Review Article

Update on Diagnosis and Treatment of Colorectal Cancer

Chan Wook Kim 1 , * https://orcid.org/0000-0002-2382-0939
Author Information & Copyright
1Department of Colon and Rectal Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea
*Corresponding author: Chan Wook Kim, Department of Colon and Rectal Surgery, Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul 05505, Korea, Tel: 82-2-3010-3928, Fax: 82-2-3010-6710, E-mail: crscwkim@amc.seoul.kr

© Copyright 2022 Ewha Womans University College of Medicine and Ewha Medical Research Institute. This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Received: Sep 30, 2022; Accepted: Oct 04, 2022

Published Online: Oct 31, 2022

ABSTRACT

The rate of colorectal cancer (CRC) has altered. Early-onset CRC patients are increasing, and it is one of the main causes of cancer-related death. Based on epidemiologic change, the CRC screening program needs to be changed. To increase compliance, non-invasive screening techniques are developed. Although CRC survival has increased, the oncologic prognosis of metastatic CRC is remains poor. Even in metastatic CRC, which is the most difficult to treat, attempts are being made to increase the survival rate by active surgical therapy with the creation of chemotherapeutic regimens and targeted treatment based on genomic information. Due to the introduction of aggressive chemotherapy regimens, targeted therapy based on genomic features, and improvements in surgical technique, the role of surgical treatment in metastatic CRC has expanded. Metastatic CRC surgery was indicated for liver, lung, and even peritoneal seeding. Local ablation therapy was also effectively used for liver and lung metastasis. Cytoreductive surgery and intraperitoneal chemotherapy were tried for peritoneal seeding and demonstrated good results in a subgroup of patients, although the right indication was carefully assessed. At the same time, one of the key goals of treatment for CRC was to maintain functional outcomes. Neoadjuvant treatment, in particular, helped rectal cancer patients preserve functional results while maintaining oncologic safety. Rectal cancer organ preservation techniques are now being researched heavily in a variety of neoadjuvant treatment settings, including immunotherapy and whole neoadjuvant therapy. Precision medicine based on patient and disease characteristics is currently being used for the diagnosis and treatment of CRC.

Keywords: Colorectal neoplasms; Screening; Metastatic; Neoadjuvant therapy; Precision medicine

Introduction

In 2019, cancer is the leading cause of death in Korea, and colorectal cancer (CRC) is one of the most prevalent malignancies worldwide [1,2]. CRC is the second leading cause of cancer-related death and the third most prevalent malignancy globally [2]. Thyroid, lung, stomach, colorectal, and breast cancer were the five most frequently diagnosed malignancies in Korea in 2019 according to statistics from the National Cancer Registration Project of the Central Cancer Registry of Korea. After stomach and lung cancer in males and breast and thyroid cancer in women, CRC is the third most frequent malignancy in both sexes [1]. Since 1999, the incidence of CRC has been consistently rising; however, it has been slowly declining since about 2011. Both rectal and colon cancers exhibit the same incidence trend (Fig. 1). Although adenocarcinoma makes up the majority of CRC cases, neuroendocrine tumors are the most common non-adenocarcinoma [3]. A feature worth observing is the lowering of the age of onset, and it has been observed that in industrialized nations, the prevalence of early-onset CRC in those under 50 is rising, increasing social awareness It is very obvious that CRC incidence is rising among the elderly. The growing older population in good health appears to be the cause. A national investigation on the treatment strategy for advanced CRC seems necessary given the current trend toward an aging society [1,2,4].

emj-45-4-8-g1
Fig. 1. Age-standardized incidence rates of colorectal cancer in Korea, 1999–2019. Adapted from Kang et al. [1] with CC-BY-NC.
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Overall survival (OS) rates for CRC patients in Korea are extremely high, and the relative OS rate for CRC patients is reported to be 74.3% of patients diagnosed between 2015 and 2019 [1]. In Korea, the OS rate of CRC varies by gender, with men having a greater rate than women. The increased survival rate in men is thought to be due to the average age of CRC diagnosis being older in women than in men and the presence of more right-sided CRC in women, despite the fact that the precise mechanism is unknown [1,2,5]. Although the survival rate for CRC in stages I-III is increasing, there is still an issue because the increase in the OS rate for CRC with metastatic disease is not significant.

