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Aspirin reduces the incidence of colorectal adenoma and colorectal cancer among high-risk persons. Observational studies suggest that aspirin may also improve disease-free survival after diagnosis, particularly among patients with tumors harboring somatic mutations. However, data from randomized trials are lacking. We conducted a double-blind, randomized, placebo-controlled trial involving patients with stage I, II, or III rectal cancer or stage II or III colon cancer with somatic alterations in PI3K pathway genes. The patients were assigned in a 1:1 ratio to receive 160 mg of aspirin or matched placebo once daily for 3 years. Patients with prespecified hotspot mutations in exon 9 or 20 (group A alterations) and those with other moderate- or high-impact somatic variants in , , or (group B alterations) were eligible for randomization. The primary end point was colorectal cancer recurrence, assessed in a time-to-event analysis, in patients with group A alterations. Secondary end points included colorectal cancer recurrence in patients with group B alterations, disease-free survival, and safety. Alterations in PI3K pathway genes were detected in 1103 of 2980 patients (37.0%) with complete genomic data. Of 515 patients with group A alterations and 588 patients with group B alterations, 314 and 312, respectively, were assigned to receive aspirin or placebo. The estimated 3-year cumulative incidence of recurrence was 7.7% with aspirin and 14.1% with placebo (hazard ratio, 0.49; 95% confidence interval [CI], 0.24 to 0.98; P = 0.04) among patients with group A alterations and 7.7% and 16.8%, respectively (hazard ratio, 0.42; 95% CI, 0.21 to 0.83), among those with group B alterations. The estimated 3-year disease-free survival was 88.5% with aspirin and 81.4% with placebo (hazard ratio, 0.61; 95% CI, 0.34 to 1.08) among patients with group A alterations and 89.1% and 78.7%, respectively (hazard ratio, 0.51; 95% CI, 0.29 to 0.88), among those with group B alterations. Severe adverse events occurred in 16.8% of aspirin recipients and 11.6% of placebo recipients. Aspirin led to a significantly lower incidence of colorectal cancer recurrence than placebo among patients with hotspot mutations in exon 9 or 20 and appeared to have a similar benefit among those with other somatic alterations in PI3K pathway genes. (Funded by the Swedish Research Council and others; ALASCCA ClinicalTrials.gov number, NCT02647099; EudraCT number, 2015-004240-19.).

The TME trial investigated the value of preoperative short-term radiotherapy in combination with total mesorectal excision (TME). Long-term results are reported after a median follow-up of 12 years. Between Jan 12, 1996, and Dec 31, 1999, 1861 patients with resectable rectal cancer without evidence of distant disease were randomly assigned to TME preceded by 5 × 5 Gy radiotherapy or TME alone (ratio 1:1). Randomisation was based on permuted blocks of six with stratification according to centre and expected type of surgery. The primary endpoint was local recurrence, analysed for all eligible patients who underwent a macroscopically complete local resection. 10-year cumulative incidence of local recurrence was 5% in the group assigned to radiotherapy and surgery and 11% in the surgery-alone group (p<0·0001). The effect of radiotherapy became stronger as the distance from the anal verge increased. However, when patients with a positive circumferential resection margin were excluded, the relation between distance from the anal verge and the effect of radiotherapy disappeared. Patients assigned to radiotherapy had a lower overall recurrence and when operated with a negative circumferential resection margin, cancer-specific survival was higher. Overall survival did not differ between groups. For patients with TNM stage III cancer with a negative circumferential resection margin, 10-year survival was 50% in the preoperative radiotherapy group versus 40% in the surgery-alone group (p=0·032). For all eligible patients, preoperative short-term radiotherapy reduced 10-year local recurrence by more than 50% relative to surgery alone without an overall survival benefit. For patients with a negative resection margin, the effect of radiotherapy was irrespective of the distance from the anal verge and led to an improved cancer-specific survival, which was nullified by an increase in other causes of death, resulting in an equal overall survival. Nevertheless, preoperative short-term radiotherapy significantly improved 10-year survival in patients with a negative circumferential margin and TNM stage III. Future staging techniques should offer possibilities to select patient groups for which the balance between benefits and side-effects will result in sufficiently large gains. The Dutch Cancer Society, the Dutch National Health Council, and the Swedish Cancer Society.

