Design
The TV-LARK trial is a multicentre randomised phase III superiority trial initiated by the rectal cancer research group in the Seoul National University Hospital. A list of all participating centres has been added as a supplementary file. Eligible patients were randomly assigned to receive either short-course radiotherapy and neoadjuvant chemotherapy followed by surgery (intervention; arm A) or neoadjuvant CRT followed by surgery and adjuvant chemotherapy (comparator; arm B) (Fig.1). Randomisation in a 1:1 ratio was performed centrally using a web-based system, with stratification according to clinical T (cT2-3 vs. cT4) and N (cN0 vs. cN+) stage.
Study population
Patients are eligible if they have histologically confirmed resectable stage II or III rectal adenocarcinoma without distant metastases, including para-aortic lymph nodes (LNs) and common and external iliac LN metastases. Resectability was assessed by a multiphase computed tomography (CT) scan within four weeks before randomisation. The inclusion criteria were a tumour located ≤10 cm from the anal verge, patient aged 19-80 years, Eastern Cooperative Oncology Group (ECOG) performance status scale ≤1, American Society of Anesthesiologists (ASA) class I or II, no history of any other systemic treatment or radiotherapy for rectal cancer, no history of intraoperative radiotherapy, adequate bone marrow function (i.e. absolute neutrophils ≥1,500/mm3; platelets ≥75,000/mm3), adequate liver function (bilirubin ≤2.0 fold of upper limit of normal, liver function enzymes level (aspartate aminotransferase, alanine aminotransferase) ≤2.5 fold of upper limit of normal), and adequate renal function (creatinine ≤1.5 fold of upper limit of normal or renal filtrate rate (Ccr, calculated using Cockcroft formula) ≥50 ml/min. Patients who can comply with the study protocol for the duration of the study, understand the study process and treatment plan, and have signed the informed consent form will be included.
The exclusion criteria were other malignancies within five years except for cured superficial skin cancer or cervical carcinoma in situ; prior treatment for rectal cancer; history of organ transplant requiring immunosuppressive therapy; uncontrolled epilepsy or psychosis; hypersensitivity to fluoropyrimidine agents, platinum, leucovorin, capecitabine, or confirmed dihydropyridine dehydrogenase deficiency; and genetic problems such as galactose intolerance, Lapp lactase deficiency, or glucose-galactose malabsorption. Patients who were required to continue concomitant treatment and were expected to receive oxaliplatin, flucytosine, phenytoin, or warfarin were also excluded. Furthermore, patients were ineligible in cases of National Cancer Institute Common Toxicity Criteria grade 1 or higher peripheral neuropathy, uncontrolled or severe cardiovascular disease, infection, and pregnancy.
Ethics approval and consent to participate
This study was approved by the Institutional Review Board (IRB) of Seoul National University Hospital, National Cancer Centre, Seoul Metropolitan Government Seoul National University Boramae Medical Centre, Keimyung University Dongsan Medical Centre, and Ewha Womans University Hospital (IRB no.: H-2111-046-1271, NCC2022-0098, 30-2022-20, DSMC2022-01-061, and SEUMC2022-01-028, repectively). Written informed consent will be obtained from all patients for trial participation, data acquisition, and use of clinical data before enrolment. This study was conducted in accordance with the tenets of the Declaration of Helsinki. This study will be monitored by an independent data and safety committee.
Treatment
Arm A: total neoadjuvant short-course radiotherapy followed by CAPOX (TNT group)
The treatment in arm A started with short-course radiotherapy (25 Gy in 5 fractions during a week). A topical simultaneous integrated boost was permitted at the investigator’s discretion. The contouring of the radiotherapy plan was the same as that of the control group. Neoadjuvant chemotherapy will be given within two weeks after the last radiotherapy fraction but should be within at least three weeks. Chemotherapy consisted of four cycles of CAPOX (capecitabine 1,000 mg/m2 orally twice daily on days 1-14, oxaliplatin 130 mg/m2 intravenously on day 1, and a chemotherapy-free interval between days 15- and 21). The dose was adjusted based on the maximum graded toxicity within the previous cycle. Within a week after the last day of neoadjuvant chemotherapy, restaging CT scan, MRI, and sigmoidoscopy were performed and, when appropriate, followed by surgery with curative intent. Surgery is planned 2 to 4 weeks after neoadjuvant chemotherapy. Adjuvant chemotherapy is not scheduled but can be administered at the investigator’s discretion according to the pathologic tumour response.
