ORIGINAL ARTICLE Is chemotherapy always required for cancer in pregnancy? An observational study E. M. Walsh 1 & G. M. O’Kane 1,2 & K. A. Cadoo 1,3 & D. M. Graham 1,4 & G. J. Korpanty 1 & D. G. Power 5 & D. N. Carney 1 Received: 16 December 2016 /Accepted: 24 March 2017 # Royal Academy of Medicine in Ireland 2017 Abstract Background Cancer in pregnancy is relatively rare, but the incidence is increasing. Several studies show that cytotoxic agents are safe to use in pregnancy from the second trimester onwards. Aims This study assesses the maternal and foetal outcomes of cancers diagnosed during pregnancy. In particular, it focuses on a subset of women who elected to defer systemic chemo- therapy until after delivery. This study examines if all cancers need to be treated during pregnancy or if, in certain cases, treatment can be safely deferred until after full-term delivery. Methods This is a retrospective observational study of women diagnosed with cancer during pregnancy in an Irish cancer centre over a 27-year period. All women diagnosed with can- cer during pregnancy who were referred to the medical oncol- ogy department for consideration of chemotherapy were in- cluded in this study. Medical and pharmacy records were ex- tensively reviewed. Results Twenty-five women were diagnosed with cancer in pregnancy and referred to medical oncology for consideration of systemic chemotherapy. Sixteen women (64%) com- menced chemotherapy during pregnancy, seven women (28%) did not receive chemotherapy while pregnant, but com- menced treatment immediately after delivery, and two (8%) did not receive any systemic chemotherapy at all. Of the seven women who commenced chemotherapy after delivery, six (85.7%) were diagnosed before 30/40 gestation. There were three cases of Hodgkin’ s lymphoma, two breast cancers and one ovarian cancer. After a median follow-up of 12 years, all six mothers remain disease-free. Conclusions This study identified a select cohort of patients that did not receive chemotherapy during pregnancy. There were no adverse outcomes to mothers due to delayed treatment. Keywords Cancer . Cancer in pregnancy . Chemotherapy . Outcomes . Pregnancy . Pregnancy-associated cancer Introduction Pregnancy-associated cancer describes cancer diagnosed dur- ing pregnancy or up to 12 months after delivery [ 1]. Pregnancy-associated cancer is relatively rare, occurring in ~1 in 1000–2000 pregnancies [1–4]. This translates to approx- imately 2500–5000 cases diagnosed per year in Europe, 5000 cases per year in North America [5] and an estimated 60–70 cases per year in Ireland. With the current trend of delaying pregnancy [6] and an age-dependent increases in several ma- lignancies [7], an increase in pregnancy-associated cancers can be expected [1, 8, 9]. The term cancer in pregnancy de- scribes cancers diagnosed during pregnancy, but excludes those diagnosed in the postpartum setting, which account for * E. M. Walsh elaine1walsh@gmail.com 1 Department of Medical Oncology, Mater Misericordiae University Hospital, Dublin, Ireland 2 Division of Medical Oncology and Hematology, Princess Margaret Cancer Centre, University of Toronto, Toronto, ON, Canada 3 Breast Cancer Medicine Service, Memorial Sloan Kettering Cancer Center and Weill Medical College of Cornell University, New York, NY, USA 4 Centre for Cancer Research and Cell Biology, Queen’ s University Belfast, Belfast, UK 5 Department of Medical Oncology, Cork University Hospital and Mercy University Hospital, Cork, Ireland Ir J Med Sci DOI 10.1007/s11845-017-1602-3