Case Report: Prolonged thrombocytopenia after chemotherapy in solid tumors requiring long-term thrombopoietin receptor agonist support: a five-patient case series.

Chemotherapy-induced thrombocytopenia (CIT) is a clinically significant complication of systemic anticancer therapy. Although CIT is commonly classified as nadir CIT or persistent CIT based on the timing and pattern of platelet recovery, prolonged thrombocytopenia after chemotherapy discontinuation remains poorly characterized. We report a retrospective case series of five patients with solid tumors who developed prolonged thrombocytopenia after chemotherapy discontinuation. Despite conventional supportive measures, platelet counts (PCs) failed to recover adequately; all patients subsequently received long-term thrombopoietin receptor agonist (TPO-RA) therapy to maintain PCs. TPO-RA supportive treatment was maintained for 7 to 22 months. Bone marrow (BM) examinations consistently demonstrated reduced or absent megakaryocytes, whereas overall hematopoietic activity ranged from relatively preserved to hypoplastic. At last follow-up, all patients were alive. No bleeding or thrombotic events were observed after discontinuation of anticancer therapy, and no clinically apparent TPO-RA-related adverse events were documented during treatment. One patient resumed anticancer therapy while receiving TPO-RA support, whereas the remaining four received no further anticancer treatment. This case series characterizes an understudied pattern of prolonged impairment of platelet recovery after chemotherapy that may require sustained thrombopoietic support. Larger prospective longitudinal studies are needed to clarify the underlying heterogeneity and identify patients most likely to require prolonged TPO-RA therapy.