Laura is awarded with recognition from the BOOG Young Investigator Award. She performed her PhD in the lab of Oncode Investigator Jacco van Rheenen’s lab (NKI), taking part in Oncode Institute’s Patient Perspective Program. Based on her work, and with support by Oncode Insitute, a pioneering clinical study is launched that could lead to a simple yet powerful change in how we treat triple-negative breast cancer.

Oncode Institute: Could you briefly explain your discovery about how the menstrual cycle might affect chemotherapy?

Laura Bornes: During my PhD and postdoc, we started looking at how the estrous cycle in mice—which is comparable to the human menstrual cycle—might influence tumors. We already knew that the healthy mammary gland changes throughout the cycle, so we wondered: do tumors change too?

What we found was striking. Tumors in mice looked and behaved differently depending on the cycle stage. We saw changes in how fast the tumor cells were dividing, and differences in the types of immune cells present. Since chemotherapy targets dividing cells, we asked: could these cycle-driven changes affect how well treatment works?

So we gave chemotherapy to mice at different points in the cycle and saw that treatment was more effective during certain phases. We also looked at a small group of breast cancer patients and noticed a similar pattern. That early data helped us design a new clinical trial—now supported by Oncode Institute—to test this idea more thoroughly.

Oncode Institute: Tell us more about the clinical trial. What are you hoping to learn?

Laura Bornes: Our goal is to see if the timing of chemotherapy relative to the menstrual cycle really affects how well the treatment works. We started with existing data from the Netherlands Cancer Institute and LUMC, where we had leftover blood samples and treatment results. But those samples weren’t always taken at the exact time of chemo, and additional information about the menstrual cycle was often missing.

In the new trial called ChemoSense, which is led by Sabine Linn, we’re doing it differently. We’ll collect blood right when patients receive chemotherapy, and we’re asking detailed questions about their menstrual history. We’re focusing on women with triple-negative breast cancer, which helps keep the study group more consistent. The trial is running in five hospitals across the Netherlands, so we can recruit faster and gather more robust data.

If all goes well, we hope to have results in about two years.

Oncode Institute: Where does the trial stand now?

Laura Bornes: Most of the ethical and hospital approvals are in place. At NKI, for example, we already use a “consent at the door” system where patients agree to donate leftover samples for research. But since our trial involves extra steps—like taking new blood samples and tracking the cycle—we needed separate approvals. Those are now complete, and patient recruitment is starting.

Oncode Institute: You mentioned chemotherapy is more effective at certain times in the cycle. Why is that?

Laura Bornes: We do not know exactly but our mouse experiments gave us some clues. In our mouse experiments, we observed that chemotherapy works best on cells that are dividing. In one cycle phase, we saw more tumor cell division—that’s when chemo had the strongest effect.

In the other phase, tumor cells were dividing less, and other factors kicked in: the blood vessels were tighter, drug penetration was lower, and we saw changes in the immune response that are linked to resistance. One surprising finding was that more immune cells—especially macrophages—were present in the less responsive phase. When we removed those macrophages in mice, chemotherapy worked better again. So we think they play a key role, though we’re still figuring out how.

Oncode Institute: What is the future outlook for this research?

Laura Bornes: Our data is mainly based on mouse experiments. With the clinical study, we will be able to investigate the link between the menstrual cycle and chemotherapy responses in the human setting. If there is a link, we hope to get information how to use this knowledge in favor for the patient, something that we currently cannot do yet.

Oncode Institute: You recently received the BOOG Young Investigator Award. What did that recognition mean to you?

Laura Bornes: It was an incredible honor—and honestly, a surprise! My mentor had nominated me, but I didn’t expect to win. This project has been years in the making, from the first experiments to long journal revisions. Getting this recognition made all that effort feel worthwhile.

This all started with a basic, somewhat unusual question. At first, not everyone saw the potential. But now, clinicians and scientists are engaging with it, and that’s really exciting.

Oncode Institute: Speaking of clinicians, how has that collaboration helped shape your research?

Laura Bornes: It’s been essential. We initially reached out to Sabine Linn, and later connected with Marleen Kok and others at Leiden University Medical Center. Their support gave the project practical grounding. They helped us fine-tune the trial design and navigate the approval process. Their insights - and enthusiasm - have been invaluable.

Oncode Institute: How has Oncode Institute contributed to your work?

Laura Bornes: Oncode Institute supported the extension of my PhD and has been closely involved since we got our first results. We worked together on several grant applications for the clinical study. Even when the first rounds didn’t succeed, they kept backing us. Their long-term vision and belief in the project gave us the push to keep going.