Risk of secondary hematologic malignancies associated with breast cancer chemotherapy and G-CSF support: A nationwide population-based cohort.

Our study aimed to analyze the risk of hematologic malignancies (HM) associated with the use of G-CSF with chemotherapy for BC. Using the French National Health Data System, we examined the HM risks in patients diagnosed with an incident breast cancer between 2007 and 2015, who received chemotherapy for BC. Main outcomes were acute myeloid leukemia (AML), Myelodysplastic syndrome (MDS), myeloproliferative neoplasms (MPNs), multiple myeloma (MM), Hodgkin lymphoma or non-Hodgkin lymphoma (HL/NHL) and acute lymphoblastic leukemia or lymphocytic lymphoma (ALL/LL). Among a total of 122 373 BC survivors, 38.9% received chemotherapy only and 61.1% received chemotherapy + G-CSF. Overall, 781 cases of hematologic malignancies occurred. We observed a nonsignificant increase in the risk of AML (aHR, 1.3; 95% CI, 1.0-1.7), of MDS (aHR, 1.3; 95% CI, 0.9-1.8) and of ALL/LL (aHR, 2.0; 95% CI, 1.0-4.4) among patients treated by chemotherapy + G-CSF compared to chemotherapy only. In analyses by dose, we observed a slight increase in the risk of AML (1-3 doses: aHR, 1.2; 95% CI, 0.8-1.7/4+ doses: aHR, 1.3; 95% CI, 1.0-1.8) and of MDS (1-3 doses: aHR, 1.1; 95% CI, 0.7-1.7/4+ doses: aHR, 1.4; 95% CI, 1.0-1.9), a significant increase in risk of ALL (1-3 doses: aHR, 1.5; 95% CI, 0.5-3.9 / 4+ doses: aHR, 2.3; 95% CI, 1.0-5.1) with increasing cycles of G-CSF. Our population-based study showed that the ALL/LL was the only HM at increased risk with the use of growth factors with a possible dose-effect relationship. Our data regarding the risk of all the other HM are reassuring.