In a trial comparing preoperative chemoradiotherapy and FOLFOX in patients with rectal cancer undergoing sphincter-sparing surgery, 5-year disease-free survival was 80.8% with FOLFOX and 78.6% with chemoradiotherapy.

SummaryBackgroundSystemic relapses remain a major problem in locally advanced rectal cancer. Using short-course radiotherapy followed by chemotherapy and delayed surgery, the Rectal cancer And Preoperative Induction therapy followed by Dedicated Operation (RAPIDO) trial aimed to reduce distant metastases without compromising locoregional control. MethodsIn this multicentre, open-label, randomised, controlled, phase 3 trial, participants were recruited from 54 centres in the Netherlands, Sweden, Spain, Slovenia, Denmark, Norway, and the USA. Patients were eligible if they were aged 18 years or older, with an Eastern Cooperative Oncology Group (ECOG) performance status of 0–1, had a biopsy-proven, newly diagnosed, primary, locally advanced rectal adenocarcinoma, which was classified as high risk on pelvic MRI (with at least one of the following criteria: clinical tumour [cT] stage cT4a or cT4b, extramural vascular invasion, clinical nodal [cN] stage cN2, involved mesorectal fascia, or enlarged lateral lymph nodes), were mentally and physically fit for chemotherapy, and could be assessed for staging within 5 weeks before randomisation. Eligible participants were randomly assigned (1:1), using a management system with a randomly varying block design (each block size randomly chosen to contain two to four allocations), stratified by centre, ECOG performance status, cT stage, and cN stage, to either the experimental or standard of care group. All investigators remained masked for the primary endpoint until a prespecified number of events was reached. Patients allocated to the experimental treatment group received short-course radiotherapy (5 × 5 Gy over a maximum of 8 days) followed by six cycles of CAPOX chemotherapy (capecitabine 1000 mg/m 2 orally twice daily on days 1–14, oxaliplatin 130 mg/m 2 intravenously on day 1, and a chemotherapy-free interval between days 15–21) or nine cycles of FOLFOX4 (oxaliplatin 85 mg/m 2 intravenously on day 1, leucovorin [folinic acid] 200 mg/m 2 intravenously on days 1 and 2, followed by bolus fluorouracil 400 mg/m 2 intravenously and fluorouracil 600 mg/m 2 intravenously for 22 h on days 1 and 2, and a chemotherapy-free interval between days 3–14) followed by total mesorectal excision. Choice of CAPOX or FOLFOX4 was per physician discretion or hospital policy. Patients allocated to the standard of care group received 28 daily fractions of 1·8 Gy up to 50·4 Gy or 25 fractions of 2·0 Gy up to 50·0 Gy (per physician discretion or hospital policy), with concomitant twice-daily oral capecitabine 825 mg/m 2 followed by total mesorectal excision and, if stipulated by hospital policy, adjuvant chemotherapy with eight cycles of CAPOX or 12 cycles of FOLFOX4. The primary endpoint was 3-year disease-related treatment failure, defined as the first occurrence of locoregional failure, distant metastasis, new primary colorectal tumour, or treatment-related death, assessed in the intention-to-treat population. Safety was assessed by intention to treat. This study is registered with the EudraCT, 2010-023957-12, and ClinicalTrials.gov, NCT01558921, and is now complete. FindingsBetween June 21, 2011, and June 2, 2016, 920 patients were enrolled and randomly assigned to a treatment, of whom 912 were eligible (462 in the experimental group; 450 in the standard of care group). Median follow-up was 4·6 years (IQR 3·5–5·5). At 3 years after randomisation, the cumulative probability of disease-related treatment failure was 23·7% (95% CI 19·8–27·6) in the experimental group versus 30·4% (26·1–34·6) in the standard of care group (hazard ratio 0·75, 95% CI 0·60–0·95; p=0·019). The most common grade 3 or higher adverse event during preoperative therapy in both groups was diarrhoea (81 [18%] of 460 patients in the experimental group and 41 [9%] of 441 in the standard of care group) and neurological toxicity during adjuvant chemotherapy in the standard of care group (16 [9%] of 187 patients). Serious adverse events occurred in 177 (38%) of 460 participants in the experimental group and, in the standard of care group, in 87 (34%) of 254 patients without adjuvant chemotherapy and in 64 (34%) of 187 with adjuvant chemotherapy. Treatment-related deaths occurred in four participants in the experimental group (one cardiac arrest, one pulmonary embolism, two infectious complications) and in four participants in the standard of care group (one pulmonary embolism, one neutropenic sepsis, one aspiration, one suicide due to severe depression). InterpretationThe observed decreased probability of disease-related treatment failure in the experimental group is probably indicative of the increased efficacy of preoperative chemotherapy as opposed to adjuvant chemotherapy in this setting. Therefore, the experimental treatment can be considered as a new standard of care in high-risk locally advanced rectal cancer. FundingDutch Cancer Foundation, Swedish Cancer Society, Spanish Ministry of Economy and Competitiveness, and Spanish Clinical Research Network.

