Taking vitamin supplements during breast cancer chemotherapy could raise death risk by 40% and make the cancer more likely to return, study finds

• Antioxidants may prevent the exact process chemotherapy relies on
• Pills including vitamins A, C, E and B12 were found to have negative effects
• Doctors now have evidence to tell patients to avoid supplements, an expert said

Taking vitamin supplements or antioxidants during breast cancer chemotherapy could make the disease up to 40 per cent more likely to come back.

A study found the popular pills also raised the risk of someone dying of the cancer.  

Doctors may already tell patients to avoid taking supplements during chemo, which is a damaging therapy which should be completed as quickly as possible.  

But a study has brought new evidence of the risks they bring, and suggested how the pills interfere with the treatment.

Scientists suggest that antioxidants make chemotherapy less effective because they have the direct opposite effect on the body that chemo drugs do.

Scientists found taking antioxidants such as carotenoids, Coenzyme Q10 and vitamins A, C, and E could raise the risk of breast cancer returning by up to 41 per cent (stock image)

Researchers from the Roswell Park Comprehensive Cancer Center in Buffalo, New York said chemo relies on a process called oxidative stress.

In oxidative stress oxygen molecules in the body change to make them unstable and more destructive to other cells – it happens naturally but can also be triggered by drugs, such as chemotherapy, to target tumour cells in particular.

Whereas antioxidants, which in the study included vitamins A, B12, C and E, as well as iron and omega-3 oil, are intended to prevent oxidative stress taking place.

‘It’s thought that antioxidants might interfere with the ability of chemotherapy to kill cancer cells,’ said Dr Christine Ambrosone, the leader of the study.

Breast cancer is one of the most common cancers in the world. Each year in the UK there are more than 55,000 new cases, and the disease claims the lives of 11,500 women. In the US, it strikes 266,000 each year and kills 40,000.

Breast cancer develops from a cancerous cell which develops in the lining of a duct or lobule in one of the breasts.

When the breast cancer has spread into surrounding breast tissue it is called an ‘invasive’ breast cancer. Some people are diagnosed with ‘carcinoma in situ’, where no cancer cells have grown beyond the duct or lobule.

Most cases develop in women over the age of 50 but younger women are sometimes affected. Breast cancer can develop in men though this is rare.    

The usual first symptom is a painless lump in the breast, although most breast lumps are not cancerous and are fluid filled cysts, which are benign.

The first place that breast cancer usually spreads to is the lymph nodes in the armpit. If this occurs you will develop a swelling or lump in an armpit.  

Treatment options which may be considered include surgery, chemotherapy, radiotherapy and hormone treatment. Often a combination of two or more of these treatments are used.   

The outlook is best in those who are diagnosed when the cancer is still small, and has not spread. Surgical removal of a tumour in an early stage may then give a good chance of cure.

The routine mammography offered to women between the ages of 50 and 70 mean more breast cancers are being diagnosed and treated at an early stage.

For more information visit breastcancercare.org.uk or www.cancerhelp.org.uk 

‘One way chemotherapy works is by generating lots of oxidative stress.

‘The thinking is that antioxidants may block oxidative stress and make chemotherapy less effective.’

In their study the researchers focused on 1,134 patients who filled out surveys and were tracked for around six years.

Participants were quizzed about their use of supplements and about their lifestyle, diet and exercise habits.  

The researchers found patients who took any antioxidant at the outset and during chemotherapy – including carotenoids, Coenzyme Q10 and vitamins A, C, and E – were 41 per cent more likely to have their breast cancer return.

They were also 40 per cent more likely to die during follow-up compared to patients using no supplements.  

Women taking B12 were found to be 83 per cent more likely to experience a recurrence and 22 per cent more likely to die during follow-up compared to those who did not take those supplements. 

Women taking omega-3 supplements before and during chemo had a 67 per cent higher likelihood of recurrence and those taking iron supplements were 79 per cent more likely to experience a recurrence.

The results dictate relative risk, which means 79 per cent of the women didn’t see their cancer return, only 79 per cent more than the original non-supplement risk.

For example, if the risk of recurrence for all women was one per cent, for women taking the omega-3 supplement it was 1.79 per cent. 

Dr Amy Tiersten, a professor of medicine at Mount Sinai University in New York, was not involved in the study but said she was glad the research had been done.   

‘For years we have been cautioning patients about the use of vitamins, in particular anti-oxidants, during chemotherapy for breast cancer,’ she told Reuters.

‘There has been ongoing theoretical concern about the fact that while antioxidants may protect normal cells from the toxic effects of chemo, we don’t know that they don’t also protect the cancer cells. 

‘Now we have solid data to back up that concern. 

‘I am a bit surprised by the magnitude of the effect, a 41 per cent increase in the risk of recurrence for patients taking these supplements. 

‘I have always told patients on chemotherapy that the best way to get their vitamins is through a well-balanced diet and will continue to do so given these data.’

The research was published in the Journal of Clinical Oncology.

Source: Read Full Article