Advances in Colorectal Cancer Screening and Diagnosis

The cost, compliance, sensitivity, and specificity of the test, as well as other factors, are taken into account while choosing the screening test to be used. Fecal occult blood test, an immunochemical test method, is now employed in Korea as the first line screening test for national health screening. Although there is still debate regarding the accuracy of the diagnosis of polyps or CRC, the non-invasive test has the significant advantage of high compliance. There will not be any debate on the importance of colonoscopy in the timely diagnosis and treatment of precancerous lesions and early CRC. Due to the invasiveness and low compliance of the colonoscopy as a primary screening test, it is crucial to weigh this option [6,7]. Fecal occult blood testing every one to two years for asymptomatic persons aged 45 to 80 is the current CRC screening prescription in Korea, and colonoscopies are only occasionally conducted according on individual risk. The question of whether colonoscopy can be used as a primary screening test is being investigated in Korea as a pilot project, but it is still necessary to make decisions about potential complications and costs, whether the examination can be restricted based on bowel preparation, and how to assess the operator's skill. In particular, the screening test may only be used and assessed for effectiveness after extensive research and development on how to improve patient compliance.

More accurate non-invasive screening methods have been developed in an effort to replace the fecal occult blood test, which is the current screening method [810] (Table 1). The test that seeks to identify tumor epithelial DNA in feces in order to diagnose CRC is now coming the closest to clinical application. An assay for mutant KRAS, methylation BMP3, methylated NDRG4, and a fecal immunochemical test for hemoglobin were all included in the FDA-approved multi-target fecal DNA test [8]. In a research involving 9,989 average-risk people having colonoscopy, the multi-target fecal DNA test demonstrated better sensitivity for the diagnosis of CRC (92% vs. 74%) and advanced adenoma (42% vs. 24%) when compared with fecal immunochemical test test. In 2018, the Ministry of Food and Drug Safety in Korea approved the EarlyTect fecal DNA test (Genomic Tree, Daejun, Korea), which only examines the methylation of one gene, the syndecan-2 gene [10]. The findings are significant since we are carrying out a prospective multicenter study with a focus on the asymptomatic general population over 60 or in the high-risk category. Due to its excellent disease prediction, non-invasiveness, and high compliance, this fecal DNA detection test is projected to be used as a screening tool. The poor identification rate of pre-cancerous lesions is a challenge; thus it is important to watch with greater skepticism what kind of outcomes will be seen in the long-term impact of CRC prevention in the future.

Table 1. Clinically available non-invasive screening method with stool DNA detection for colorectal cancer diagnosis
Product name Target Sensitivity, cancer Specificity, cancer Sensitivity, advanced adenoma detection
Cologuard [8] NDRG4, BMP3 DNA methylation, KRAS mutation, hemoglobin 92.3% 89.8% 42.4%
EarlyTect [10] SDT2 methylation, hemoglobin 90.2% 90.2% 66.7%

NDRG4, N-myc downstream-regulated gene 4; BMP3, bone morphogenetic protein 3; KRAS, Kirsten rat sarcoma virus; SDT2, synthecan 2.

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Changes to CRC screening are required in light of the rising incidence of CRC in people under the age of 50 [1,2,11] and the growing elderly population. Although the US Preventive Services Task Force and the Multi-Specialty Task Force currently recommend starting screening at age 50, the American Cancer Society published guidelines in 2018 with a qualified recommendation to lower the starting age for CRC screening from 50 to 45 years of age in the average-risk adult population [12]. Few empirical studies have been conducted on the effectiveness of screening in younger, average-risk persons [13,14], and it is unknown which screening method is best for this age group.

