In 1982-2000, 2539 women aged 15-44 in Western Australia had a pathologically confirmed diagnosis of breast cancer. Of these, 123 (5%) had at least one pregnancy after their diagnosis and before 31 December 2004.
The median age of the women who conceived after diagnosis was 31 (interquartile range 28-35) (figure). The median age at first subsequent pregnancy was 35 (31-38). Sixty seven (56%) women had naturally conceived at least one full term pregnancy before their diagnosis. The women who had a live birth after diagnosis were generally older than women in the general population who had a live birth (table 1).
Age distribution of women with a diagnosis of breast cancer who subsequently conceived
Age matched comparison of live births in women with a previous diagnosis of breast cancer and women in general population of Western Australia, 1983-2004. Figures are numbers (percentages) of women who conceived
In total, 175 subsequent pregnancies were confirmed in the 123 women; 45 (37%) women had more than one subsequent pregnancy. Sixty six (54%) women had a live birth (table 2). Three women successfully underwent in vitro fertilisation treatment to conceive after their diagnosis; at follow-up they were alive and without recurrence. The median time from diagnosis to first subsequent pregnancy was 23 months (interquartile range 11-42). There were no still births or ectopic pregnancies. Two births occurred before 36 weeks: a set of twins at 32 weeks after spontaneous rupture of membranes and a singleton birth by caesarean section at 30 weeks when the mother developed both local and distant metastases. All children were alive and well at last follow-up.
Time from diagnosis of breast cancer to subsequent pregnancy and outcome of pregnancy. Figures are numbers of pregnancies (percentages)
Sixty two (50%) women conceived within two years of their diagnosis. Abortion was more common when conception occurred within two years of diagnosis (P=0.012) and proportionally more abortions occurred in the first six months after breast cancer was diagnosed and while the woman was undergoing active treatment (50% v 45%) (table 2). There was still a statistical difference in outcome of pregnancy between women who delayed conception two years and those who conceived within two years (P=0.021), even when we excluded women who conceived within six months of diagnosis (that is, during most adjuvant treatment) from the analysis.
Ninety five (77%) women had invasive ductal carcinoma. Tumour size ranged from 1 to 90 mm, with 58 (47%) tumours <20 mm in diameter. Tumours were reported to be oestrogen receptor (ER) positive in 29 (24%) women (42% had unknown ER status), and 79 (64%) had unaffected lymph nodes. At diagnosis stage I (n=39, 32%) or stage II (n=65, 53%) were most common (table 3).
Characteristics of tumours in 123 women with a diagnosis of breast cancer
Most women had breast conserving surgery (n=70, 57%) (table 4). These women were more likely to have radiotherapy, though 12 women had breast conserving surgery alone as local management. Only seven (6%) women were confirmed to have started hormone therapy (tamoxifen). At least one woman taking tamoxifen conceived. She stopped taking tamoxifen when the pregnancy was discovered and the pregnancy resulted in a full term live birth. No women had ovarian suppression. Three women underwent ovarian tissue preservation before treatment but conceived naturally after adjuvant chemotherapy. Fifty women (41%) had chemotherapy. The most commonly administered regimen was cyclophosphamide, methotrexate, and fluorouracil (26, 21%). A further eight (7%) women received cyclophosphamide, methotrexate, and fluorouracil in combination with doxorubicin hydrochloride and cyclophosphamide. There was no difference in age between women who received chemotherapy and those who did not. Twenty six (52%) women who had chemotherapy did not wait two years to become pregnant.
Frequency of type of treatment in management of primary breast cancer. Figures are numbers (percentages)
One hundred and four (85%) women who had a pregnancy after cancer were reported to be alive with a median follow-up of 128 months (interquartile range 80-182). All the women who died in this study died from causes related to breast cancer. Disease recurred in 48 (39%) women, with a median overall time without recurrence of 42 months (interquartile range 20-75). The five year overall survival was 92% (95% confidence interval 87% to 97%), and 10 year overall survival was 86% (80% to 93%). Five year and ten year survival from first subsequent pregnancy was 87% (81% to 93%) and 85% (78% to 91%), respectively.
The Cox's proportional hazard regression model with subsequent pregnancy as a time dependent covariate showed that subsequent pregnancy improved overall survival (hazard ratio 0.59, 95% confidence interval 0.37 to 0.95, P=0.03) (table 5). When we stratified the proportional hazard regression model by time from diagnosis, subsequent pregnancy improved overall survival in those women who waited 24 months to become pregnant (0.48, 0.27 to 0.83, P=0.009). Pregnancy had a non-significant protective effect for all women who waited at least six months to become pregnant (table 6).
Cox's proportional hazards model for survival in women with breast cancer with time dependent variable
Cox's proportional hazards model* for survival in women with breast cancer with time dependent variable stratified by time from diagnosis