Arm B: neoadjuvant chemoradiotherapy and adjuvant chemotherapy (standard of care group)
Treatment in arm B starts with radiotherapy in 28 daily fractions of 1.8 Gy up to 50.4 Gy or 25 fractions up to 50.0 Gy with concomitant oral capecitabine 825 mg/m2 twice a day. In both groups, the clinical target volume (CTV) 1 was defined as an area extending 1.5 cm or more to the distal and proximal direction of the tumour in the rectum bordered by the internal iliac and presacral LNs and mesorectal fascia on CT images in the prone position. CTV 2 was defined as CTV 1 plus enlarged LN areas. Planning target volume (PRV) 1 and PTV 2 will cover 0.8-1 cm from CTV 1 and CTV 2, respectively. The radiation dose was delivered to 95 % of the PTV, and there was no area where the radiation dose is given exceeding 10 % or more than the prescribed. A three-beam technique was used, and the treating physician and hospital policy permitted intensity-modulated radiotherapy. Six weeks after the last day of CRT, a restaging examination similar to that of the TNT group was performed. Surgery was planned six - to eight weeks after the last day of CRT. Adjuvant chemotherapy was administered within 3-8 weeks after surgery. Capecitabine alone or CAPOX was administered for 3–6 months (4–8 cycles) at the investigator’s discretion. Capecitabine alone was administered at 1,250 mg/m2 twice a day on days 1-14, with three weeks per cycle. CAPOX was administered as oxaliplatin 130 mg/m2 on day 1 and capecitabine 1,250 mg/m2 twice a day on days 1-14.
Surgery: both groups
Surgery is performed according to TME principles. The rectum was dissected along the holy plane of the mesorectum. The lateral LN is additionally dissected if metastasis is suspected on preoperative MRI. Surgical approaches include laparotomy, laparoscopy, robotics, and transanal TME. Rectal preservation strategies, such as local excision or watch-and-wait, are not considered in this protocol. Postoperative complications were defined according to the Clavien-Dindo classification and recorded until 30 days after surgery. If neoadjuvant chemotherapy or radiotherapy is discontinued because of toxicity or in cases of local progression, patients will still proceed with the surgery. Patients who develop distant metastasis or unresectable disease during neoadjuvant therapy at restaging on the other hand will proceed with chemotherapy.
Outcomes
The primary endpoint was pCR, which will be evaluated by independent pathologists at each institution. Secondary endpoints included disease-related treatment failure (first occurrence of locoregional failure, new primary colorectal cancer, distant metastasis, or treatment-related death) [20], quality of life (patient-reported outcomes), and cost-effectiveness analysis. The exploratory endpoint is circulating tumour DNA (ctDNA), which will be measured to confirm whether detecting a treatment response, relapse, or relapse at an earlier phase is possible.
Follow up
After treatment, follow-up will be conducted every six months for five years. Physical exam, tumour markers (carcinoembryonic antigen [CEA] and carbohydrate antigen 19-9 [CA19-9]), and chest and abdomen CT scans will be taken every six months until disease recurrence or up to a maximum of 5 years after the end of treatment without recurrence. Total colonoscopy was planned at 12, 36, and 60 months postoperatively. Rectal MRI and PET CT scans are allowed on indication to detect or confirm recurrence.
Quality of life and functional outcomes
The quality of life and functional outcomes were assessed using patient-reported questionnaires at multiple time points throughout the treatment and during follow-up. The questionnaires included two European Organization for Research and Treatment of Cancer (EORTC) questionnaires: the quality-of-life questionnaire for patients with cancer (QLQ-C30) and the quality-of-life questionnaire for patients with colorectal cancer (QLQ-CR29). Postoperative bowel function was measured using the low anterior resection syndrome (LARS) score. These questionnaires are available in Korea and have been validated in previous studies [27-29].
Sample size calculation and statistical analysis
The study hypothesis was that when the pCR rate of the conventional CRT group (arm B) was assumed to be 15%, the pCR rate will be increased to 28% in the TNT group (arm A). With a one-sided alpha of 0.025 and a power of 80%, each group needed 156 participants to prove the hypothesis. Considering the 10% of dropout rate, a total of 348 patients will be required.
Data collection and management
The web-based software iCReaT version 2.0 by the National Institute of Health of the Korean Disease Control and Prevention Agency was used for randomisation, data collection, and central data monitoring and management. Data management was coordinated by HERINGS, Co. Ltd., and clinical research coordinators of each institution collected data. Data were entered following a predefined and standardised protocol, providing guidelines for missing values. Data managers were trained using the iCReaT software and electronic case report form before data entry.
Monitoring
Qualified and independent monitoring will be performed periodically throughout the trial by HERINGS and the institutional IRB. The participating centres will be visited to randomly check the compliance with the protocol and enrolment criteria, proper treatment implementation, query review, data verification, and adverse event reports. Adverse events were graded using the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0 [30].