Melanie Cole, MS (Host): Welcome to UAB MedCast. I'm Melanie Cole. And today, our discussion focuses on partial breast radiation for breast cancer. Joining me is Dr. Hunter Boggs. He's a radiation-oncologist and an Associate Professor of Radiation Oncology at UAB Medicine. Dr. Boggs, it's a pleasure to have you join us today. As we start in this topic, tell us a little bit about partial breast irradiation and how it differs from whole breast radiation. What are we talking about today?

Hunter Boggs, MD: Yeah. Thanks for having me, Melanie. So, we are specifically focusing this discussion on patients with early stage breast cancer treatment. For patients with stage zero or stage I, early stage breast cancer, the typical options for surgery are a lumpectomy or a mastectomy. For patients who have a lumpectomy, radiation treatment after lumpectomy has been shown to reduce local, regional recurrence, and has been a mainstay of treatment for many, many years.

What we found in probably the last 15 years or so is that there's a certain subset of patients with early stage breast cancer who do not need whole breast radiation treatment, and that can just benefit from radiation treatment to the lumpectomy and to the surrounding tissue. And so, that is becoming an increasingly attractive option to patients as well as to providers.

Melanie Cole, MS: Then, let's talk about the current guidelines, Dr. Boggs, for selecting patients who are eligible for this type of breast radiation therapy. Speak about patient selection.

Hunter Boggs, MD: Yeah, sure. So, typically, at UAB, we follow the ASTRO accelerated partial breast guidelines. The update was published in 2023. Suitable patients are patients that are stage 0 DCIS, or stage I with invasive tumors up to two centimeters. They need to have surgically negative margins. Typically, they're estrogen and progesterone positive. They can be 40 years or older. They do not have cancer in their lymph nodes. And they need to have an acceptable lumpectomy cavity size to normal breast ratio. And these are patients that are suitable. There are some cautionary patients such as patients that have invasive lobular carcinoma, or if they have a genetic mutation. These are things that we would discuss with the patient. But we typically follow the suitable criteria for delivering partial breast irradiation.

Melanie Cole, MS: So, how does it compare to whole breast radiation in terms of efficacy, side effects for early stage breast cancer?

Hunter Boggs, MD: Yeah. So, there are multiple different techniques to deliver partial breast irradiation treatment. Most historically, there has been brachytherapy where catheters were delivered into the patient's breasts and delivering radiation twice-a-day. Those techniques had really good outcomes, and we have probably the best long-term data on that. But it is a more invasive procedure and you need to go to a high volume center really in order to have that done Well. We've not done that typically at UAB. There have been multiple studies that have shown that for well-selected patients, that partial breast irradiation treatment is really non-inferior to whole breast.

And so, your chance of cure from breast cancer is the same using more modern techniques. The toxicity actually is improved compared to whole breast radiation, and that's because you're treating less of the breast. So, you're going to have less fibrosis, less erythema, less tenderness, less fatigue, and potentially shortening your overall radiation course.

Melanie Cole, MS: So, the benefits to the patient as far as quality of life, it really is much better, yes?

Hunter Boggs, MD: That's right. Yes. So, benefits to the patient-- they've done quality of life studies on this-- shortened time having to come back and forth for treatments as well as reduced skin and local irritation and fatigue have been shown in studies to be statistically improved when partial breast irradiation treatment is delivered using modern techniques compared to whole breast radiation treatment.

So most patients, when you present this to them and you say that there's really no difference in outcomes, they will choose partial breast irradiation due to reduced side effects and reduced total area of body that has to be radiated.

Melanie Cole, MS: Speak about the most recent research findings, Dr. Boggs, on long-term outcomes. Tell us a little bit about how that's evolved and what we know now for outcomes for the patient.

Hunter Boggs, MD: Yeah. So, there were two large randomized studies that were published several years ago. There was an NSABP study. And then, there was a study called the RAPID Trial. These studies sought to establish non-inferiority of partial breast radiation in well-selected candidates over whole breast radiation.

While the NSABP study did not meet non-inferiority criteria, there was a very small difference in ipsilateral breast tumor recurrence. The overall difference in recurrence in 10 years was less than 1%. And the whole breast arm, the recurrence was 3.9%. In the partial breast arm, it was 4.3%. So, when you're talking with patients, that's clinically very, very little difference. And that study also included patients that have a little bit more advanced disease than what we typically would recommend as suitable for partial breast irradiation treatment.

The RAPID study used a little bit older radiation techniques, something called 3D treatment, where they would kind of come in with different fields at different angles, and it was delivered twice-a-day over a total of five days, so ten treatments. In that study, there was no difference in recurrence, however, there was increase in side effects for the patient. There was more fibrosis and there was more scarring, and there was more reduction in the size of the treated breast. And a lot of that had to do with the fact that these older techniques, these 3D techniques used very large kind of setup margins. You know, if you're not certain where the breast is going to lie every day, if you're not certain where the lumpectomy cavity is, then you have to increase essentially your setup or your safety margins, which is what was done. And so, we've really moved away from some of these older techniques and have also moved away from doing twice-a-day treatment to doing once-a-day treatment, typically over five days.

