Expert Reviews IDEA, TARGIT-B, and NeoORB Breast Radiation Data From ASTRO 2026

CancerNetwork® spoke with Leah Katz, MD, MPH, vice chair of Faculty Development and an attending radiation oncologist in the Department of Radiation Oncology at the University of Miami Miller School of Medicine, about the abstracts featured in the breast cancer Science Highlights session at the 2026 American Society for Radiation Oncology (ASTRO) Annual Meeting, for which she served as discussant. The session included 10-year outcomes from a phase 3 randomized trial of hypofractionated vs conventional fractionated postmastectomy radiotherapy (NCT00793962),¹ long-term follow-up from the IDEA trial (NCT02400190) of endocrine therapy without radiotherapy,² initial outcomes from the randomized TARGIT-B trial (NCT01792726) of an intraoperative tumor bed boost,³ and interim findings from the phase 3 NeoORB trial (CTRI/2024/06/068847) of neoadjuvant radiotherapy.⁴

Katz discussed which findings are most likely to change practice right away, the caveats around omitting radiation for patients with favorable-risk disease, what the TARGIT-B and NeoORB data suggest about how radiation interacts with an intact tumor, and why she believes the field is moving away from asking whether to give radiation and toward asking who should receive it and when.

CancerNetwork: There are multiple abstracts being discussed in the session you’re on the panel for. Which do you think will have the most immediate practice impact?

Katz: Very practically, I would say the most immediate impact will be from hypofractionation vs conventional fractionation in postmastectomy patients.¹ This is a practice that is already in place, but not everybody does it because there’s still limited data. This is longer-term follow-up showing that there’s safety and good efficacy with it. I would say it will make more people comfortable using it, beyond those who are already using it. The other studies are extremely interesting and potentially practice changing. However, some of them require validation and will take longer to adopt.

Dr Jagsi’s data look at omitting radiation entirely in biologically favorable postmenopausal patients.² Where is the field on de-escalation like this?

Katz: That’s a great question, and I do mention this in my talk. In very carefully selected, well-informed patients, it is a great option. However, there are 2 caveats that get lost in the conversation around this. The first is that endocrine therapy is very hard for women to tolerate. Omitting radiation relies on women taking a daily pill for 5 years, and to be honest, some people have intolerable [adverse] effects. Once we know that a person is going to have intolerable [adverse] effects, the window for radiation efficacy has already closed. A lot of women say to me, “Can I try the pill, and if not, I’ll do the radiation?” It doesn’t work like that.

The other thing I’d say is that whole breast radiation can now be delivered very safely over 1 week. The prior narrative of radiation being very cumbersome, difficult, and painful is no longer the case. Our techniques have gotten so good, and our fractionation schedules have gotten so short.

That’s a long-winded way of saying it’s a great option for women who are carefully selected and don’t need radiation. However, it doesn’t necessarily speak to the fact that radiation still offers an incremental benefit in risk reduction, even when it is safe and tolerable, from a local risk threshold, to omit it. Radiation still offers a benefit, and we see that in the older data, which show that in a very selected, low-risk population, radiation plus endocrine therapy still brought local recurrence down. It’s a great study, and I’m glad we have it. However, we need to take these other things into account.

The TARGIT-B trial tests an intraoperative tumor bed boost for young or higher-risk patients.³ How does that change the sequencing conversation with surgery?

Katz: The TARGIT-B study showed equivalent local recurrence with an intraoperative radiotherapy boost vs an external beam boost, so we know that it’s safe. The more interesting conversation about the TARGIT-B study, which I address in my talk, is that it also decreased distant metastatic recurrence. We know that a local recurrence increases your distant metastatic rate, for reasons that are not scientifically clarified yet but are going to be very interesting for us to elucidate. The boost blunted that effect, which is incredibly interesting. What will happen in the future, after more studies and more stratification are done, is that there’s going to be a biologically advantageous group to offer the TARGIT boost to.

The NeoORB study looked at the optimal sequencing of neoadjuvant radiation.⁴ Why does sequencing matter so much here?

Katz: It’s the same story, in that neoadjuvant radiation offered a greater tumor volume reduction than systemic therapy alone. It was a little bit of a similar story to TARGIT-B, in that it also reduced nodal recurrence. It raises the question: Is something happening at the interface of radiation and an intact tumor that allows for lower recurrence down the line? That’s quite interesting.

As I say in my summary slides, we may be thinking too narrowly about the conventional breast surgery and radiation framework, which is surgery with negative margins, then radiation to kill microscopic disease. Radiation may offer all sorts of treatment paradigms and opportunities if we deliver it at a different time, at a different moment during the breast tumor, meaning in the breast vs out of the breast.

Looking at these studies, is there a theme connecting them that you’ll highlight in your discussion?

Katz: The theme I’m highlighting is that it’s about patient selection. While the IDEA study does look at omission, instead of us always trying to give less radiation, we’re going to turn the field toward who and when vs yes or no in terms of radiation, because it continues to show efficacy.

Finally, what’s still missing from these data that you’d like to see studied next in breast radiation oncology?

Katz: Radiation alone in the subset that the IDEA study looked at, in terms of local recurrence and other outcomes. That’s interesting; I haven’t really thought about what is missing. There’s so much data there, but what’s missing is just a lot of validation of this and whether it’s going to be practice changing.

References

1. Sun GY, Chen SY, Yu T, et al. Hypofractionated vs conventional fractionated postmastectomy radiotherapy in high-risk breast cancer: 10-year outcomes from a phase 3 randomized trial. Presented at: 2026 ASTRO Annual Meeting; September 26-30, 2026; Boston, MA. Abstract 1.

2. Jagsi R, Griffith K, Harris EER, et al. Long-term follow-up of a prospective multicenter trial of endocrine therapy without radiotherapy after breast-conserving surgery for biologically favorable stage I breast cancers in younger postmenopausal patients. Presented at: 2026 ASTRO Annual Meeting; September 26-30, 2026; Boston, MA. Abstract 354.

3. Vaidya JS, Bulsara MK, Tobias JS, et al. Initial outcome of the TARGIT-B international randomised trial of targeted intraoperative radiotherapy tumour bed boost for young or high-risk patients with breast cancer. Presented at: 2026 ASTRO Annual Meeting; September 26-30, 2026; Boston, MA. Abstract 349.

4. Nair RP, Pareek P, Devnani B, et al. Neoadjuvant radiotherapy in breast cancer: a study on the optimal sequencing of radiation in breast cancer (NeoORB). Presented at: 2026 ASTRO Annual Meeting; September 26-30, 2026; Boston, MA. Abstract LBA 09.

5. Song Y, Zhai Y, Lan B, et al. Phase I/II study of concurrent abemaciclib and adjuvant radiotherapy in patients with HR+, HER2-, high-risk breast cancer. Presented at: 2026 ASTRO Annual Meeting; September 26-30, 2026; Boston, MA. Abstract 321.