Recent data presented at the 2024 ASCO Annual Meeting highlights the potential of glucagon-like peptide-1 (GLP-1) agonists, such as semaglutide and tirzepatide, in managing weight gain, a common adverse effect in breast cancer patients. A retrospective study conducted at Memorial Sloan Kettering Cancer Center suggests that these drugs could play a significant role in improving patient outcomes by addressing weight-related complications.
Weight Gain as an Adverse Event in Breast Cancer
Weight gain is a prevalent issue among breast cancer patients, often induced by chemotherapy and endocrine therapy. Chemotherapy can lead to weight gain due to fluid administration, steroid use, and altered eating habits. Endocrine therapy, including tamoxifen and aromatase inhibitors, also contributes to weight gain, particularly in hormone receptor-positive breast cancer patients, who constitute 70% to 80% of all breast cancer cases.
Sherry Shen, MD, a breast medical oncologist at Memorial Sloan Kettering Cancer Center, noted, "Weight gain is a very common AE for many of our patients with breast cancer... Beyond chemotherapy, endocrine therapy pills, notoriously, can cause weight gain."
Retrospective Study Findings
The retrospective study aimed to evaluate the impact of GLP-1 agonists on weight management in breast cancer patients. The study included 75 patients with a history of breast cancer who were prescribed a GLP-1 agonist for either weight management or diabetes. The primary outcome was the degree of weight loss achieved with these medications.
The study found that patients experienced an average weight loss of 5% with GLP-1 agonists. Weight loss was correlated with the duration of treatment; at six months, patients lost over 2 kg, and at 12 months, they lost over 4 kg. By the end of the treatment, the average weight loss exceeded 6 kg. The analysis did not reveal any significant associations between the type of breast cancer, endocrine therapy, or diabetes status and the extent of weight loss.
"What we found was that the average weight loss was about 5% with a GLP-1 agonist and that the longer patients were on the GLP-1 agonist, the more weight they tended to lose," Dr. Shen explained.
GLP-1 Agonist Usage and Considerations
The study also examined the types of GLP-1 agonists used. Liraglutide was used by 49% of patients, semaglutide by 60%, exenatide by 17%, dulaglutide by 8%, and tirzepatide by 11%. Many patients (almost half) switched between different GLP-1 agonists during the study period. It's important to note that nearly 80% of patients were prescribed GLP-1 agonists for diabetes management rather than solely for weight loss.
Implications for Clinical Practice and Future Research
While breast medical oncologists typically do not prescribe GLP-1 agonists themselves, there is growing recognition of their potential role in managing adverse events and improving breast cancer outcomes. Post-breast cancer diagnosis weight gain is associated with worse outcomes, and lifestyle trials have shown that significant weight loss can lead to modest improvements in these outcomes. Further research is needed to rigorously study the use of GLP-1 agonists in clinical trials for breast cancer patients.
Dr. Shen emphasized the need for further investigation: "There is a role to study these drugs for AE management, especially our patients on endocrine therapy. But in addition, with managing that AE, with decreasing the degree of weight gain that happens post diagnosis, perhaps there can be an effect on breast cancer outcomes."
However, the increasing use of GLP-1 agonists for weight loss in the general population raises considerations for clinical trial design, including drug availability and patient selection. These factors must be carefully addressed to ensure the successful integration of GLP-1 agonists into breast cancer treatment strategies.
