GDF-15 and Its Relationship With Treatment-related ADverse Events in Breast Cancer

GRADE is trying to find out if there is a link between a hormone called GDF-15 and the side effects that people can experience when taking T-DXd. GDF-15 can be measured in the blood. GDF-15 levels in the blood will go up when the body is stressed under certain conditions, including breast cancer. There is a link between high GDF-15 levels and the nausea and vomiting experienced with "morning sickness" in pregnancy. It has also been shown that GDF-15 levels will go up with the use of other types of chemotherapy that are known to cause nausea and vomiting. Side effects such as feeling sick (nausea), vomiting and weight loss are common with T-DXd. Sometimes, these can be so severe that treatment needs to be stopped early. The investigators can't predict who will get bad side effects and who will not. If the investigators can find out if there is a link between GDF-15 and the side effects of T-DXd, they can use this information in future clinical trials.

Growth differentiation factor 15 (GDF-15), a stress-related hormone also known as macrophage inhibitory cytokine-1 (MIC-1), is a member of the transforming growth factor-beta (TGF-β) superfamily. It is not expressed under basal conditions but can be released in response to pro-inflammatory conditions such as obesity, insulin resistance, renal and heart failure, and malignancy. Pre-clinical studies have established the role of elevated GDF-15 levels in tumour and platinum-based chemotherapy induced emesis and cachexia. It has also been proposed as a biomarker for all-cause mortality, as well as for poor prognoses in patients with cancer. The hypothesis is that there is a positive correlation between increased levels of GDF-15 and the severity of treatment-related adverse events (particularly nausea, vomiting and cachexia) experienced by patients with breast cancer receiving T-DXd. The aim of the study is to explore the relationship between relative change in levels of GDF-15 from baseline (pre-treatment) to after receiving T-DXd (post-C2 and at end of treatment) and the severity of treatment-related adverse events experienced by patients with breast cancer receiving T-DXd. If a positive relationship is found with any or all of these objectives, then monoclonal antibodies inhibiting GDF-15 (such as ponsegromab or visugromab) may present a promising therapeutic and supportive option for patients receiving T-DXd.

Inclusion Criteria: 1. Participants aged ≥18 years. 2. Histologically confirmed diagnosis of metastatic/advanced unresectable HER2-positive or HER2-low breast cancer. 3. Planned to start treatment with T-DXd. 4. Life expectancy of at least 4 months. Exclusion Criteria: 1. Current active reversible causes of decreased food intake, as determined by the Investigator. 2. Receiving tube feedings or any kind of parenteral nutrition at the time of enrolment into the study. 3. Ongoing cachexia attributable to other reasons unrelated to cancer or cancer treatment as determined by the Investigator that may confound interpretation of weight loss due to T-DXd. 4. Current adherence to a calorie-restricted diet with the intention of weight loss.