Clinicopathologic characteristics and prognosis of breast cancer patients associated with pregnancy and lactation were clarified by means of a case‐control study of matched non‐pregnant and non‐lactating patients with breast cancer. From 18 institutions in Japan, a total of 192 subjects with breast cancer diagnosed during pregnancy (72 cases) and lactation (120 cases) were collected between 1970 and 1988, accounting for 0.76% of all breast cancer patients. The duration of symptoms was longer and tumor size was larger in the study subjects. Although the disease‐free interval was longer than that in the control patients, the survival time was shorter. There was no characteristic difference in histologic type. Vascular invasion and lymph node metastasis were found more frequently in the subjects. The positive rates of estrogen receptor and progesterone receptor were lower in the subjects. The 5‐ and 10‐year survival rates of the study patients were 65% and 55%, respectively, and these survivals were significantly lower than those of the control (P < 0.001). The survival rates were poorer in the subjects, in accordance with stage and lymph node metastasis. The results suggest that most of the patients with breast cancer diagnosed during pregnancy and lactation are in a more advanced stage because of a delay in detection and diagnosis, and hence have unfavorable prognosis. Therefore, it is important to diagnose and treat early for improvement of prognosis in patients with breast cancer during pregnancy and lactation.

To investigate the relationship between the tumor growth rate of the primary breast cancer and its prognosis, records for 122 breast cancer patients in 9 hospitals in Japan were retrospectively reviewed. These records contained at least two measurements of the same tumor mass in the breast. So the growth rate was estimated from these measurements taken at different points in time. The doubling time of the breast tumors showed an approximately log‐normal distribution. The geometric mean of doubling times for all cases was 174 days. The solid‐tubular histologic type of carcinoma had the shortest geometric mean of doubling time (126 days), the scirrhous carcinoma had the second shortest one (205 days), and the papillotubular carcinoma had the longest one (252 days). The patients with shorter doubling time of tumor tended to have a poorer prognosis. The Cox multiple regression analysis showed that the tumor growth rate was related significantly with survival, after adjusting for other covariates such as clinical stage, lymph node metastasis, age of patient, histological type, and year of treatment.

To study the effects of family history and reproductive, anthropometric, and dietary factors on the risk of breast cancer among low risk populations, we conducted a hospital-based case-control study involving 908 patients with breast cancer and their matched controls, in Japan. A positive family history of breast cancer significantly increased the risk of breast cancer (odds ratio = 1.52, 95% confidence interval: 1.14-2.03). The risk further increased with increasing number of family members affected. Obesity, single marital status, fewer births, a late childbirth, and less consumption of green-yellow vegetables and dairy products were also associated with an increased risk of breast cancer. These associations were independent in multivariate analyses. There was no increase in risk associated with consumption of high fat foods. When analyzed by menopausal status, the association with family history of breast cancer, especially in the first degree of relatives, was more evident for premenopausal breast cancer. The associations with obesity and lower consumption of dairy products were more pronounced for postmenopausal breast cancer, while those with lower parity and single marital status were stronger for premenopausal breast cancer.

Continuous elevation of IL-6 levels indicates poor prognosis in heavily pretreated patients with recurrent breast cancer. Combination therapy including agents that reduce IL-6 levels will be a new strategy for aggressively treating recurrent breast cancer.

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