
In contrast to Western countries, neoadjuvant chemoradiation is not a standard treatment for rectal cancer in Japan, which greatly hinders the development of nonoperative management. On the other hand, Japanese surgeons have advantages in developing this strategy, including meticulous endoscopic assessment using magnifying chromoendoscopy and the widespread use of minimally invasive surgery. In this review article, the rationale, indications and outcomes of nonoperative management for rectal cancer are discussed.
In Japan, colorectal neuroendocrine tumors (NET) most commonly arise in the rectum, particularly the lower portion. Many lesions are asymptomatic and detected when they are 10 mm or less in diameter. Endoscopic examination typically shows a yellowish, submucosal tumor, often with dilated blood vessels on its surface. Endoscopic ultrasonography is useful for evaluating the depth of invasion. In a rectal NET, the macroscopic type and size of the tumor are closely related to the depth of invasion and the risk of metastasis to lymph nodes. In particular, when the pedunculated macroscopic type, central depression, or tumor diameter is 10 mm or more, the risk of invasion to the proper muscle layer and metastasis increases, so caution is required. Regarding the prognosis, it has been reported that colon NET is worse than rectal NET, but it is necessary to examine many cases in the future.
In this article, the pathological diagnosis of neuroendocrine tumor (NET) and recent findings are summarized. In Japan, 90% or more of colorectal NET is found in the rectum, belonging to the hindgut system. Rectal NET has immunohistochemical characteristics different from those of midgut NET, such as a low positive rate of Chromogranin A. Regarding the classification of NET, the subclassification was changed in the 5th edition of the WHO classification of the digestive system published in 2019. The new subclassification applies both the histological findings, including cytological atypia and tumor differentiation, and the proliferation index. This makes it possible to clearly distinguish between NET, which has a high growth index, and neuroendocrine carcinoma (NEC), which has a high degree of malignancy and different genomic abnormalities and drug treatment responsiveness. This concept is closer to the Japanese way of thinking. In recent years, biomarkers other than the proliferative index have been reported and are expected to be incorporated. Appendiceal goblet cell carcinoid was renamed to appendiceal goblet cell adenocarcinoma in the 5th edition of the WHO Classification, making it clear that it was a different tumor from NET.
When a rectal SMT with yellowish color especially in the lower rectum is detected, a neuroendocrine tumor (NET) is the most likely. It is strongly recommended to confirm that the tumor surface is covered with normal mucosa by using the dye spray method, in addition to endoscopic ultrasonography. Endoscopic resection is recommended when no depressed surface or ulcer is observed on the tumor surface and the tumor is confined to T1 (SM). As for endoscopic resection methods, conventional polypectomy and EMR are not suitable due to the high rate of histological positive vertical margin. EMR by dual channel scope, EMR by cap method (EMRC), EMR with a ligation device method (ESMR-L) or endoscopic submucosal dissection (ESD) are preferable. According to a meta-analysis, the cap method, EMR-L, and ESD had a higher complete resection rate than conventional EMR. Post-resected specimens should be evaluated for risk factors for lymph node metastasis to determine whether additional treatment is required or not, with a comprehensive assessment of the patient's age, physical activity level, comorbidities, and so on. There have been reports that good prognoses of patients were obtained after endoscopic resection of the indicated size.
It is sometimes difficult to choose local excision or bowel resection with lymph node dissection as the surgical treatment for colorectal NET (neuroendocrine tumor). The latter surgery is necessary when the risk of lymph node metastasis is high. The size of the metastatic lymph node for rectal NET on the preoperative CT image is smaller than that of rectal cancer. It is very difficult to identify the true metastatic lymph node accurately. We analyzed 387 cases of colorectal NET from a nationwide retrospective cohort to determine the predictive risk factors of lymph node metastasis.
Five predictive risk factors were found: tumor size (≥10 mm), superficial depressed type, NETG2, depth of invasion (proper muscle or deeper) and lympho-vascular invasion. The rates of lymph node metastasis by the number of these risk factors were as follows: no factor: 0.7%, 1 factor: 19.1%, 2 factors: 20.7%, 3 factors: 61.9%, 4 factors: 75.0% and 5 factors: 75.0%. Cases with more than two factors showed the highest rate of lymph node metastasis. It is considered that the type of surgery should be decided based on these five predictive risk factors.
There are increasing chances to treat colorectal NET, which is mainly composed of rectal NET in Japan. As a result, the importance of post-treatment management for colorectal NET, including additional treatment and surveillance, has been increasing. However, there remain many unsolved issues regarding post-treatment management for colorectal NET, and thus clinicians often have difficulties with such management in daily practice. With respect to additional treatment, it is unclear whether additional surgery is really required for colorectal NET sized <1cm without invasion to the muscularis propria even if one of the following conditions is met: positive lymphovascular invasion, NET G2 or a positive cut margin. This issue is particularly important for rectal NET because of the invasiveness of surgical treatment for rectal lesions. Regarding surveillance, no programs have been established based on high-quality evidence. In this report, we review the post-treatment management (additional treatment and surveillance) for colorectal NET, including the current problems.