Fatigue is common in early-stage breast cancer, but it often reflects overlapping multidriver symptom clusters rather than a single cause. Melinda L. Telli, MD, FASCO, describes how sleep disturbance, vasomotor symptoms, pain, neuropathy, and anxiety can interact, providing insights into why targeted questions and proactive side effect troubleshooting can improve function while supporting treatment adherence.

In early-stage breast cancer, there are certainly symptoms that cluster. Fatigue is a common complaint that we hear from our patients with ER+ early-stage breast cancer. The question is: What is driving the fatigue for this patient? For example, is this a 35-year-old woman who was started on ovarian suppression therapy and is having difficulty with nighttime vasomotor symptoms, leading to interrupted sleep and daytime fatigue? Those things can cluster together if patients have severe nighttime vasomotor symptoms.

Then there are other patients who are really destabilized by a breast cancer diagnosis. For example, more than 80% of patients with breast cancer will have a sleep disturbance after the initial diagnosis, which, unfortunately, becomes a chronic issue in up to 33% of individuals. Some of these patients may have fatigue because they are not sleeping well, with the main driver being a mood disorder or prominent anxiety about their treatment, diagnosis, and future, as well as the impacts on their work and family.

Pain is another important symptom in patients with breast cancer. Patients may have severe neuropathy from paclitaxel chemotherapy, which can interfere with sleep. Or some patients have had extensive surgeries for breast cancer, such as a bilateral mastectomy with reconstruction, and this can cause chronic chest wall pain, preventing them from getting into a comfortable position at night. We see all these things in clinical practice.

Ultimately, recognizing the cause of a patient’s symptoms is important. When a patient comes in and says, “I do not know what is wrong with me—I am just so tired,” we should probe that. One of my first questions in response to a statement like this is, “How is your sleep?” If a patient says that their sleep is bad, then my next questions are, “Why is it bad? Is it that you are waking up with hot flashes all night? Are you in pain? Are you ruminating and cannot quiet your mind?” Poor sleep is really a foundational kind of symptom.

A lot of the challenging symptoms that patients with early breast cancer report are multifactorial. Patients may have several things colliding at the same time (eg, coming off chemotherapy and surgery and carrying symptoms from that and/or starting endocrine therapy and having symptoms exacerbated from that). Patients frequently do not like the way they feel on endocrine therapy, and this raises the concern that they will not adhere to treatment. For instance, some will take their medication but will not adhere to the regimen as prescribed. Other times, patients are noncompliant and stop the treatment. It is tragic when patients in these scenarios come back with metastatic disease.

If a patient with breast cancer is having issues during treatment, it is important for them to let us know. There are many side effects that we can try to mitigate. It is important to tell the patient before they start treatment, “If you are having problems, we are going to be here, and we will troubleshoot them together.” Sometimes this may mean that we are going to try a different drug, but it is always worth explaining the importance and the benefit of therapy in terms of its impact on long-term outcome.