Decreased hormonal sensitivity after childbirth rather than the tumor size influences the prognosis of very young breast cancer patients

Purpose: There is a significant difference in the mean tumor size between very young breast cancer patients and their elder counterparts. A simple comparison may show obvious prognostic differences. We investigated the prognostic impact of age by reducing the influence of the tumor size, which is thought to be a confounding factor.

Patients and methods: We investigated 1,880 consecutive pT1-4N0-3M0 breast cancer patients treated at less than 45 years of age between 1986 and 2002 and conducted a case-control study of breast cancer subjects less than 30 years of age. Each patient (Younger than 30) was matched with a corresponding control subject (Elder counterpart) based on an age 15 years above the patient's age, a similar tumor size and a status of being within 1 year after surgery. In addition, we assessed 47 patients with pregnancy-associated breast cancer (PABC). The levels of hormone receptors were measured using an enzyme immunoassay (EIA), and receptor-positive cases were divided into "weakly" and "strongly" positive groups based on the median value. Years from the last childbirth (YFLC) was categorized as "recent" and "past" at the time point of 8 years.

Results: There were fewer past YFLC cases, more partial mastectomy cases, a higher rate of scirrhous carcinoma or solid-tubular carcinoma in the Younger than 30 group than in the Elder counterpart group. The rates of a PgR-negative status in the Younger than 30 and Elder counterpart groups were 45.1 and 29.9%, respectively, As for the relationship between the PgR-negative rate and YFLC, the rates of a PgR-negative status in the past YFLC, nulliparous, recent YFLC and PABC groups were 31.9, 37.7, 44.4 and 65.7%, respectively. On the other hand, the rates of strongly positive cases were 42.6, 30.2, 22.2 and 8.6%, respectively. The 10-year recurrence-free survival rates in the Younger than 30, Elder counterpart and PABC groups were 61.7, 65.6 and 54.1%, respectively. The differences between the groups were not significant. In a multivariate analysis, independent prognostic facers included the number of lymph node metastases (4-9, HR:3.388, 95% CI 1.363-8.425, p = 0.0086, over 10, HR: 6.714, 2.033-22.177, p = 0.0018), solid-tubular carcinoma (HR 3.348, 1.352-8.292, p = 0.0090), scirrhous carcinoma (HR 2.294, 1.013-5.197, p = 0.0465) and past YFLC (HR 0.422, 0.186-0.956, p = 0.0387). An age younger than 30 was not found to be an independent prognostic factor.

Conclusions: The prognosis of the very young women was the same as their elder counterparts with a matched tumor size, and age was not identified to be an independent prognostic factor according to the multivariate analysis. Recent childbirth probably influences the prognosis of patients younger than 30 years of age with breast cancer by lowering hormonal sensitivity.