Prevalence of Chemotherapy-Induced Thyroid Dysfunction in Breast Cancer and Lymphoma

Background: In cancer cases, thyroid function is thought to be vulnerable to chemotherapy, as hypothalamic-pituitary axis is active and chemotherapy is systemic therapy for cases. This investigation aimed to evaluate the effect of chemotherapy on thyroid function, thyroid function alters during toxicity of chemotherapy, and the predictive value of thyroid function on pathological complete response (pCR) in cases with early breast cancer (BC) or lymphoma receiving chemotherapy. Methods: This prospective investigation included a total of 50 cases, 25 with BC and 25 with lymphoma. All studied cases were subjected to routine laboratory investigations [Complete blood count, Random blood sugar, Thyroid function tests (TSH, fT3 & fT4), kidney and liver function tests] and Imaging: Thyroid ultrasound. Results: Chemotherapy regimens showed varying associations with thyroid dysfunction. The Taxol /Carboplatin regimen was linked to a significantly higher dysfunction rate (66.7%, p = 0.023 vs. others), whereas R-CHOP had a markedly lower rate (7.7%, p = 0.001 vs. others). Chemotherapy induced significant hematologic alterations. Hemoglobin levels declined (p = 0.008), and white blood cell (WBC) counts dropped (p < 0.001). Conclusion: Chemotherapy exerts a measurable and comparable impact on thyroid function in cases with early-stage BC and lymphoma, independent of cancer type, with specific chemotherapeutic agents—particularly taxane-based regimens—being associated with a higher incidence of thyroid dysfunction, underscoring the need for proactive thyroid monitoring tailored to treatment protocols rather than cancer treatment alone.