According to the US Preventive Services Task Force's most recent CRC screening recommendation for individuals aged 76 to 85, the choice to test for CRC should be made individually, taking into account the patient's general health and screening history [15]. According to the recommendation, screening is best recommended for people who have never been screened, are healthy enough to get treatment if CRC is found, and do not have significantly shortened life expectancies. Due to conflicting sources of death, screening is not advised for persons 86 years of age and older. Although further research is needed, healthcare professionals should participate in shared decision-making when evaluating people over 75 years old and take into account factors like life expectancy, patient risk, values, and preferences. It is crucial to advise when to halt screening in future research.

Development Surgical Treatment of Metastatic Colorectal Cancer

Despite a significant improvement in treatment outcomes for CRC, metastatic CRC therapy outcomes remain remarkably poor [1,2]. Therefore, we have worked hard to actively treat patients with metastatic disease in an effort to increase the OS of CRC patients.

Chemotherapy is the major treatment for CRC that has spread to other organs, and surgery is only occasionally employed. However, with advancements in systemic therapy, increased use of genetic information, and the development of surgical techniques, more individuals with metastatic CRC can benefit from curative-intent surgical surgery [1618].

Liver metastasis, common metastasis of CRC, is known as metastatic CRC that can improve the prognosis with surgery. Liver resection with or without local ablation therapy, such as radiofrequency ablation and stereotatic radiation (SBRT), can be used for curative treatment in CRC patients with liver metastases [1921]. Numerous prognostic factors and key drivers of resectability have included the size and location of liver metastases, as well as their distribution throughout the liver and the existence of extrahepatic metastatic lesions [20,22,23]. However, today, even in situations with multiple liver metastases, surgery is used when the likelihood of resection is verified through earlier chemotherapy, and in some instances, secondary resection is carried out in specific patients [2325]. In metastatic CRC patients with bi-lobar liver metastases and limited functional liver remnants, portal vein embolization can be used with CRC surgery to assure tumor regression and hepatic hypertrophy (FLR). The two-stage hepatectomy would also enable the total removal of bi-lobar liver metastases and FLR regulation. To get around the drawback of liver resection in CRC patients with a small FLR and numerous liver metastases, associating liver partition and portal vein ligation for phased hepatectomy (ALPPS) was created. According to reports, there was no discernible difference between ALPPS and two-stage hepatectomy in terms of postoperative morbidities and fatalities, although ALPPS had improved survival outcomes in randomized controlled trials [25,26].

Different strategies would be taken into consideration for individuals with synchronous liver metastases depending on their general health, the likelihood of curative resection, and extra-hepatic metastasis. There have been recommendations for simultaneous resection, liver-first strategy, and bowel first approach. Although a simultaneous liver and colon resection has advantages over a liver-first/bowel-first approach in terms of avoiding two surgeries, expediting the start of chemotherapy, and lowering the risk of cancer dissemination, postoperative complications and increased surgical stress are still a concern [2729].

Surgical treatment for lung metastases and peritoneal metastases is developing in addition to liver metastases. Surgery can be beneficial for pulmonary metastasis, a metastatic lesion that is similar to liver metastasis in terms of how well it responds to treatment [30,31]. A five-year OS rate of more than 50% was observed after pulmonary metastasectomy in a systematic analysis of surgical removal of pulmonary metastases in CRC patients [31]. Now, pulmonary oligo-metastasis and solitary lesions are frequently treated with video-assisted thoracoscopic surgery. In a recent meta-analysis, there was no discernible difference in the rates of OS and recurrence-free survival between open thoracotomy and video-assisted thoracoscopic surgery for pulmonary metastasectomy [32]. Additionally, SBRT is beginning to show promise in the management of lung metastases. The examination of a sizable multi-center database revealed that OS was enhanced by SBRT for oligo-metastatic CRC. Retrospective analysis of 381 oligo-metastatic CRC lesions in 235 CRC patients revealed that those who underwent SBRT had two-year OS rates of 76.1% and five-year OS rates of 35.9% [21,33]. The advancement of non-surgical local therapy benefits the active management of lung metastases as well.

