Introduction. The risk of developing subsequent primary cancers varies from 1% to 18% and it depends on the type of first cancer and treatment methods applied. Considering the time of occurrence, multiple primary cancers generally fall into two categories: synchronous and metachronous. In breast cancer patients, 10.5% developed multiple primary cancers, from which 23.8% had synchronous, 79% had metachronous and the remaining 2.8% had both synchronous and metachronous malignancies. In patients with breast cancer, elevated risk is observed especially in the development of contralateral breast cancer, endometrial cancer, esophageal cancer, ovarian cancer and thyroid cancer.

Aim. This paper presented the characteristics of breast cancer patients with metachronous primary malignancies in relation to the type of metachronous primaries (breast versus non-breast) and to analyse the impact of the type of metachronous cancers on survival rate.

Material and methods. Among patients treated for breast cancer between 1963 and 2010, 354 patients (2.1%) developed metachronous primary malignancies and these made up 13.8% of all patients with multiple primary cancers. The mean age at diagnosis of the first breast cancer was 53 ± 11.5 years; positive family cancer history was noted in 127 patients (35.9%). Metachronous malignancies are defined as primaries following the diagnosis of breast cancer in a time interval greater than or equal to than 6 months. In our group, the mean time interval between the diagnosis of breast cancer and the appearance of metachronous malignancies was 100.9 ± 74.9 months (range: 6–543 months, median: 83 months).

For comparison of the two groups (patients with second breast vs non-breast cancer) we used the Pearson’s Chi-square test for independence (for categorized variables) and variance analysis with Student’s t-test (for continuous variables). The survival rate was evaluated with the Kaplan-Meier method, and the log rank test was applied to assess the influ­ence of some factors on the evaluated results. The significance level at α = 0.05 was adopted for all statistical analyses.

Results. The probability of occurrence of new cancer averaged from 38.1% to 67.8% for 5 and 10 years after diagnosis of first breast cancer, respectively. In our group, 380 cases of metachronous carcinomas were noted in 354 analysed patients. The most frequent metachronous malignancy was breast cancer (194 cases — 54.8%), which occurred as second (192 cases) or third (2 cases) cancer. Patients with contralateral breast cancer in comparison to other types of metachronous malignancies were significantly (p < 0.05): younger (under 50 years: 56.2% vs 34.4%), premenopausal (69.6% vs 48.8%), had a lobular type of first breast cancer (6.7% vs 1.3%), and rarely received tamoxifen (25.3% vs 48.2%). The type of me­tachronous cancers significantly influenced survival rate: 10-year overall survival rates were 80.1% vs 67.8%, (p = 0.0271).

Conclusions. The risk of occurrence of second malignancies in breast cancer survivors makes early detection of metachronous malignancies obligatory because it is an important factor which influences the quality of life in breast cancer survivors.