Today we're going to talk about radiation after a mastectomy. Many of you may have been told by your surgeon that you don't need radiation after a mastectomy. The reason we were told that is that most of the time that is true. If you have a mastectomy, and the margins are clear, there's no lymph nodes involved and the tumor is relatively small, there is no indication for radiation after mastectomy.
But there are some features of your tumor that may make you at a higher risk of having a recurrence on the chest wall or in the lymph nodes after a mastectomy, and that your doctor may be sending you to see a radiation oncologist to talk about radiation. So let's go through those risk factors that are indicated for post mastectomy radiation.
The first one is lymph nodes involved with tumor. If you have cancer that has spread to the lymph nodes, your doctor may send you to see a radiation oncologist. Now, if you have between one and three positive lymph nodes involved with cancer, it's not a slam dunk that you'll receive radiation. But it's definitely something where you need to have a conversation with the radiation oncologist to understand the benefits and the risks associated with radiation, because even in that setting with only one to three positive lymph nodes, there are benefits to the radiation. But it just depends on the more nuanced information about the rest of your tumor.
If you're young, if there's spread into the little lymphatic channels, if your tumor is high grade, if it's a triple negative tumor; those are some things that are going to push to recommending radiation even if you have one to three positive lymph nodes. Some doctors just recommend radiation for anyone with positive lymph nodes. But I would say one to three nodes is kind of this gray area. When you have four more positive nodes, it is not a question. Radiation is recommended after the mastectomy. That's the first one: positive lymph nodes is an indication for meeting radiation after a mastectomy.
The second indication is positive margins. So this makes sense. If your doctor took out the tumor in the breast and there are tumor cells extending up to the edge of what he or she took out, there's likely tumor cells left behind on the chest wall. Now, radiation is used to sterilize those cells. So radiation is often recommended after mastectomy if the margins are positive.
The third indication is tumor size. Large tumor size is a predictor for a higher risk of recurrence. This one is a little bit more of a gray zone, but typically tumors larger than five centimeters have a higher risk of recurrence, and radiation should be at least discussed. So it may be in the end that your doctor decides not to give radiation in this setting, but that is another indication.
So, the three indications for post mastectomy radiation for invasive breast cancer are positive lymph nodes, positive margins, and large tumor size (large being defined as greater than five centimeters). Now for DCIS there are also indications for post mastectomy radiation, but it's usually positive margins. And even then, there's some debate about whether or not it's a benefit. So even with positive margins, we're not sure now, and really debating whether or not to use radiation. So I would say with DCIS it's definitely a conversation that you'll have with your surgeon and your radiation oncologist. Those are the reasons that you would need post mastectomy radiation.