It is known that peritoneal metastasis occurs in about 5%–15% of CRC patients, and the metastasis of CRC is known to have the worst prognosis [16]. Surgery has a very small part in the management of peritoneal metastases; the primary therapy is palliative chemotherapy. However, the role of surgery has been consistently examined in patients with limited peritoneal metastases, and efforts to increase the survival rate have persisted through active treatment with cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) [16,3436] (Fig. 2). In some patients with peritoneal metastases, CRS/HIPEC may enhance oncological outcomes, according to long-term randomized controlled trials and meta-analyses [35,36]. Effectiveness of HIPEC has been questioned, though, with the advent of systemic chemotherapy [37], and it is thought that this is due to resistance to the anticancer medications that are currently being employed. As a result, progress in treating metastatic CRC, particularly in raising the survival rate, has stalled. Instead, doctors are still choosing anticancer drugs that are sensitive to the disease and using precision medicine when it is necessary. It appears to be a solution for the treatment of peritoneal metastasis [38]. In order to effectively treat metastatic CRC in the future, new medications will need to be created and used, with treatment decisions based on more precise genetic data. In addition, the role of sophisticated multidisciplinary treatment involving professionals will be critical for improving oncological outcomes in order to increase the potential of curing as well as controlling the disease by performing surgical treatment and other local treatments at the right moment.

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Fig. 2. Cytoreductive surgery for patients with peritoneal carcinomatosis from colorectal cancer. Peritoectomy process at (A) pelvic cavity, (B) left upper quadrant, (C) intestinal organs, (D) and small bowel mesentery. Adapted from Kim and Kim 2021 [16] with CC-BY-NC.
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Paradigm Shift of Rectal Cancer Treatment

Neoadjuvant chemoradiotherapy (nCRT) altered the idea of surgical excision in the treatment of rectal cancer. Surgery has always been and continues to be regarded as the most crucial and necessary step for cure of CRC [39]. Although it is known that there is no change in the OS or recurrence-free survival rates when compared to postoperative radiation therapy or surgical resection alone, radiation therapy prior to rectal cancer surgery boosts the full resection rate of rectal cancer and lowers the local recurrence rate [40]. Despite this drawback, finding total or nearly complete rectal cancer regression to nCRT allowed even individuals with early-stage advanced rectal cancer to use an organ-preserving method. Although radical resection of rectal cancer has improved functional outcomes and greater sphincter preservation due to technical advancements [41,42], organ preservation strategies have grown in popularity due to its obvious functional benefits when compared to oncologic outcomes [4345]. When the results of representative trials, which showed good oncologic outcomes following organ preservation [44,45], were compared to the outcomes of radical resection for patients who respond well to nCRT, interest in organ preservation of rectal cancer has sharply increased. Many initiatives have been made in an effort to increase the number of patients who fully respond to nCRT. The greatest barrier to incorporating organ preservation techniques into actual clinical practice, meanwhile, continues to be the poor accuracy of response evaluation to nCRT. It also has to do with the diagnosis of local regrowth, a rare variation of local recurrence in rectal cancer treated with organ preservation techniques. However, the salvage percentage for these patients was observed to vary [46,47]. Local regrowth occurred in 20%–30% of patients who undergo organ preservation [4446]. In this context, we must be careful not to reduce the likelihood of a cure by improperly implementing an organ preservation strategy.

