Selenium and vitamin E in bladder cancer: more harm than good

For years, vitamin E and selenium were a beacon of hope for recurrent Non-Muscle-Invasive Bladder Cancer prevention. But current data calls for caution.

The benefits of selenium and vitamin E for the human body

Selenium is an essential trace element that must be externally supplied to the body.
In the human body, the largest proportion of selenium is stored in the skeletal muscles. However, other tissues and all organs are also dependent on it.
Due to its antioxidant effect, selenium is considered an effective cancer protector.
Vitamin E (tocopherol) is one of the fat-soluble vitamins and comprises a whole range of substances. It is mainly absorbed from plants and stored in fatty tissue.
As an antioxidant, vitamin E also protects against cell damage and can therefore prevent malignant changes.

Why take dietary supplements for bladder cancer?

The prognosis for bladder cancer is still poor. Many tumours in the early stages progress despite treatment or recur after resection. They recur in up to 80% of patients and develop into muscle-invasive bladder cancer in up to 45% of patients.

The need for effective chemoprevention is therefore crucial. A research team from England investigated whether selenium and vitamin E are really suitable for this purpose in a multi-centre, double-blind, placebo-controlled study (DOI: 10.1001/jamanetworkopen.2023.37494). They recruited 270 patients with newly diagnosed NMIBC from 10 UK hospitals. After transurethral resection, they were randomised into four groups:

Selenium (oral: 200 μg/d selenium-rich yeast, 364% of the recommended daily dose) plus vitamin E placebo.
Vitamin E (200 IU/d d-alfa-tocopherol, 600% of the recommended daily dose) plus selenium placebo.
Selenium plus vitamin E.
Placebo plus placebo.

The median duration of treatment was 1.5 years and the follow-up period was 5.5 years. Most patients took the preparations reliably, which was determined on the basis of returned tablets or capsules and diary entries.

Can selenium or vitamin D improve the prognosis of bladder cancer?

The researchers were primarily interested in the recurrence-free interval (RFI). This was the first disappointment: of the total of 122 recurrences, 60 (49%) occurred in the selenium arm and 62 (51%) in the placebo arm, although the difference was not significant. Although the results for vitamin E were significant, they did not show a prolongation, but rather a shortening of recurrence-free survival.

The secondary endpoints of progression-free interval (PFI), overall survival and quality of life did not look much better. Although the supplements were not a disadvantage here, they did not bring any improvement either.

This confirms what has been repeatedly observed in more recent clinical studies with selenium and/or vitamin E in primary and secondary cancer prevention: that they have either no effect or even a harmful effect. Nevertheless, the researchers emphasise that studies on dietary supplements in cancer prevention remain important.

Conclusion for medical practice

Patients with NMIBC do not benefit from selenium or vitamin E supplementation in terms of recurrence, progression or overall survival. Additional vitamin E supplementation may even be harmful. This is yet another reminder that even over-the-counter preparations should not be taken uncritically, but only if there is a manifest deficiency or increased need.

Source

Bryan RT et al. Selenium and Vitamin E for Prevention of Non–Muscle-Invasive Bladder Cancer Recurrence and Progression: A Randomized Clinical Trial. JAMA Netw Open. 2023; 6(10): e2337494. doi:10.1001/jamanetworkopen.2023.37494