In a randomized trial involving more than 1000 patients, outcomes including recurrence rate and overall survival were similar among patients undergoing laparoscopic surgery and those undergoing open surgery. Colorectal cancer is the third most common cancer worldwide and accounts for nearly 1.4 million new cases and 694,000 deaths per year. Approximately one third of all colorectal cancers are localized in the rectum. 1 – 4 Less than a half century ago, rectal cancer had a poor prognosis, with cancer recurrence rates in the pelvic or perineal area (locoregional recurrence) of up to 40% and 5-year survival rates after surgical resection of less than 50%. 5 , 6 In the 1980s, Heald and Ryall 6 introduced a new surgical technique of complete removal of the fatty envelope surrounding the rectum (mesorectum), called total mesorectal . . .

The role of adjuvant chemotherapy for patients with rectal cancer is controversial, especially when used after preoperative chemoradiotherapy. Fluoropyrimidine-based adjuvant chemotherapy, including fluorouracil and leucovorin, has been widely used; however, the addition of oxaliplatin to fluorouracil and leucovorin (FOLFOX), a standard adjuvant regimen for colon cancer, has not been tested in rectal cancer. We aimed to compare the efficacy and safety of adjuvant fluorouracil and leucovorin with that of FOLFOX in patients with locally advanced rectal cancer after preoperative chemoradiotherapy. In this open-label, multicentre, phase 2, randomised trial, patients with postoperative pathological stage II (ypT3–4N0) or III (ypTanyN1–2) rectal cancer after preoperative fluoropyrimidine-based chemoradiotherapy and total mesorectal excision were recruited and randomly assigned (1:1) via a web-based software platform to receive adjuvant chemotherapy with either four cycles of fluorouracil and leucovorin (fluorouracil 380 mg/m2 and leucovorin 20 mg/m2 on days 1–5, every 4 weeks) or eight cycles of FOLFOX (oxaliplatin 85 mg/m2, leucovorin 200 mg/m2, and fluorouracil bolus 400 mg/m2 on day 1, and fluorouracil infusion 2400 mg/m2 for 46 h, every 2 weeks). Stratification factors were pathological stage (II vs III) and centre. Neither patients nor investigators were masked to group assignment. The primary endpoint was 3-year disease-free survival, analysed by intention to treat. This study is fully enrolled, is in long-term follow-up, and is registered with ClinicalTrials.gov, number NCT00807911. Between Nov 19, 2008, and June 12, 2012, 321 patients were randomly assigned to fluorouracil and leucovorin (n=161) and FOLFOX (n=160). 141 (95%) of 149 patients in the fluorouracil plus leucovorin group and 141 (97%) of 146 in the FOLFOX group completed all planned cycles of adjuvant treatment. Median follow-up was 38·2 months (IQR 26·4–50·6). 3-year disease-free survival was 71·6% (95% CI 64·6–78·6) in the FOLFOX group and 62·9% (55·4–70·4) in the fluorouracil plus leucovorin group (hazard ratio 0·657, 95% CI 0·434–0·994; p=0·047). Any grade neutropenia, thrombocytopenia, fatigue, nausea, and sensory neuropathy were significantly more common in the FOLFOX group than in the fluorouracil plus leucovorin group; however, we noted no significant difference in the frequency of these events at grade 3 or 4. The most common grade 3 or worse adverse events were neutropenia (38 [26%] of 149 patients in the fluorouracil plus leucovorin group vs 52 [36%] of 146 patients in the FOLFOX group), leucopenia (eight [5%] vs 12 [8%]), febrile neutropenia (four [3%] vs one [<1%]), diarrhoea (four [3%] vs two [1%]), and nausea (one [<1%] vs two [1%]). Adjuvant FOLFOX improves disease-free survival compared with fluorouracil plus leucovorin in patients with locally advanced rectal cancer after preoperative chemoradiotherapy and total mesorectal excision, and warrants further investigation. Korea Healthcare Technology R&D Project (South Korean Ministry of Health and Welfare).