In the era of advanced rectal cancer treatment, trials to enhance distant metastasis control are ongoing, along with enhancing quality of life by including comprehensive neoadjuvant treatment (TNT) [48,49]. TNT, however, has not yet demonstrated any advantages in terms of controlling distant metastases, although showing a rise in clinical near-complete responders. After nCRT, distant metastasis is still a significant oncologic issue, therefore we need to wait and critically examine long-term results [50]. The emphasis on striking a balance between quality of life and oncologic outcomes for the treatment of rectal cancer will continue.

Conclusion

A significant cancer subtype that continues to endanger public health is CRC. Although the screening program is now run well, there is ongoing concern about how to increase compliance and practically apply non-invasive tests. The screening program must be revised to reflect epidemiologic shift as the prevalence of young-age CRC grew and, on the other hand, elderly CRC patients increased due to an increase in life expectancy. Physicians and patients are more interested in finding ways to balance quality of life and oncologic outcomes, and surveillance is more crucial to find cancer as early as feasible in order to preserve function without impairing oncologic results.

Active treatment for metastatic CRC has been carried out to break the CRC survival plateau. The role of surgical treatment has increased for metastatic CRC along with systemic treatment and targeted treatment based on genomic features of individuals. On the other hand, one of the most significant changes in the period of surgical therapy of CRC is the judicious deferral of surgical treatment, including nCRT/TNT.

The overall trend in CRC treatment is toward precision medicine, which protects the patient's quality of life while also ensuring the best oncological treatment outcomes by taking into account the patient's unique traits, way of life, and genetic characteristics. As a result, the trend in treatment showed development at both ends: for rectal cancer, which responds well to neoadjuvant therapy, efforts are rising in the direction of organ preservation, and for metastatic CRC, which had previously undergone rather harsh treatment. It will be able to offer a new development direction for CRC treatment when the financial support to move from the current standard, which concentrated on standard treatment to enhance the overall treatment outcome, to precision treatment and the improvement of the system come together.

Acknowledgements

Not applicable.

Conflict of Interest

No potential conflict of interest relevant to this article was reported.

Author Contribution

The article is prepared by a single author.

Ethics Approval and Consent to Participate

Not applicable.

References

1.

Kang MJ, Won YJ, Lee JJ, Jung KW, Kim HJ, Kong HJ, et al. Cancer statistics in Korea: incidence, mortality, survival, and prevalence in 2019. Cancer Res Treat 2022; 54(2):330-344

2.

Sung H, Ferlay J, Siegel RL, Laversanne M, Soerjomataram I, Jemal A, et al. Global cancer statistics 2020: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries. CA Cancer J Clin 2021; 71(3):209-249

3.

Nam S, Kim D, Jung K, Choi YJ, Kang JG. Analysis of the incidence and clinical features of colorectal nonadenocarcinoma in Korea: a national cancer registry-based study. Ann Coloproctol 2020; 36(6):390-397

4.

Lee SM, Shin JS. Colorectal cancer in octogenarian and nonagenarian patients: clinicopathological features and survivals. Ann Coloproctol 2020; 36(5):323-329

5.

Siegel RL, Miller KD, Sauer AG, Fedewa SA, Butterly LF, Anderson JC, et al. Colorectal cancer statistics, 2020. CA Cancer J Clin 2020; 70(3):145-164

6.

Shaukat A, Kahi CJ, Burke CA, Rabeneck L, Sauer BG, Rex DK. ACG clinical guidelines: colorectal cancer screening 2021. Am J Gastroenterol 2021; 116(3):458-479

7.

Sohn DK, Kim MJ, Park Y, Suh M, Shin A, Lee HY, et al. The Korean guideline for colorectal cancer screening. J Korean Med Assoc 2015; 58(5):420-432

8.

Imperiale TF, Ransohoff DF, Itzkowitz SH, Turnbull BA, Ross ME. Fecal DNA versus fecal occult blood for colorectal-cancer screening in an average-risk population. N Engl J Med 2004; 351(26):2704-2714

9.

