Breast Cancer

Breast Cancer

There is much to say about breast cancer. Being one of the most common cancers in the world, there are quite literally, whole books on the subject making it difficult to write about in a few paragraphs. Having said that, let us focus on radiotherapy treatments. Right from the start there is a fundamental difference in treating the breast cancer. It is an organ on the upper thorax, external to the rib cage. This poses a set of questions and there is still a debate on what the best treatment approach is.

Traditionally, breast radiotherapy treatments were done using 3D conformal technique (3DCRT) through glancing fields encompassing the breast. The use of such beams allows the treatment to be done without irradiating the opposing breast and lung but with an excess dose to the axilla. This technique uses bi dimensional beams with collimators giving it the breast shape. Confused? Let’s try and shed some light over the subject for those of you that are not from the radiotherapy area. Think of a flashlight. When you turn the light on and project it onto a wall you will have a bi dimensional light field, which is the same to say that it has a height and a width. In this example, a collimator would be something that you put in front of the light, blocking a part of it, and leaving a “shaped” beam to pass through.

This has been the main technique used to treat breast. With the introduction of intensity modulated radiation therapy (IMRT) techniques, it has lost a bit of ground but still is widely used. IMRT allows the use of three-dimensional beams that consider, not only the height and width, but also depth. So, what exactly is the difference? Continuing to use our flashlight analogy, imagine that the object placed in front of the light acts as a filter allowing different light intensities to pass through within the light field. In this example we would have a light field with different focus points where there are more luminous parts than others.

What does that mean for the treatment itself? In practical terms this means that, potentially, IMRT techniques allow for bigger and sharper dose gradients, resulting in a better ability to concentrate the higher doses to the treatment volume, hence, better lung and heart sparing.

Does that mean the IMRT techniques are better for breast cancer treatments? Before we answer that question, there is a little more to say about the IMRT techniques. The standard form of this technique is an extension of 3DCRT where the intensity of field is modulated in fixed beam incidences. A more recent approach is one where the modulation is done in a rotational beam. This one is also called volume modulated arc therapy (VMAT).

Also, before addressing the question, there are other things to consider, namely, the availability or use of auxiliary techniques such as image guided radiation therapy (IGRT), deep inspiration breath hold (DIBH) and gating. Covering all of these in detail would make this article too long for a blog entry but they are covered in the Glossary and could be a good topic for a future blog. Although these are not treatment techniques in themselves, they allow for more precision during the treatment. 

So, which exactly is better? Just like most of things in life, better is decided by comparing a set of criteria against characteristics in relation to a particular circumstance or case. When choosing the best technique to use for treating a breast cancer, it is a similar situation. We must first say what better is in the particular case. While the IMRT techniques allows for more conformal doses to the target volume it also is more prone to have low doses around the opposite lung and breast. Patients treated with 3DCRT techniques may be able to avoid giving dose to opposite lung and breast but have higher axillary doses.  Also, the availability and use of auxiliary techniques plays a role in choosing the best technique. Some, like IGRT, allows for precise patient positioning while others, like DIBH or gating techniques, allow for better heart sparing. In the end the decision on what to use will always depend on the team assessment of the patient since some of these also need the patient’s active collaboration.

Regardless of the techniques used, the level of experience and training within the team treating with these techniques is critical. An experienced RTT can efficiently train and position the patient while an experienced dosimetrist can take the most advantage of the available techniques to meet the treatment goals.

Ultimately, the decision on what to use will also depend on the resources available. The radiotherapy field is always growing and improving, and the modernization of a department can be a challenging process since there are multiple choices of equipment and vendors. 

If you are planning to implement new techniques or buying new equipment into your department, check out the Mercurius Health solutions to help you along the way. Here’s how.

André Pereira


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