The main outcome of the study is the regional recurrence-free survival after a median follow-up of five years. And what we see is that regional recurrence-free survival is 96.6% for the central lymph node biopsy arm and 94.2% for the non-central lymph node biopsy arm. And that is corresponding to an absolute difference of 2.35%. And there is something statistically important, but rather complicated...
The main outcome of the study is the regional recurrence-free survival after a median follow-up of five years. And what we see is that regional recurrence-free survival is 96.6% for the central lymph node biopsy arm and 94.2% for the non-central lymph node biopsy arm. And that is corresponding to an absolute difference of 2.35%. And there is something statistically important, but rather complicated. And it’s about the confidence interval. And the confidence interval, which is really important here, is below 5%. And that is what we said before, it should be below 5%. And that means there’s no statistical difference between these two treatment arms. And that’s the most important outcome. And if you have a look at regional recurrence, we see eight regional recurrences in the central lymph node biopsy arm and three regional recurrences in the non-central lymph node arm and three in the central lymph node biopsy arm. And we know that these event rates are just really low. Yeah, we know central lymph node biopsy is related to shoulder complaints, to arm complaints, neurologic things, lymphedema. We didn’t check that perfectly. What we do know is the impact on quality of life. And published that already and what we see is significant impact of the central lymph node on health-related quality of life and on breast and arm symptoms. We’re gonna check that by five years again so we’ll come back with that next year. I think what we did is we did a whole study and at the end we had this whole patient group and we checked which is the biggest sub-analysis population and that seemed exactly in line with the advice of the SOUND and NSEMA study. So the SOUND and NSEMA study both advised to omit the central lymph node biopsy in T1 grade 1-2, a hormonal receptor positive breast cancer in patients above the age of 50. So we took this patient population out of the whole group of the BOOG 308 study and we checked events like local recurrence, regional recurrence, contralateral breast cancer, death events. And we checked them for the BOOG 308 study, the subpopulation, but we also checked it for the SOUND and NSEMA. And what you can see is that event rates and event percentages are quite similar among studies. So what we say is what SOUND and NSEMA said already, is you can omit the central lymph node biopsy in that specific subgroup, which is like a really low risk subgroup. It’s a low risk subgroup, but it’s quite a substantial subgroup of the whole breast cancer population. The knowledge we add is that in comparison to the SOUND and its tema, Dutch medical oncologists didn’t give 100% endocrine therapy. The amount of endocrine therapy is so impressively lower compared to other studies. And still we have this really good event rates, this really low event rates. So earlier, I think a lot of people thought that endocrine therapy would be a prerequisite for omission of the central lymph node biopsy. And we say it’s not. So not giving endocrine therapy is okay in this low risk population. And there is something else I want to add. In other studies, you often see radiotherapy upgrading. Radiotherapy of the axillary region, even fields who go up higher. We asked our radiotherapists to stick to the ERDC atlas, and that is what they really did really well. So sticking to protocol was really, really high, and only in 1.5% of the patients, axillary fields were radiated incidentally. That is really, really low and actually that means that the medical oncologist gave systemic therapy to the central lymph node biopsy arm and to the non-central lymph node biopsy arm equally so they didn’t change their strategy in case they didn’t know the central lymph node status and the same accounted for the radiotherapist. So what we see here is that the only thing which really mattered is the central lymph node biopsy by itself.
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