Alhadi SC, Zain WZW, Zahari Z, Hashim MNM, Aziz SHSA, Zakaria Z, et al. The use of M2-pyruvate kinase as a stool biomarker for detection of colorectal cancer in tertiary teaching hospital: a comparative study. Ann Coloproctol 2020; 36(6):409-414

10.

Han YD, Oh TJ, Chung TH, Jang HW, Kim YN, An S, et al. Early detection of colorectal cancer based on presence of methylated syndecan-2 (SDC2) in stool DNA. Clin Epigenetics 2019; 11(1):51

11.

Meester RGS, Peterse EFP, Knudsen AB, de Weerdt AC, Chen JC, Lietz AP, et al. Optimizing colorectal cancer screening by race and sex: microsimulation analysis II to inform the American Cancer Society colorectal cancer screening guideline. Cancer 2018; 124(14):2974-2985

12.

Liang PS, Allison J, Ladabaum U, Martinez ME, Murphy CC, Schoen RE, et al. Potential intended and unintended consequences of recommending initiation of colorectal cancer screening at age 45 years. Gastroenterology 2018; 155(4):950-954

13.

Mannucci A, Zuppardo RA, Rosati R, Leo MD, Perea J, Cavestro GM. Colorectal cancer screening from 45 years of age: thesis, antithesis and synthesis. World J Gastroenterol 2019; 25(21):2565-2580

14.

Imperiale TF, Kahi CJ, Rex DK. Lowering the starting age for colorectal cancer screening to 45 years: who will come… and should they?. Clin Gastroenterol Hepatol 2018; 16(10):1541-1544

15.

US Preventive Services Task Force. Screening for colorectal cancer US preventive services task force recommendation statement. J Am Med Assoc 2021; 325(19):1965-1977

16.

Kim YJ, Kim CH. Treatment for peritoneal metastasis of patients with colorectal cancer. Ann Coloproctol 2021; 37(6):425-433

17.

Choti MA, Sitzmann JV, Tiburi MF, Sumetchotimetha W, Rangsin R, Schulick RD, et al. Trends in long-term survival following liver resection for hepatic colorectal metastases. Ann Surg 2002; 235(6):759-766

18.

Torky R, Alessa M, Kim HS, Sakr A, Zakarneh E, Sauri F, et al. Characteristics of patients presented with metastases during or after completion of chemoradiation therapy for locally advanced rectal cancer: a case series. Ann Coloproctol 2021; 37(3):186-191

19.

Ruers T, Punt C, Van Coevorden F, Pierie JPEN, Borel-Rinkes I, Ledermann JA, et al. Radiofrequency ablation combined with systemic treatment versus systemic treatment alone in patients with non-resectable colorectal liver metastases: a randomized EORTC Intergroup phase II study (EORTC 40004). Ann Oncol 2012; 23(10):2619-2626

20.

Chow FCL, Chok KSH. Colorectal liver metastases: an update on multidisciplinary approach. World J Hepatol 2019; 11(2):150-172

21.

Sheikh S, Chen H, Sahgal A, Poon I, Erler D, Badellino S, et al. An analysis of a large multi-institutional database reveals important associations between treatment parameters and clinical outcomes for stereotactic body radiotherapy (SBRT) of oligometastatic colorectal cancer. Radiother Oncol 2022; 167:187-194

22.

Nakamura Y, Hokuto D, Koyama F, Matsuo Y, Nomi T, Yoshikawa T, et al. The prognosis and recurrence pattern of right- and left-sided colon cancer in stage II, stage III, and liver metastasis after curative resection. Ann Coloproctol 2021; 37(5):326-336

23.

Choti MA, Sitzmann JV, Tiburi MF, Sumetchotimetha W, Rangsin R, Schulick RD, et al. Trends in long-term survival following liver resection for hepatic colorectal metastases. Ann Surg 2002; 235(6):759-766

24.

