Optimal Selenium for Bowel Polyps (OSCAR)

Phase 1

Completed

• Conditions: Colorectal Adenoma
• Interventions: Drug: Selenomethionine; Drug: Methylselenocysteine

• Registration Number: NCT04952129
• Lead Sponsor: University of Auckland, New Zealand

Brief Summary

New Zealand (NZ) has high bowel cancer rates, which the Bowel Screening Programme aims to reduce by early detection of bowel cancer and its precursor, adenomas (polyps). Bowel cancer and adenoma rates are higher in countries like NZ with low intake of the essential trace mineral selenium. Overseas, trials of selenium supplements reduced adenoma recurrence in people with low blood selenium, but not with high levels (where adding selenium increased health risks). Laboratory research explained this, and found certain types of selenium are safer and more effective. The optimal type and dose of selenium to use in NZ cancer prevention trials is not known.

The goal of this clinical trial is to find out how to achieve the optimal amount of body selenium in people who have had a high risk bowel adenoma removed. The main questions it aims to answer are:

* what dose of selenium taken by mouth will maximise levels of the main selenium protein in blood;

* whether one type of organic selenium is better than the other at increasing blood levels of this selenium protein;

* whether a larger dose of selenium is needed in people who start with lower blood selenium levels;

Participants will take one selenium capsule a day for 6 weeks then two capsules a day for 6 weeks. Each participant will have blood tests at baseline, then blood tests and evaluation of side effects at 6 weeks and 12 weeks.

Researchers will compare these results in the participants taking each type of selenium (selenomethionine or methylselenocysteine).

Detailed Description

The main aim of this trial is to evaluate which dose and type of selenium (Se), either selenomethionine or methylselenocysteine, achieves optimal selenium status, in order to maximise its potential for cancer prevention without causing health problems from excessive Se intake. The trial will also evaluate how much Se is needed according to Se blood levels before starting Se in the trial, adverse events and recruitment rates.

This trial will recruit 60 participants from Middlemore and Waikato Hospitals with at least one advanced colorectal adenoma removed through the Bowel Screening Programme. Participants will be randomised (1:1) to take either selenomethionine or methylselenocysteine, dosed at Se 50 mcg/day for 6 weeks then 100 mcg/day for 6 weeks.

Co-primary objectives:

To determine whether:

1. Se 50 µg/day for 6 weeks significantly increases plasma selenoprotein P (SEPP) from baseline;

2. the increase in plasma SEPP from baseline is greater with Se 100 µg/day than 50 µg/day only when baseline plasma Se is below the median value for the trial population;

3. the increase in plasma SEPP from baseline is not different between MSC and SLM at each dose level.

Secondary objectives:

To determine:

1. change in plasma Se levels by Se type and dose;

2. change in white blood cell DNA damage from baseline by Se type and dose;

3. feasibility (assessed by recruitment rates, adverse events, compliance with trial medication and participant experience).

Trial assessments:

* blood tests at baseline, then 6 weeks and 12 weeks after initiating Se dosing;

* adverse events and trial medication compliance assessed 6 weeks and 12 weeks after initiating Se dosing;

* participant experience survey on completion of trial medication dosing.

Study Timeline

• Study First Submitted: 2021-06-14
• Study First Submitted QC: 2021-06-27
• Study First Posted: 2021-07-07
• Study Start: 2022-05-06
• Primary Completion: 2023-12-11
• Study Completion: 2023-12-11
• Status Verified: 2025-01
• Last Update Submitted: 2025-01-19
• Last Update Posted: 2025-01-22

Recruitment & Eligibility

• Status: COMPLETED
• Sex: All
• Target Recruitment: 56

Inclusion Criteria

Participants will have all of the following:

• pathologically-confirmed advanced adenoma (defined as any one of >/= 10mm diameter, >/= 3 adenomas, high-grade dysplasia, tubulovillous or villous adenoma) 5 diagnosed at first colonoscopy in the National bowel screening programme within the previous 6 months;
• no residual colorectal adenomas;
• next colonoscopy planned within 5 years;
• willing and able to comply with all trial requirements, including treatment and assessments;
• signed written, informed consent.

Exclusion Criteria

Participants will have none of the following:

• currently taking selenium supplements (including in multivitamins) or within the last 6 weeks;
• previous history of colorectal adenoma, colorectal cancer or familial colorectal cancer syndrome;
• other significant cancers within the last 5 years;
• concurrent medical conditions that, in the opinion of the investigators, would compromise either participant safety or the integrity of the data (e.g., malabsorption);
• male participants with a female partner of childbearing potential or pregnant, and unwilling to remain abstinent or use effective contraception (including barrier contraception with a pregnant partner).

Study & Design

• Study Type: INTERVENTIONAL
• Study Design: PARALLEL

Arm && Interventions

Group	Intervention	Description
Selenomethionine	Selenomethionine	50 micrograms of selenium as Selenomethionine per oral capsule. Dosage: One capsule a day for 6 weeks, followed by two capsules per day for 6 weeks.
Methylselenocysteine	Methylselenocysteine	50 micrograms of selenium as Methylselenocysteine per oral capsule. Dosage: One capsule a day for 6 weeks, followed by two capsules per day for 6 weeks.

Primary Outcome Measures

Name	Time	Method
Plasma SEPP1 concentration 2	At 6 and 12 weeks	To determine whether the change in plasma SEPP1 from baseline is greater with selenium 100 micrograms/day than 50 micrograms/day only when baseline plasma selenium is below the median value for the trial population.
Plasma SEPP1 concentration 3	At 6 and 12 weeks	To determine whether the change in plasma SEPP1 from baseline is not different between methylselenocysteine and selenomethionine at each dose.
Plasma SEPP1 concentration 1	At 6 weeks	To determine whether 50 micrograms/day of selenium for 6 weeks significantly increases plasma SEPP1 from baseline.

Secondary Outcome Measures

Name	Time	Method
White blood cell DNA damage	At 6 and 12 weeks	To determine change in DNA damage (relative to baseline) by selenium type and dose.
Plasma selenium	At 6 and 12 weeks	To determine change in plasma selenium levels by selenium type and dose.
Treatment-emergent adverse effects	At all time points	To determine the incidence of treatment-emergent adverse effects as classified according to NCI-CTCAE version 5.0
Recruitment	At baseline	To determine to percentage of subjects who after being offered the study continue on to study entry.

Trial Locations

Locations (2)

Counties Manukau DHB; 🇳🇿 Auckland, New Zealand

Waikato DHB; 🇳🇿 Hamilton, Waikato, New Zealand