The current standard of care was set forth in a phase III study by the folks in Florence, in Italy. And it randomized patients to whole breast or daily radiation treatment, so five fractions. Actually it was delivered every other day, but it was over a total of five fractions. And what they found was actually a reduction in toxicity, and that's because they used a technique called IMRT. IMRT is where you come in with multiple different fields at different angles, and you can really carve off some of the low and medium dose spill to the rest of the breast and still preserve the area that you're trying to treat. And so with that, they found that doing once-a-day treatment, that you have the same outcome and you actually have reduced toxicity. So, that's really kind of set the stage for the current standard of care. And that is available at most centers where you go to get radiation treatment.

Melanie Cole, MS: That's a pretty exciting time in your field, Dr. Boggs. And these advancements are really increasing the quality of life. And as you said, recurrence rates, there's not a big difference or is it significantly less?

Hunter Boggs, MD: There's really no difference. So, we're reducing the amount of breasts that's treated, because most of the time when these tumors come back, they come back near the same quadrant as where the tumor was taken out, okay? So, there's really not a difference in recurrence. Most of these patients have very early stage disease anyway. They don't have very high recurrence rates kind of at baseline. These are very good prognosis tumors. And so, meaningful deescalation of treatment is really important when you choose the appropriate patients.

Melanie Cole, MS: So, that segues nicely into contraindications for appropriate patients. Tell us, are there any? Are there reasons why some patients might not be able to get this?

Hunter Boggs, MD: Yeah. So, one big one is if you scan a patient and their seroma after the lumpectomy is too large compared to the rest of their breast, then we're really not able to adequately spare breast tissue. So, that may be a contraindication to partial breast treatment.

There may be patients with lobular disease, I mentioned that before. There's a little bit more of a higher risk of failing elsewhere in the breast, node-positive disease, triple negative. If their lumpectomy cavity is too close to the skin, that also is potentially a contraindication. It actually is a preferred technique if a patient is eligible in someone who's had radiation treatment previously. So, sometimes patients have had whole breast radiation, and they come back in and they've had a recurrence. And if they do not choose to have a mastectomy, in certain situations, we actually can do partial breast irradiation treatment after that, so for a second time, because we're treating a smaller area.

Melanie Cole, MS: Tell us, Dr. Boggs, how do the latest advancements in these imaging technologies enhance the effectiveness of this type of therapy? And what's really exciting in your field right now?

Hunter Boggs, MD: Yeah, absolutely. So, one thing I wanted to spend a little bit of time talking about was a new technology that we have at UAB called adaptive therapy. So typically, a patient comes in for treatment. We scan them, call a simulation to get them ready for radiation. It takes about a week and a half to two weeks to plan out the treatment, and then we are going to deliver the plan based off the anatomy that we saw at time of simulation.

What we have found is that, over time, patient's breasts will change. Their seromas will often reabsorb, they will look different every day. And so, you have to account for that if you're just planning upfront by having larger setup margins. So, what adaptive therapy does is we scan the patient as normal, we plan out their treatment, and when they come back in the first day, we re-scan them. And we see what the lumpectomy cavity looks like that day, right before treatment. And the physicist is there, the physician is there, the therapist, and we redraw the lumpectomy cavity based off of what it looks like that day. And that allows us to kind of shrink into, adapt our treatment down to the patient's anatomy for that day. And because we know exactly how everything is setting up, we actually can be much tighter in our setup margins. So, that allows for a smaller amount of breast tissue to be irradiated. We also have an updated CT that we take right before the patient starts treatment. That allows us to really accurately see the lumpectomy cavity.

So, this is probably one of the most exciting things that we're doing at UAB is, discussing adaptive therapy for these patients. And we have clinical trial right now open about reducing these margins even more. And that's generated a lot of excitement among patients.

Melanie Cole, MS: It certainly has. And Dr. Boggs, as we get ready to wrap up, how do general practitioners play a role in monitoring and supporting their patients following partial breast radiation therapy? And what would you like other providers to know about all the exciting work that you're doing at UAB Medicine?

Hunter Boggs, MD: Yeah, sure. So, I think it's important in the followup setting to, make sure that patients are continuing to do self-breast examinations. They're often their biggest advocate at finding new disease. Often, anywhere from six to twelve months after radiation treatment, there can be some scarring there. And we don't always rush necessarily to go get a biopsy because that can be a little bit of fat necrosis in that area. And so if you kind of over-biopsy something or you take a mammogram too soon after radiation treatment, really anytime before six months, it's really not recommended to try to go back in and re-biopsy to try to let the tissue heal up.

 If the patient's having some symptomatic scarring and fibrosis, you can use pentoxifylline and vitamin E sometimes to reduce some of that scar tissue formation. But I think really just, you know, the mainstay of breast cancer followup is really good physical exams, and then annual imaging with mammograms or MRIs if indicated. So, those are some of the things that are really important to know.

Melanie Cole, MS: Thank you so much, Dr. Boggs, for joining us today and really sharing your expertise on this type of therapy. It's really a game-changer. It's changing the landscape for radiation therapy. So, thank you so much again. And for more information, you can visit our website at uabmedicine.org/physician. That concludes this episode of UAB MedCast. I'm Melanie Cole. Thanks so much for joining us today.