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Background Although self‐expandable metal stent (SEMS) placement as bridge to surgery (BTS) in patients with left‐sided obstructing colonic cancer has shown promising short‐term results, it is used infrequently owing to uncertainty about its oncological safety. This population study compared long‐term oncological outcomes between emergency resection and SEMS placement as BTS. Methods Through a national collaborative research project, long‐term outcome data were collected for all patients who underwent resection for left‐sided obstructing colonic cancer between 2009 and 2016 in 75 Dutch hospitals. Patients were identified from the Dutch Colorectal Audit database. SEMS as BTS was compared with emergency resection in the curative setting after 1 : 2 propensity score matching. Results Some 222 patients who had a stent placed were matched to 444 who underwent emergency resection. The overall SEMS‐related perforation rate was 7·7 per cent (17 of 222). Three‐year locoregional recurrence rates after SEMS insertion and emergency resection were 11·4 and 13·6 per cent (P = 0·457), disease‐free survival rates were 58·8 and 52·6 per cent (P = 0·175), and overall survival rates were 74·0 and 68·3 per cent (P = 0·231), respectively. SEMS placement resulted in significantly fewer permanent stomas (23·9 versus 45·3 per cent; P < 0·001), especially in elderly patients (29·0 versus 57·9 per cent; P < 0·001). For patients in the SEMS group with or without perforation, 3‐year locoregional recurrence rates were 18 and 11·0 per cent (P = 0·432), disease‐free survival rates were 49 and 59·6 per cent (P = 0·717), and overall survival rates 61 and 75·1 per cent (P = 0·529), respectively. Conclusion Overall, SEMS as BTS seems an oncologically safe alternative to emergency resection with fewer permanent stomas. Nevertheless, the risk of SEMS‐related perforation, as well as permanent stoma, might influence shared decision‐making for individual patients.

482 Background: Patients with T4 or perforated colon cancer are at high risk (~25%) of peritoneal metastases (PM). Sensitivity of imaging modalities for PM is limited and the majority of patients is diagnosed in a palliative setting. This provides a rationale for adjuvant hyperthermic intraperitoneal chemotherapy (HIPEC). In this study, the effectiveness of adjuvant HIPEC in reducing the risk of PM was determined. Methods: In this multicenter trial, patients with T4 (either cT4 or pT4, N0-2, M0) or perforated colon cancer, who underwent curative resection were randomized to adjuvant HIPEC followed by routine adjuvant systemic chemotherapy or to adjuvant systemic chemotherapy alone (1:1). Adjuvant HIPEC with oxaliplatin was performed simultaneously (9%) or within five-eight weeks (91%) after the primary tumor resection. Patients without evidence of recurrent disease at 18 months based on CT imaging underwent diagnostic laparoscopy in both arms. The primary endpoint was PM free survival (PMFS) at 18 months using Kaplan Meier analysis. Results: Between April 2015 and January 2017, 204 patients were randomized: 102 in the control arm (0 drop-outs), 102 in the experimental arm (two drop-outs). Surgical exploration at the start of the HIPEC procedure at five-eight weeks postoperatively revealed metastases in 11 patients (PM in 9/11) in the experimental arm, and adjuvant HIPEC was not applied. Adjuvant systemic chemotherapy was administered in 89/100 eligible patients after median 6 weeks (IQR 5-7) in the control arm and in 84/89 after 10 weeks (IQR 9-12) in the experimental arm. PM rate after completion of 18 months follow-up was 22/102 and 18/100, respectively. In the ITT analysis no difference in 18 months PMFS was observed: 77% (control) versus 81% (experimental), HR 0.836 (0.489-1.428)). Also, no differences were observed in 18 months DFS (HR 1.016 (0.646-1.598)) and OS (HR 1.139 (0.532-2.439)). One patient developed encapsulating peritoneal sclerosis after HIPEC. Conclusions: Adjuvant HIPEC with oxaliplatin for patients with T4 or perforated colon cancer does not result in improved 18 months PMFS. Long-term results have to be awaited to assess the role of HIPEC in the adjuvant setting. Clinical trial information: NCT02231086.

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