Do site and type of metastasis in breast cancer show a changing pattern with increased age? A cross comparison of clinicopathological characteristics between age groups.

Background: In here, we evaluated pattern of metastasis and cross-compared clinicopathological features between different age groups with breast cancer (BC).

Methods: This study was conducted in the Shiraz Breast Cancer Registry (largest BC registry in Iran). Patients were classified as < 30 years old (group 1), 30-60 years old (group 2), and > 60 years old (group 3). The three age groups were compared regarding clinical and baseline characteristics.

Results: Overall, 564 individuals entered group 1, 4519 group 2, and 670 group 3. Group 1 had lower rates of tumor necrosis (p < 0.001), higher lymphatic or vascular invasion (p = 0.002), estrogen receptor-negative individuals, and HER2-positive individuals (p ≤ 0.001). Younger groups had more stage 3 BC (31.1, 25.6, and 19.7% for groups 1, 2, and 3, respectively) (p = 0.016), grade 3 BC (27.4, 20.6, and 16.5% for groups 1, 2, and 3, respectively) (p = 0.001), and grade 3 nucleus (43.1, 34.5, and 27.6% for groups 1, 2, and 3, respectively) (p < 0.001). Group 1 had higher rates of regional metastasis (4.7 vs. 1.5 and 2.1% for groups 2 and 3, respectively). Younger individuals had higher rates of brain metastasis (13.3, 5.4, and 1.1% for groups 1, 2, and 3, respectively). Moreover, those > 60 years old had more lung metastasis (33 vs. 12.6 and 6.7% for groups 2 and 1, respectively) (p < 0.001). Younger groups had more < 5-year recurrence (16.3, 11.7, and 8.9%, for groups 1, 2, and 3, respectively) (p = 0.023).

Conclusion: Pattern and site of recurrence changes according to age in BC. This brings up the question whether age is an independent predictor of organ of metastasis or is site of metastasis the result of other clinicopathological determinants which differ between age groups.