Radiation Oncology Update- Dr Andrew See
Radiotherapy is typically delivered via a course of painless daily visits on a Monday to Friday basis spanning between three and 6 ½ weeks.
Splitting the treatment up into small sessions delivered daily over many weeks is called ‘fractionation’. Fractionation ensures that the radiotherapy treatment will be safe as the normal body tissues cope very well with radiation when delivered in this manner.
Traditional Fractionation – 6 weeks
Traditionally, radiotherapy has been administered over 6 to 6 ½ weeks comprising between 30 and 33 daily treatments. This is delivered in two phases. The first phase, which spans 5 weeks, is termed ‘whole breast radiotherapy’. During this phase, the whole breast is treated through a technique called opposed tangents. The second phase of treatment, also called the ‘boost’, is delivered in the final 1 to 1.5 weeks. During this component of therapy, just the immediate breast tissue surrounding the original primary tumour is irradiated. Not all women require a ‘boost’ dose however in those who do, it is considered to further improve local tumour control.
Shortening the Radiotherapy Course - 3 weeks
Over the last two decades, a number of clinical trials have explored the merits as to whether it is possible to shorten the duration of whole breast radiotherapy from the traditional 6 ½ weeks to anywhere between three and 3.5 weeks. These studies were conducted in countries where radiotherapy machines were scarce and as a result the waiting times for treatment unacceptably long. Three trials, accruing over 5000 women have now been published and peer reviewed. They appear to show that a select group of women can be safely treated with a shortened 3.5 week course of therapy yet still enjoy equivalent long term cure rates and acceptable cosmetic outcome.
In some groups of women, it is still preferential to extend the treatment over 6 ½ weeks. This is particularly so for women who are large breasted, as the very same trials did show that shortening the treatment in large breasted women can lead to an increase in the risk of long term breast fibrosis and shrinkage, which may lead to dissatisfaction with the overall cosmetic outcome. Furthermore, women who are intending to undergo breast reconstruction of any type and women who also require treatment of the supraclavicular fossa (glands above the collarbone as well as the breast) will generally be managed on a standard six week course.
New Radiotherapy Techniques - Improving Safety and Minimising Risk
In the modern era, radiotherapy is considered safe and equitable although there still are some potential long-term side effects that can manifest years after the treatment has been administered. In the case of women who require left-sided breast radiotherapy one of the long-term side effects involves the potential for radiotherapy to damage the heart. This occurs because the radiotherapy beams do come close to the front of the left ventricle (main chamber of the heart that pumps blood around the body) and also the left anterior descending coronary artery (main artery that feeds the left chamber of heart). Although the overall risk is considered to be low, a small increase in ischemic heart disease is observed when treating left sided breast cancer that is not apparent when managing right sided disease. This risk is magnified even further in women requiring left sided breast radiotherapy who also have other cardiac risk factors such as diabetes, active smokers, hypertension or a familial history or predisposition for heart disease.
Deep Inspiratory Breath Hold For Left Sided Breast Cancer
A recent refinement in the management of left-sided breast cancer is a technique called ‘deep respiratory breath hold’ or DIBH.
A single treatment of radiotherapy usually lasts 6-10 minutes. During this time women are asked to take shallow comfortable breaths in and out of an open mouth.
With deep respiratory breath hold, additional coaching occurs prior to radiotherapy planning and women are asked to take a deep purposeful breath inward and then to hold the inspired position for as long as they feel comfortable (20-30seconds). The radiotherapy is only administered while the breath is held in this phase. This manoeuvre pushes the heart back and away from the radiation beam further reducing the dose to the heart. Women are usually required to wear video feedback goggles or watch a computer monitored during their therapy which allows instant feedback as to whether their breathing is maintained in the desired phase. Furthermore, breathing drills similar to which are taught in a Yoga class are practiced in the weeks leading up to the commencement of radiation therapy. Not all radiotherapy departments offer this technique although in the years ahead it is likely to be more widely available.
Dr Andrew See consults out of the unit on Monday mornings.
Melbourne Breast Unit
29 Simpson St,
East Melbourne VIC 3002
Phone: 03 9419 1166
Fax: 03 9419 6416