does subsequent pregnancy influence breast cancer survival?

PURPOSE: The influence of subsequent pregnancy following breast cancer diagnosis and treatment is an issue of much concern among young patients. Given the current patterns of delayed childbearing, many young breast cancer patients are questioning the safety of subsequent pregnancy. This collaborative investigation further explores this relationship. METHODS: A retrospective case-case study utilizing data abstracted from medical records maintained by Kaiser Permanente enabled comparison of the hazard of recurrence and breast cancer death among 105 women with one or more pregnancies following diagnosis and 335 matched cases without a subsequent pregnancy. Matching criteria included: stage at diagnosis and at time of first subsequent pregnancy, age [± 8], and year [± 8] of diagnosis, and survival time from diagnosis to first subsequent pregnancy. Kaplan-Meier curves were generated to compare time to recurrence and death due to breast cancer among cases with and without a history of subsequent pregnancy. Matched Cox regression models were constructed to assess the risk of recurrence and death controlling for family history of breast or ovarian cancer, estrogen and progesterone receptor status, prior pregnancy history, adjuvant radiation and chemotherapy. RESULTS: Among the 440 young cases [mean age 34 years], reproductive history at diagnosis was similar for women with and without a subsequent pregnancy; 20% were nulliparous. Records indicated that 49% [51/105] of subsequent pregnancies were interrupted. Kaplan-Meier analysis indicated no significant differences in time to recurrence or death by subsequent pregnancy status. Similarly, the matched Cox proportional hazards models revealed the risk of recurrence [1.4 (0.6,3.3)] and breast cancer death [0.97 (0.3,3.0)] was not influenced by subsequent pregnancy history. CONCLUSION: The risk of recurrence or breast cancer death is similar for young cases regardless of subsequent pregnancy history.