DESTINY-Breast 04 is basically a phase III randomised clinical study for the low HER2 metastatic
breast cancer with one to two prior chemotherapy exposures. It’s a comparison between trastuzumab
deruxtecan, T-DXd, with treatment of physician’s choice. The original data with the efficacy and
adverse events was presented at ASCO 2022 by Dr Modi at Memorial Sloan Kettering and it had a
phenomenally great outcome for progression free survival, including the secondary overall survival
there was a statistical difference and we understand the overall adverse events.
So the study that I presented was based on this efficacy improvement outcome. We had additional
patient-reported outcomes to be studied formally for the hormone receptor positive population. The
patient-reported outcome was done by a pre-validated survey and this included cancer specific,
breast cancer specific and general. The main thing is to really understand the global health status
which is a reflection of the quality of life. So those are the things that we measured but we also had
additional fatigue and nausea and pain reviewed.

What did you find?

What we found is that the global health status was well maintained, it did not deteriorate by the use of
T-DXd. Similar in the TPC side also we found the same thing. Fatigue was also well maintained with
no major deterioration. The nausea and vomiting, the early cycles there was some deterioration in
cycle 3 and cycle 5 but during the course of the 27 cycles what we noticed is that there is a reduction
of the nausea, it did not further deteriorate.

When you actually look into the time to deterioration there is a significant prolonged improvement on
the T-DXd side compared to regular chemotherapy. Particularly for symptoms like pain there is a fairly
significant long-term pain control and this resulted in a hazard ratio of 0.4.

What impact could these findings have?

This impact is really to understand the patients’ perspective. We know that efficacy and adverse
events on T-DXd is reasonable but that doesn’t always mean that the patients will be feeling that way.
This is a balance between efficacy and safety of the patients’ perspective. We’ve confirmed now from
the patients’ perspective that this is really not just effective but patients’ overall quality of life does
improve by this treatment. Considering metastatic breast cancer, improving the quality of life is
extremely difficult so this is fairly impressive data that we obtained from this study.