Park SH, Shin JK, Lee WY, Yun SH, Cho YB, Huh JW, et al. Clinical outcomes of neoadjuvant chemotherapy in colorectal cancer patients with synchronous resectable liver ketastasis: a propensity score matching analysis. Ann Coloproctol 2021; 37(4):244-252

25.

Sandström P, Røsok BI, Sparrelid E, Larsen PN, Larsson AL, Lindell G, et al. ALPPS improves resectability compared with conventional two-stage hepatectomy in patients with advanced colorectal liver metastasis: results from a Scandinavian multicenter randomized controlled trial (LIGRO trial). Ann Surg 2018; 267(5):833-840

26.

Hasselgren K, Røsok BI, Larsen PN, Sparrelid E, Lindell G, Schultz NA, et al. ALPPS improves survival compared with TSH in patients affected of CRLM: survival analysis from the randomized controlled trial LIGRO. Ann Surg 2021; 273(3):442-448

27.

Vallance AE, van der Meulen J, Kuryba A, Charman SC, Botterill ID, Prasad KR, et al. The timing of liver resection in patients with colorectal cancer and synchronous liver metastases: a population-based study of current practice and survival. Colorectal Dis 2018; 20(6):486-495

28.

Slesser AAP, Simillis C, Goldin R, Brown G, Mudan S, Tekkis PP. A meta-analysis comparing simultaneous versus delayed resections in patients with synchronous colorectal liver metastases. Surg Oncol 2013; 22(1):36-47

29.

Brouquet A, Mortenson MM, Vauthey JN, Rodriguez-Bigas MA, Overman MJ, Chang GJ, et al. Surgical strategies for synchronous colorectal liver metastases in 156 consecutive patients: classic, combined or reverse strategy?. J Am Coll Surg 2010; 210(6):934-941

30.

Kim JY, Park IJ, Kim HR, Kim DK, Lee JL, Yoon YS, et al. Post-pulmonary metastasectomy prognosis after curative resection for colorectal cancer. Oncotarget 2017; 8:36566-36577

31.

Pfannschmidt J, Dienemann H, Hoffmann H. Surgical resection of pulmonary metastases from colorectal cancer: a systematic review of published series. Ann Thorac Surg 2007; 84(1):324-338

32.

Meng D, Fu L, Wang L, Dai Y, Lv W, Zhang J, et al. Video-assisted thoracoscopic surgery versus open thoracotomy in pulmonary metastasectomy: a meta-analysis of observational studies. Interact Cardiovasc Thorac Surg 2016; 22(2):200-206

33.

Mitry E, Guiu B, Cosconea S, Jooste V, Faivre J, Bouvier AM. Epidemiology, management and prognosis of colorectal cancer with lung metastases: a 30-year population-based study. Gut 2010; 59(10):1383-1388

34.

Roh SJ, Park SC, Choi J, Lee JS, Lee DW, Hong CW, et al. Cytoreductive surgery and hyperthermic intraperitoneal chemotherapy with mitomycin C used for colorectal peritoneal carcinomatosis. Ann Coloproctol 2020; 36(1):22-29

35.

Goéré D, Glehen O, Quenet F, Guilloit JM, Bereder JM, Lorimier G, et al. Second-look surgery plus hyperthermic intraperitoneal chemotherapy versus surveillance in patients at high risk of developing colorectal peritoneal metastases (PROPHYLOCHIP-PRODIGE 15): a randomised, phase 3 study. Lancet Oncol 2020; 21(9):1147-1154

36.

Klaver CEL, Wisselink DD, Punt CJA, Snaebjornsson P, Crezee J, Aalbers AGJ, et al. Adjuvant hyperthermic intraperitoneal chemotherapy in patients with locally advanced colon cancer (COLOPEC): a multicentre, open-label, randomised trial. Lancet Gastroenterol Hepatol 2019; 4(10):761-770

37.