Treatment of locally advanced rectal cancer with chemoradiotherapy, surgery, and adjuvant chemotherapy controls local disease, but distant metastases remain common. We aimed to assess whether administering neoadjuvant chemotherapy before preoperative chemoradiotherapy could reduce the risk of distant recurrences. We did a phase 3, open-label, multicentre, randomised trial at 35 hospitals in France. Eligible patients were adults aged 18–75 years and had newly diagnosed, biopsy-proven, rectal adenocarcinoma staged cT3 or cT4 M0, with a WHO performance status of 0–1. Patients were randomly assigned (1:1) to either the neoadjuvant chemotherapy group or standard-of-care group, using an independent web-based system by minimisation method stratified by centre, extramural extension of the tumour into perirectal fat according to MRI, tumour location, and stage. Investigators and participants were not masked to treatment allocation. The neoadjuvant chemotherapy group received neoadjuvant chemotherapy with FOLFIRINOX (oxaliplatin 85 mg/m2, irinotecan 180 mg/m2, leucovorin 400 mg/m2, and fluorouracil 2400 mg/m2 intravenously every 14 days for 6 cycles), chemoradiotherapy (50 Gy during 5 weeks and 800 mg/m2 concurrent oral capecitabine twice daily for 5 days per week), total mesorectal excision, and adjuvant chemotherapy (3 months of modified FOLFOX6 [intravenous oxaliplatin 85 mg/m2 and leucovorin 400 mg/m2, followed by intravenous 400 mg/m2 fluorouracil bolus and then continuous infusion at a dose of 2400 mg/m2 over 46 h every 14 days for six cycles] or capecitabine [1250 mg/m2 orally twice daily on days 1–14 every 21 days]). The standard-of-care group received chemoradiotherapy, total mesorectal excision, and adjuvant chemotherapy (for 6 months). The primary endpoint was disease-free survival assessed in the intention-to-treat population at 3 years. Safety analyses were done on treated patients. This trial was registered with EudraCT (2011-004406-25) and ClinicalTrials.gov (NCT01804790) and is now complete. Between June 5, 2012, and June 26, 2017, 461 patients were randomly assigned to either the neoadjuvant chemotherapy group (n=231) or the standard-of-care group (n=230). At a median follow-up of 46·5 months (IQR 35·4–61·6), 3-year disease-free survival rates were 76% (95% CI 69–81) in the neoadjuvant chemotherapy group and 69% (62–74) in the standard-of-care group (stratified hazard ratio 0·69, 95% CI 0·49–0·97; p=0·034). During neoadjuvant chemotherapy, the most common grade 3–4 adverse events were neutropenia (38 [17%] of 225 patients) and diarrhoea (25 [11%] of 226). During chemoradiotherapy, the most common grade 3–4 adverse event was lymphopenia (59 [28%] of 212 in the neoadjuvant chemotherapy group vs 67 [30%] of 226 patients in the standard-of-care group). During adjuvant chemotherapy, the most common grade 3–4 adverse events were lymphopenia (18 [11%] of 161 in the neoadjuvant chemotherapy group vs 42 [27%] of 155 in the standard-of-care group), neutropenia (nine [6%] of 161 vs 28 [18%] of 155), and peripheral sensory neuropathy (19 [12%] of 162 vs 32 [21%] of 155). Serious adverse events occurred in 63 (27%) of 231 participants in the neoadjuvant chemotherapy group and 50 (22%) of 230 patients in the standard-of-care group (p=0·167), during the whole treatment period. During adjuvant therapy, serious adverse events occurred in 18 (11%) of 163 participants in the neoadjuvant chemotherapy group and 36 (23%) of 158 patients in the standard-of-care group (p=0·0049). Treatment-related deaths occurred in one (<1%) of 226 patients in the neoadjuvant chemotherapy group (sudden death) and two (1%) of 227 patients in the standard-of-care group (one sudden death and one myocardial infarction). Intensification of chemotherapy using FOLFIRINOX before preoperative chemoradiotherapy significantly improved outcomes compared with preoperative chemoradiotherapy in patients with cT3 or cT4 M0 rectal cancer. The significantly improved disease-free survival in the neoadjuvant chemotherapy group and the decreased neurotoxicity indicates that the perioperative approach is more efficient and better tolerated than adjuvant chemotherapy. Therefore, the PRODIGE 23 results might change clinical practice. Institut National du Cancer, Ligue Nationale Contre le Cancer, and R&D Unicancer.

