Differential Diagnosis for Low-Grade Fever 2 Weeks After Radiation Therapy for Breast Cancer
Single Most Likely Diagnosis
- Radiation pneumonitis: This is a common side effect of radiation therapy, especially when the treatment field includes the lungs. The onset of symptoms, including low-grade fever, can occur weeks to months after completion of radiation therapy, making it a likely cause in this scenario.
Other Likely Diagnoses
- Infection: Bacterial, viral, or fungal infections can occur after radiation therapy due to immune system suppression or disruption of mucosal barriers. Common sites of infection include the urinary tract, lungs, and skin.
- Fatigue and stress-related fever: Radiation therapy can cause significant physical and emotional stress, leading to fatigue and potentially low-grade fever.
- Hormonal therapy side effects: If the patient is on hormonal therapy (e.g., tamoxifen or aromatase inhibitors) as part of their breast cancer treatment, side effects such as hot flashes or night sweats could potentially cause a low-grade fever.
Do Not Miss Diagnoses
- Neutropenic fever: Although less common 2 weeks after radiation therapy, if the patient has received concurrent chemotherapy or has a history of bone marrow suppression, neutropenic fever is a life-threatening condition that requires immediate attention.
- Sepsis: Any sign of infection in a patient who has recently undergone radiation therapy should prompt consideration of sepsis, especially if there are other symptoms such as tachycardia, tachypnea, or hypotension.
- Pulmonary embolism: While not directly related to fever, pulmonary embolism is a potential complication in cancer patients and can present with nonspecific symptoms. A high index of suspicion is necessary, especially if there are respiratory symptoms.
Rare Diagnoses
- Radiation-induced lung fibrosis: Although this typically presents later than 2 weeks post-radiation and is more commonly associated with symptoms like cough and shortness of breath, it could potentially cause a low-grade fever in its early stages.
- Lymphoma or leukemia: Very rare complications of radiation therapy, but they could potentially present with fever among other symptoms.
- Thyroiditis: Radiation therapy can cause thyroid dysfunction, including thyroiditis, which might present with fever, though this is less common.