Updated Breast Cancer Guidelines Help Evolve Radiation Decisions

Laura M. Freedman, MD

The use of post-mastectomy radiation has historically been a controversial topic in patients with 1 to 3 positive lymph nodes, according to Laura M. Freedman, MD. Revisions to the National Comprehensive Cancer Network (NCCN) guidelines have, however, have now allowed physicians to pinpoint the women who are most likely to benefit from the treatment.

Additionally, American Society for Radiation Oncology guidelines for accelerated partial irradiation have been revised to include younger patients with ductal carcinoma in situ (DCIS). Although these recommendations now encompass a greater percentage of patients with breast cancer, technological advances in CT scan-guided treatment have helped physicians target radiation doses.

“Treatment planning techniques, like proton and intensity-modulated radiation, allow for much better dose conformity,” says Freedman.

OncLive®: Can you discuss the state of radiation oncology in breast cancer, which you focused on in your presentation?

In an interview during the 2018 OncLive^® State of the Science Summit™ on Breast Cancer, Freedman, assistant professor, director of radiation oncology, Sylvester Comprehensive Cancer Center, University of Miami Health System, discussed the impact of the updated NCCN guidelines on clinical applications of radiation therapy in patients with breast cancer.Freedman: There are many updates in radiation oncology that came from the 2017 San Antonio Breast Cancer Symposium. First, I wanted all from the medical, surgical, and radiation oncology communities to be aware of the updated guidelines for post-mastectomy radiation given in women who have pathologic T1/T2 tumors and 1 to 3 positive nodes. The guidelines have allowed us to assess the risk-benefit ratio and guide our patients in the decision-making process.

The next topic [of my presentation] was the update to the accelerated partial breast irradiation guidelines. We now have the opportunity to extend partial breast irradiation to more patients in light of new information about intraoperative accelerated partial breast irradiation. The technological advances we have seen in radiation oncology have made it easier for us to provide better outcomes for patients. When the toxicity is lower, the benefit ratio is higher. In that circumstance, we’re able to better treat patients and provide them with the most optimal outcomes.

Why has post-mastectomy radiation been controversial in the past?

Finally, I spoke about the re-irradiation guidelines that are helping physicians extend patients’ lives and provide cures. These options extend to patients who recur as well.It’s very well known that patients with no lymph nodes involved do not derive a benefit from post-mastectomy radiation, although there are exceptions, such as high-risk patients and those with positive margins and early-stage tumors. Typically, they do not show additional benefit post- mastectomy. For patients with 4 or more positive nodes, the addition of radiation provides a positive benefit in terms of local recurrence and overall survival. The data on patients with 1 to 3 positive lymph nodes have been more difficult to obtain.

How have the guidelines affected the use of accelerated partial breast irradiation?

What are some of the technological advances that have helped further treatment?

Do these advances coincide with reirradiation, as well?

How will the role of radiation therapy evolve or change in the next couple of years?

The NCCN guidelines will help streamline the use of radiation in what tends to be a more heterogeneous group of patients. For example, you could have a patient with 1 lymph node involved, 3 mm of disease, and 15 removed lymph nodes or a patient with 3 lymph nodes involved, 2.5 cm of disease, and 5 removed lymph nodes. The risk-benefit ratio in those 2 patients is likely to be very different. This provides a guide for physicians as to which patients are most likely to benefit from the addition of radiation.When the guidelines were first published, they were very conservative. Accelerated partial breast irradiation was only offered to older women with very small tumors and wide margins. The guidelines are much more relaxed now; the age has been lowered, and we have opened it to patients with DCIS. This may be particularly helpful in certain parts of the country where access to radiation might be challenging. Having the opportunity to complete a course of treatment in 1 week, as opposed to 4 to 6 weeks, can be a great option. These guidelines are allowing more patients to be included in the optimal groups to proceed with accelerated partial breast irradiation.For years, we based treatment on plain x-rays and fluoroscopic machines that were very basic and 2-dimensional. As time went on, we moved to CT scan-guided treatment planning. Now, all patients are treated with a CT scan and we have more visibility. We can now see, instead of guessing where the organs are and what the dose homogeneity is in the area. Since the advent of CT-guided treatment planning, we have moved to technology where we can calculate, based on a patient’s breath intake, which areas are likely to benefit from a decreased dose of treatment. This minimizes the dose to nearby normal structures, thereby decreasing toxicity and improving the therapeutic ratio.The ability to use very specific treatment planning to avoid critical structures does potentially allow us to reirradiate an area that might be near a critical structure, like the heart or the lungs. It may not necessarily be used, but the technology nonetheless allows us to provide a more targeted dose.We are going to see much more of a use with protons; this will help spare the nearby normal structures, like the heart and lungs. We may also see greater use of intensity-modulated radiation therapy in an effort to provide a more homogeneous dose and minimize the dose to the heart and lungs.

What challenges is the community still facing?

We’re also going to see a lot more in terms of accelerated partial breast irradiation, because it is a complete course of treatment with a high curative rate. In this course of treatment, the dose is very focused on the tumor bed; that is the No. 1 spot where cancers are likely to recur. By providing a more focused and highly concentrated dose to the area over a shorter span of time, a lot of women will be able to cut down on the time spent away from their jobs and families.One of the challenges that we see is cost. We always have to take into account the cost, the therapeutic-benefit ratio, and the cost ratio; it’s really a scale. Intensity-modulated radiation, particularly the protons, are extremely expensive. Insurance companies don’t necessarily want to pay for this improvement. We may see that the outcomes from the treatment are identical. We will also see an improvement in the toxicity, which will result in less side effects and overall patient improvement. That’s another important factor to consider, but it’s a challenge when we weigh these risks against the costs.