Laparoscopic surgery as an alternative to open surgery in patients with rectal cancer has not yet been shown to be oncologically safe. The aim in the COlorectal cancer Laparoscopic or Open Resection (COLOR II) trial was to compare laparoscopic and open surgery in patients with rectal cancer. A non-inferiority phase 3 trial was undertaken at 30 centres and hospitals in eight countries. Patients (aged ≥18 years) with rectal cancer within 15 cm from the anal verge without evidence of distant metastases were randomly assigned to either laparoscopic or open surgery in a 2:1 ratio, stratified by centre, location of tumour, and preoperative radiotherapy. The study was not masked. Secondary (short-term) outcomes—including operative findings, complications, mortality, and results at pathological examination—are reported here. Analysis was by modified intention to treat, excluding those patients with post-randomisation exclusion criteria and for whom data were not available. This study is registered with ClinicalTrials.gov, number NCT00297791. The study was undertaken between Jan 20, 2004, and May 4, 2010. 1103 patients were randomly assigned to the laparoscopic (n=739) and open surgery groups (n=364), and 1044 were eligible for analyses (699 and 345, respectively). Patients in the laparoscopic surgery group lost less blood than did those in the open surgery group (median 200 mL [IQR 100–400] vs 400 mL [200–700], p<0·0001); however, laparoscopic procedures took longer (240 min [184–300] vs 188 min [150–240]; p<0·0001). In the laparoscopic surgery group, bowel function returned sooner (2·0 days [1·0–3·0] vs 3·0 days [2·0–4·0]; p<0·0001) and hospital stay was shorter (8·0 days [6·0–13·0] vs 9·0 days [7·0–14·0]; p=0·036). Macroscopically, completeness of the resection was not different between groups (589 [88%] of 666 vs 303 [92%] of 331; p=0·250). Positive circumferential resection margin (<2 mm) was noted in 56 (10%) of 588 patients in the laparoscopic surgery group and 30 (10%) of 300 in the open surgery group (p=0·850). Median tumour distance to distal resection margin did not differ significantly between the groups (3·0 cm [IQR 2·0–4·8] vs 3·0 cm [1·8–5·0], respectively; p=0·676). In the laparoscopic and open surgery groups, morbidity (278 [40%] of 697 vs 128 [37%] of 345, respectively; p=0·424) and mortality (eight [1%] of 699 vs six [2%] of 345, respectively; p=0·409) within 28 days after surgery were similar. In selected patients with rectal cancer treated by skilled surgeons, laparoscopic surgery resulted in similar safety, resection margins, and completeness of resection to that of open surgery, and recovery was improved after laparoscopic surgery. Results for the primary endpoint—locoregional recurrence—are expected by the end of 2013. Ethicon Endo-Surgery Europe, Swedish Cancer Foundation, West Gothia Region, Sahlgrenska University Hospital.

