Thursday, 2 February 2012

Using time of day to reduce heart damage in breast cancer treatment

A new paper this month suggests that treating breast cancer patients with radiation outside of the hours of 6am to noon will reduce side effects that could damage their heart [1].

Radiotherapy treatment has already been improving rapidly in many ways, to ensure that the tumour recieves the correct dose of treatment, whilst sparing the normal healthy tissue. However, radiation still carries an immediate and a long term risk of damage to the heart. Dr Gupta and his colleagues at the Department of Radiation Oncology in the Tata Memorial Cancer Centre in India, suggest that the correct timing of radiation treatment could minimise these risks further.

Radiotherapy is a common treatment for breast cancer, however one side effect is heart damage (C) CANCERactive 2012
With the significant improval in survival rates of breast cancer patients it has become even more important to minimise any long term effects of radiotherapy. Currently, in England and Wales, more than 70% of women diagnosed with breast cancer will live for at least 10 years, and it is predicted that 64% will live for at least 20 years [2]. Critical coronary artery disease can occur 10-15 years after radiotherapy and so it is vital that these long term effects are analysed.

Oxygen demand in the heart muscle is higher in the morning (6am and noon) but the supply of oxygen is lower. Unsuprisingly, this corresponds to when most heart attacks occur and when the heart is most prone to injury. Many other biological functions are occurring at this time of day that puts the heart at risk to damage: blood pressure is rising, adrenaline and other neurotransmitters are increasing, and people are becoming more active, putting more demand on the heart.

Dr Gupta suggests by avoiding radiation therapy in the morning in breast cancer patients, especially those receiving treatment in the left side, they will avoid short term and long term damage to the heart.

However, most radiotherapy treatment is now precisely targeted to the breast tissue (some radiotherapy machines can be precise to sub-millimeter), and there is speculation as to whether the surrounding heart tissue is effected [3]. It should be highlighted that to date there has been no analysis of the incidence of heart problems in breast cancer patients with standardised timing of radiotherapy, and therefore this is currently still a hypothesis.

Robust trials are certainly needed to address this issue, but the hope is that by using circadian timing, the side of effects of cancer treatments can be minimised whilst still allowing the treatment to be effective in removing the cancer.

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Please note, I'm not a medical doctor, if you have breast cancer then you can speak to your doctor about timing your treatment. The above article is talking about a medical hypothesis (an idea) that has yet to be tested. Many cancer patients also have a desynchronised body clock, which can make it hard to pinpoint the perfect time of day to give treatment, and different treatments might have different times of day when they are more effective/less harmful. I hope you find my blog posts helpful in explaining the latest research and research ideas. Feel free to add a comment and I will try and answer any of your questions.
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[1] Gupta D et al. Cardioprotective radiotherapy: The circadian way. Med Hypotheses (2012), doi:10.1016/j.mehy.2011.12.009

[2] Cancer Research UK website, CancerHelp UK, Breast Cancer Statistics and Outlook, accessed on 28-1-2012

[3] Breastcancer.org Response to "Radiation for breast cancer ups heart disease risk", accessed on 28-1-2012

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