Influence of pregnancy on the outcome of breast cancer: A case‐control study

Abstract

The relationship between pregnancy and the outcome of breast cancer remains controversial. The purpose of this study was to determine the prognostic value of pregnancy at the time of diagnosis of primary infiltrating breast cancer. In a retrospective multi-center study we compared a group of 154 patients presenting pregnancy-associated (PA) breast cancer with a control group of 308 patients presenting non-pregnancyassociated (non-PA) breast cancer. Classic prognostic factors, treatment modalities, disease-free survival and overall survival were compared in the 2 groups. The relative importance of pregnancy was assessed by Cox multivariate analysis. There was a significantly higher proportion of inflammatory breast cancer, large tumors and negative receptor status in the PA group. Five-year recurrence-free survival, metastasisfree survival and overall survival were lower both in the whole PA group and in the PA sub-group excluding patients with inflammatory breast cancer than in the corresponding non-PA groups. According to clinical stage, histoprognostic grade and microscopic lymph-node involvement, probability of 5-year metastasis-free survival and overall survival was lower in the PA group. Outcome was significantly poorer after chemotherapy for patients in the PA sub-group than in the non-PA sub-group. Multivariate analysis demonstrated that pregnancy was an independent and significant prognostic factor. Pregnancy has an adverse effect on the outcome of breast cancer. Concurrent or recent pregnancy should be taken into account in the development of new systemic therapies. Our findings have important implications for further research into the basic mechanisms of cancer. Int.

Pregnancy-associated breast cancer

“…A study by Bonnier et al (9), in addition to other studies, suggested that pregnancy may be an independent prognostic factor. This was a multi‐institutional study carried out in 23 French institutions.…”

“…The majority of PABCs are high grade and lymphovascular invasion is often present, characteristics that are similar to those seen in young non‐pregnant breast cancer patients (7,8). However, when further histological comparisons are made with non‐pregnant controls, studies show that tumors in PABC are 1.5–2 times more often over 2 cm in diameter and lymph node‐positive, and 2.5 times more often associated with distant metastases at diagnosis (9–12). It is unknown whether this is caused by a more aggressive growth pattern due to the biological effects of pregnancy, to delayed diagnosis, or to a combination of the two (13).…”

“…Estrogen receptor status is strongly associated with age at diagnosis in breast cancer and postmenopausal breast cancer patients are receptor‐positive in over 77% of cases compared to 23% in premenopausal patients (14). Hormone receptor status in PABC has been assessed in several studies (9,14,15) and although the results vary, several studies have shown significantly decreased levels of expression compared to age‐matched controls (16) beyond what would be expected by age alone. In a study by Bonnier et al (9), 75 PABC patients were compared to 182 non‐pregnant age‐matched women.…”

“…Hormone receptor status in PABC has been assessed in several studies (9,14,15) and although the results vary, several studies have shown significantly decreased levels of expression compared to age‐matched controls (16) beyond what would be expected by age alone. In a study by Bonnier et al (9), 75 PABC patients were compared to 182 non‐pregnant age‐matched women. In the PABC group, estrogen (ER) and progesterone receptor (PR) negativity was seen in 41.9% of the women compared to 21.3% in the control group ( p = 0.002).…”

“…Earlier studies proposed that the pregnancy itself may be an independent prognostic factor for survival in patients with PABC (9,73,74). Advocates of this hypothesis have suggested that the apparent increased vascularity of the breast during pregnancy, the high circulating levels of hormones, and the immune‐suppressed state of pregnancy may accelerate the course of the cancer.…”