Local excision is an organ-preserving treatment alternative to transabdominal resection for patients with stage I rectal cancer. However, local excision alone is associated with a high risk of local recurrence and inferior survival compared with transabdominal rectal resection. We investigated the oncological and functional outcomes of neoadjuvant chemoradiotherapy and local excision for patients with stage T2N0 rectal cancer. We did a multi-institutional, single-arm, open-label, non-randomised, phase 2 trial of patients with clinically staged T2N0 distal rectal cancer treated with neoadjuvant chemoradiotherapy at 26 American College of Surgeons Oncology Group institutions. Patients with clinical T2N0 rectal adenocarcinoma staged by endorectal ultrasound or endorectal coil MRI, measuring less than 4 cm in greatest diameter, involving less than 40% of the circumference of the rectum, located within 8 cm of the anal verge, and with an Eastern Cooperative Oncology Group performance status of at least 2 were included in the study. Neoadjuvant chemoradiotherapy consisted of capecitabine (original dose 825 mg/m2 twice daily on days 1–14 and 22–35), oxaliplatin (50 mg/m2 on weeks 1, 2, 4, and 5), and radiation (5 days a week at 1·8 Gy per day for 5 weeks to a dose of 45 Gy, followed by a boost of 9 Gy, for a total dose of 54 Gy) followed by local excision. Because of adverse events during chemoradiotherapy, the dose of capecitabine was reduced to 725 mg/m2 twice-daily, 5 days per week, for 5 weeks, and the boost of radiation was reduced to 5·4 Gy, for a total dose of 50·4 Gy. The primary endpoint was 3-year disease-free survival for all eligible patients (intention-to-treat population) and for patients who completed chemotherapy and radiation, and had ypT0, ypT1, or ypT2 tumours, and negative resection margins (per-protocol group). This study is registered with ClinicalTrials.gov, number NCT00114231. Between May 25, 2006, and Oct 22, 2009, 79 eligible patients were recruited to the trial and started neoadjuvant chemoradiotherapy. Two patients had no surgery and one had a total mesorectal excision. Four additional patients completed protocol treatment, but one had a positive margin and three had ypT3 tumours. Thus, the per-protocol population consisted of 72 patients. Median follow-up was 56 months (IQR 46–63) for all patients. The estimated 3-year disease-free survival for the intention-to-treat group was 88·2% (95% CI 81·3–95·8), and for the per-protocol group was 86·9% (79·3–95·3). Of 79 eligible patients, 23 (29%) had grade 3 gastrointestinal adverse events, 12 (15%) had grade 3–4 pain, and 12 (15%) had grade 3–4 haematological adverse events during chemoradiation. Of the 77 patients who had surgery, six (8%) had grade 3 pain, three (4%) had grade 3–4 haemorrhage, and three (4%) had gastrointestinal adverse events. Although the observed 3-year disease free survival was not as high as anticipated, our data suggest that neoadjuvant chemoradiotherapy followed by local excision might be considered as an organ-preserving alternative in carefully selected patients with clinically staged T2N0 tumours who refuse, or are not candidates for, transabdominal resection. National Cancer Institute and Sanofi-Aventis.

