Supplemental Oxygen - Effect on Occurrence of Subsequent Cancer After Abdominal Surgery (Follow-up of the PROXI Trial)

Study Overview
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Brief Summary
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Aim: to investigate the effect of a high inspiratory oxygen fraction (FiO2) given during and after laparotomy procedures on occurrence of a subsequent, new or recurrent, cancer diagnosis at a long-term follow-up. Background: A high inspiratory oxygen fraction (FiO2 = 0.80) has been linked to prevention of surgical site infection, but the Danish randomized clinical multicenter trial, the PROXI trial, found no difference in frequency of surgical site infection. In fact, long-term mortality was significantly increased with a hazards ratio of 1.30 in patients receiving 80% oxygen, and this appeared to be statistically significant in patients undergoing cancer surgery, but not in non-cancer patients. At this point, no convincing mechanism explains the observed increased mortality after hyperoxia, as the long-term pathophysiological effects of oxygen are not fully understood. Primary hypothesis of this follow-up study of the PROXI trial: Use of 80% oxygen increase the frequency of patients with a subsequent, new or recurrent, cancer.

Official Title
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Perioperative Inspiratory Oxygen Fraction - Effect on Occurrence of Subsequent Cancer After Abdominal Surgery (Follow-up of the PROXI Trial)

Conditions
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Laparotomy

Intervention / Treatment
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* Drug: Oxygen


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Age 18 years or older. Laparotomy, acute or elective. In case of gynaecological surgery only if malignancy is suspected (defined as risk of ovarian malignancy index >200 or a specimen with atypical or neoplastic cells). Exclusion Criteria: Other surgery within 30 days (except surgery in local anaesthesia). Chemotherapy within 3 months. Inability to give informed consent. Inability to keep oxygen saturation above 90% without supplemental oxygen (measured preoperatively by pulse oximetry).

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| 80% oxygen group<br> | Drug: Oxygen<br>* During and 2 hrs after surgery<br>|
| 30% oxygen group<br> | Drug: Oxygen<br>* During and 2 hrs after surgery<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Frequency of patients with the composite outcome measure of either a subsequent, new or recurrent, cancer registration or a new histological specimen showing any neoplasm |  | 36-60 months after randomization | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Frequency of patients with subsequent, new or recurrent, cancer registration at the Danish Cancer Registry |  | 15-39 months after randomization | 
| Frequency of patients with new histological specimen in the Danish Patobank showing any neoplasm |  | 36-60 months after randomization | 
| Frequency of patients with new histological specimen in the Danish Patobank showing neoplasm of a histological type not previously diagnosed |  | 36-60 months after randomization | 
| Frequency of patients with cancer as diagnosis code at a readmission |  | 36-60 months after randomization | 
| Frequency of patients with cancer as primary diagnosis code at a readmission |  | 36-60 months after randomization | 
| Duration of cancer-free survival, as assessed by Kaplan-Meier statistics |  | 36-60 months after randomization |