Quénet F, Elias D, Roca L, Goéré D, Ghouti L, Pocard M, et al. Cytoreductive surgery plus hyperthermic intraperitoneal chemotherapy versus cytoreductive surgery alone for colorectal peritoneal metastases (PRODIGE 7): a multicentre, randomised, open-label, phase 3 trial. Lancet Oncol 2021; 22(2):256-266

38.

Mendelaar PAJ, Smid M, van Riet J, Angus L, Labots M, Steeghs N, et al. Whole genome sequencing of metastatic colorectal cancer reveals prior treatment effects and specific metastasis features. Nat Commun 2021; 12:3269

39.

Varela C, Kim NK. Surgical treatment of low-lying rectal cancer: updates. Ann Coloproctol 2021; 37(6):395-424

40.

Sauer R, Liersch T, Merkel S, Fietkau R, Hohenberger W, Hess C, et al. Preoperative versus postoperative chemoradiotherapy for locally advanced rectal cancer: results of the German CAO/ARO/AIO-94 randomized phase III trial after a median follow-up of 11 years. J Clin Oncol 2012; 30(16):1926-1933

41.

Piozzi GN, Kim SH. Robotic intersphincteric resection for low rectal cancer: technical controversies and a systematic review on the perioperative, oncological, and functional outcomes. Ann Coloproctol 2021; 37(6):351-367

42.

Eldamshety O, Kotb S, Khater A, Roshdy S, Elnahas W, Zahi MS, et al. Early and late functional outcomes of anal sphincter-sparing procedures with total mesorectal excision for anorectal adenocarcinoma. Ann Coloproctol 2020; 36(3):148-154

43.

Huh JW, Maeda K, Liu Z, Wang X, Roslani AC, Lee WY. Current status of “Watch-and-Wait” rectal cancer treatment in Asia-Pacific countries. Ann Coloproctol 2020; 36(2):70-77

44.

Garcia-Aguilar J, Patil S, Kim JK, Yuval JB, Thompson H, Verheij F, et al. Preliminary results of the organ preservation of rectal adenocarcinoma (OPRA) trial. J Clin Oncol 2020; 38:4008

45.

Dossa F, Chesney TR, Acuna SA, Baxter NN. A watch-and-wait approach for locally advanced rectal cancer after a clinical complete response following neoadjuvant chemoradiation: a systematic review and meta-analysis. Lancet Gastroenterol Hepatol 2017; 2(7):501-513

46.

van der Valk MJM, Hilling DE, Bastiaannet E, Meershoek-Klein Kranenbarg E, Beets GL, Figueiredo NL, et al. Long-term outcomes of clinical complete responders after neoadjuvant treatment for rectal cancer in the International Watch & Wait Database (IWWD): an international multicentre registry study. Lancet 2018; 391(10139):2537-2545

47.

Kong JC, Guerra GR, Warrier SK, Ramsay RG, Heriot AG. Outcome and salvage surgery following "Watch and Wait" for rectal cancer after neoadjuvant therapy: a systematic review. Dis Colon Rectum 2017; 60(3):335-345

48.

Giunta EF, Bregni G, Pretta A, Deleporte A, Liberale G, Bali AM, et al. Total neoadjuvant therapy for rectal cancer: making sense of the results from the RAPIDO and PRODIGE 23 trials. Cancer Treat Rev 2021; 96:102177

49.

Bahadoer RR, Dijkstra EA, van Etten B, Marijnen CAM, Putter H, Kranenbarg EM, et al. RAPIDO collaborative investigators. Short-course radiotherapy followed by chemotherapy before total mesorectal excision (TME) versus preoperative chemoradiotherapy, TME, and optional adjuvant chemotherapy in locally advanced rectal cancer (RAPIDO): a randomised, open-label, phase 3 trial. Lancet Oncol 2021; 22(1):29-42

50.

Oh SG, Park IJ, Seo J, Kim YI, Lim SB, Kim CW, et al. Beware of early relapse in rectal cancer patients treated with preoperative chemoradiotherapy. Ann Coloproctol 2020; 36(6):382-389