The standard treatment approach of localized rectal adenocarcinoma involves neoadjuvant radiotherapy and chemotherapy followed by assessment for surgery and optional adjuvant chemotherapy. However, such patients who achieve complete of near complete clinical response after neoadjuvant therapy are increasingly being managed with the 'Watch-and-Wait strategy' in the recent years. Although safety of such policy has been established, the patient population in the published studies are not represented well by Asian population. Moreover, the data about safety of such policy in the setting of modern neoadjuvant strategies is limited. The Principle Investigator propose a multinational collaborative prospective database study in Asia to systematically collect data on patients being managed with such a strategy. The target population is patients with localized rectal adenocarcinoma achieving near complete or complete response being managed by the Watch-and-Wait strategy. The primary end point being local regrowth and other survival and quality of life end points will be evaluated as well. A secure multinational database will be generated over 5 years with an estimated expected minimal sample size of 337 patients over 5 years across 7-10 Asian institutes to precisely evaluate the required endpoints. Ethical and legal requirements will be met at each participating institute.

Neoadjuvant radiation and chemotherapy followed by total mesorectal excision (TME) remains a standard approach in most of the centres globally. Although the oncological outcomes have improved significantly with this multimodality approach over the last few decades, this approach adversely affects quality of life and functional outcomes especially for those needing permanent colostomy. More recently, patients achieving complete or near complete response are increasingly being managed by the 'Watch-and-Wait' approach where in, patients are followed using an intense follow up protocol after radiation and chemotherapy and avoid or delay surgery(1)(2)(3)(4)(5). However, this approach has not been widely adopted worldwide and there is limited data in the published medical literature. While the randomized trials in this setting does not appear to be feasible for obvious ethical reasons, robust data collected both retrospectively and prospectively can provide insights into this approach and help us refine the Watch-and-Wait approach in our routine clinics and in optimizing patient selection and surveillance strategies. Such an attempt was done by developing a multinational database from the Netherlands, Brazil, Portugal, and the UK(6). This data base consisted of more than a thousand patients and several important clinical questions were answered using this data(7)(8). However, this database largely consisted of patients treated using long course chemoradiation which was considered a standard treatment previously at that time. Moreover, there was no representation from Asian countries in this database. Currently, with the recent publications from the large, randomized trials like RAPIDO, UNICANCER PRODIGE 23, OPRA, more and more patients with locally advanced non-metastatic rectal adenocarcinoma are managed with a total neoadjuvant therapy approach(9)(10)(11). Radiotherapy dose escalation using brachytherapy has also gained interest with recent publication of results from the OPERA trial(12). Hence, with these developments, management practice of locally advanced rectal adenocarcinomas has become heterogeneous across institutions globally. These patients are being treated with more aggressive neoadjuvant therapies including total neoadjuvant therapy (TNT) approach. Many of these regimens involve multiagent neoadjuvant chemotherapy in addition to chemoradiation or short course hypofractionated radiotherapy leading increased response rates. The knowledge about the risks and benefits of watch-and-wait strategy after newer neoadjuvant strategies is somewhat limited. It is not entirely known whether the watch-and-wait approach can be applied safely to these patients who achieve clinical complete response after more aggressive neoadjuvant therapy regimens. Also, the data on Asian patients managed with such a strategy is scarce in the literature. Not only the inherent biological and genetic factors associated with rectal adenocarcinoma in Asian patients may be different but also the compliance and feasibility of intense surveillance protocol can be challenging in some of the Asian countries. Considering all these, the principle investigator intend to develop a comprehensive and secure database exclusively from Asian countries and to collect meaningful data systematically to answer important clinical questions on watch-and-wait strategy in Asian patients. This effort is likely to strengthen available evidence on this subject and generate evidence based on data exclusively from Asian patients. Collective efforts from participating nations can facilitate mutual learning and help in safe adoption of the watch-and-wait strategy in a greater number of centres across Asia. This collaborative study among Asian countries may potentially pave the way for future studies of similar kind.

Inclusion Criteria:

• Histologically confirmed diagnosis of adenocarcinoma of the rectum
• Age ≥18 years
• Clinical stage T1-T4, N0-N2, M0 at diagnosis
• ECOG Performance status 0-1
• Neoadjuvant treatment with either short course or long course radiation therapy and / or chemotherapy
• Complete or near complete clinical response after neoadjuvant therapy
• Patients willing to be on watch-and-wait strategy.
• The distance from anal verge of tumor up to 10 cm (Mid and low rectal tumors)

Exclusion Criteria:

• Recurrent rectal cancer
• Patients with any other concurrent medical or psychiatric condition or disease which would make them inappropriate candidates for entry into this study.
• Not willing to consent for the study or to follow up routinely
• Patients who cannot read or understand the language of QoL

Patients with localized rectal adenocarcinoma being treated at hospitals or institutes