Prognostic impact of second cancer on the survival of early breast cancer patients

Although numerous reports have been published on the incidence of second ca ncers after adjuvant therapy for early breast cancer, there have been few s tudies on the effect of the development of second cancer on overall surviva l (OS) of the patients. 1857 female patients younger than 80 years of age w ith operable breast cancer with UICC Stages I, II, and III who entered 3 tr ials of adjuvant therapy were studied for the detection of recurrence and s econd cancer. The median follow-up period for surviving patients was 12 yea rs (range, 5-25 years). 384 of recurrence and 119 of second cancers occurre d. 465 deaths were recorded, the causes of which were designated to be due to recurrence of breast cancer in 326 patients, second cancers in 57, and d ue to other causes in 82. Many background factors that were significantly r elated to recurrence did not influence the incidence of and death by second cancers after mastectomy: age and menopausal status alone were related. Th e difference in the Kaplan-Meier curves between the event (recurrence and s econd cancers)free and relapse-free survivals indicates the incidence of se cond cancers is a significant event in post-operation course of early breas t cancer patients (P=0.0001). The survival curve of patients who were free from recurrence- and second ca ncer-death is shown to be significantly lower than that of those free from breast cancer-specific death (P=0.0355), suggesting that death by second ca ncers is significantly influential to the overall survival. According to th e Cox regression model using a recurrence or second cancers as time-depende nt variables, the diagnosis of a recurrence or second cancer is shown to be highly significant to OS of the patients (hazard ratio: 49.3, and 6.3, res pectively). Second cancers are shown to be not statistically significantly influential to the breast cancer specific survival (P=0.0637), nor a recurr ence to second cancer specific survival (P=0.2285). In spite of heterogeneo us distribution of sites of second primary cancers and their different natu ral histories, the incidence of second cancer has a significant effect on t he postoperative survival of early breast cancer patients. In the survival analysis of early breast cancer patients, we have to estimate the contribut ion of second cancers to properly evaluate the effect of treatment.