Impact of trimester of diagnosis on tumor characteristics and survival in breast cancer during pregnancy

Breast cancer diagnosed during pregnancy (PrBC) more often shows unfavorable disease characteristics compared to breast cancer in non-pregnant young patients. The STURGATE collaboration in Sweden and The Netherlands investigated the impact of trimester of diagnosis on tumor characteristics and survival in PrBC. PrBC patients were matched for age and year of diagnosis to three non-PrBC patients (controls) per country. PrBC patients diagnosed in the first trimester of pregnancy resembled the non-PrBC controls, whereas second and third trimester diagnoses were associated with significantly more aggressive features, including higher rates of triple-negative subtype, higher histological grade, and more advanced stage at presentation compared to controls. After adjustment for these features and treatment, overall survival remained significantly worse in PrBC patients compared to non=PrBC controls. This association was pronounced in the second and third trimesters, but did not reach statistical significance after full adjustments. The authors conclude that these data suggest trimester-specific biological influences on tumor behavior and survival.