Neoadjuvant short-course radiotherapy combined with chemotherapy as total neoadjuvant therapy increases the pathological complete response rate for patients with locally advanced rectal cancer. The potential synergistic effects of combining radiotherapy and immunotherapy might benefit patients with locally advanced rectal cancer. We aimed to compare the efficacy and safety of short-course radiotherapy followed by capecitabine–oxaliplatin chemotherapy with or without immunotherapy as total neoadjuvant therapy in patients with locally advanced rectal cancer. SPRING-01 was a single-centre, open-label, phase 2, randomised controlled trial done at the Shandong Provincial Hospital, China. Patients were aged 18–85 years with an Eastern Cooperative Oncology Group performance status of 0–1 and had biopsy-confirmed, newly diagnosed, treatment-naive, primary, locally advanced rectal adenocarcinoma with at least one of the following features: clinical tumour stage T3–4 or greater, clinical nodal stage N1 or higher, extramural vascular invasion, mesorectal fascia involvement, or lateral lymph node metastasis. Participants were randomly assigned (1:1) to receive either sintilimab plus capecitabine–oxaliplatin or capecitabine–oxaliplatin alone. The randomisation sequence was generated using computer-generated random numbers with SAS software version 9.4, using a simple randomisation method without stratification or blocking, and allocation was concealed using opaque, sealed envelopes. Neither patients nor clinical staff were masked to treatment allocation; however, pathological assessments and data analyses were conducted in a blinded manner. Patients received short-course radiotherapy (5 × 5 Gy over 5 days) followed by six cycles of intravenous capecitabine–oxaliplatin chemotherapy (intravenous oxaliplatin 130 mg/m2 over 2 h on day 1, and oral capecitabine 1000 mg/m2 twice daily on days 1–14 of each 3-week cycle) with or without intravenous sintilimab (200 mg/m2 on day 1 of each 3-week cycle), starting 1 week after completion of radiotherapy. Total mesorectal excision surgery, was done 2–3 weeks after the completion of total neoadjuvant therapy. The primary endpoint was the pathological complete response rate in the intention-to-treat population. The trial was registered with the Chinese Clinical Trial Registry (ChiCTR2100052288). Between Oct 8, 2021, and Sept 26, 2023, 116 patients with locally advanced rectal cancer were screened, of whom 98 eligible patients were randomly assigned to the sintilimab plus capecitabine–oxaliplatin group (n=49) or the capecitabine–oxaliplatin group (n=49). 68 (69%) of 98 patients were male and 30 (31%) were female; all patients were Asian. Median follow-up was 25 months (IQR 20–32). The pathological complete response rate was significantly higher in the sintilimab plus capecitabine–oxaliplatin group than in the capecitabine–oxaliplatin group (29 [59·2%, 95% CI 45·4–72·9] vs 16 [32·7%, 19·5–45·8]; p=0·015). Postoperative complications occurred in 11 (24% [95% CI 12–37]) of 45 patients in the sintilimab plus capecitabine–oxaliplatin group and in five (11% [2–21]) of 44 in the capecitabine–oxaliplatin group. Treatment-related adverse events during neoadjuvant therapy occurred in 45 (92%) of 49 patients in the sintilimab plus capecitabine–oxaliplatin group and in 44 (90%) of 49 patients in the capecitabine–oxaliplatin group. The most common treatment-related adverse events in the sintilimab plus capecitabine–oxaliplatin group and the capecitabine–oxaliplatin group were thrombocytopenia (18 [37%] vs 26 [53%]), leukopenia (19 [39%] vs 26 [53%]), anaemia (27 [55%] vs 33 [67%]), nausea or vomiting (25 [51%] vs 27 [55%]), and diarrhoea (21 [43%] vs 24 [49%]). Grade 3–4 treatment-related adverse events were observed in 16 (33%) patients in the sintilimab plus capecitabine–oxaliplatin group and 17 (35%) patients in the capecitabine–oxaliplatin group. The most common grade 3–4 adverse event was thrombocytopenia, reported in six (12%) patients in the sintilimab plus capecitabine–oxaliplatin group and in 11 (22%) patients in the capecitabine–oxaliplatin group. Serious adverse events occurred in 15 (31%) of 49 patients in the sintilimab plus capecitabine–oxaliplatin group and in nine (18%) of 49 patients in the capecitabine–oxaliplatin group. The most common serious adverse event in both treatment groups was thrombocytopenia. One (2%) patient in the capecitabine–oxaliplatin group died from septic shock due to acute ileus. No treatment-related deaths occurred in the sintilimab plus capecitabine–oxaliplatin group. In patients with locally advanced rectal cancer, short-course radiotherapy combined with sintilimab and capecitabine–oxaliplatin as a total neoadjuvant treatment significantly increased the pathological complete response rate while maintaining manageable safety profile. These findings suggest that this regimen might be a promising neoadjuvant treatment approach for locally advanced rectal cancer. The National Natural Science Foundation of China; The Special Foundation for Taishan Scholars Program of Shandong Province; The Key Research and Development Program of Shandong Province; The Natural Science Foundation of Shandong Province; The China Postdoctoral Science Foundation; and Innovent Biologics. For the Chinese translation of the abstract see Supplementary Materials section.