Validating a prognostic scoring system for postmastectomy locoregional recurrence in breast cancer.

Purpose: This study is designed to validate a previously developed locoregional recurrence risk (LRR) scoring system and further define which groups of patients with breast cancer would benefit from postmastectomy radiation therapy (PMRT).

Methods And Materials: An LRR risk scoring system was developed previously at our institution using breast cancer patients initially treated with modified radical mastectomy between 1990 and 2001. The LRR score comprised 4 factors: patient age, lymphovascular invasion, estrogen receptor negativity, and number of involved lymph nodes. We sought to validate the original study by examining a new dataset of 1545 patients treated between 2002 and 2007.

Results: The 1545 patients were scored according to the previously developed criteria: 920 (59.6%) were low risk (score 0-1), 493 (31.9%) intermediate risk (score 2-3), and 132 (8.5%) were high risk (score ≥4). The 5-year locoregional control rates with and without PMRT in low-risk, intermediate-risk, and high-risk groups were 98% versus 97% (P=.41), 97% versus 91% (P=.0005), and 89% versus 50% (P=.0002) respectively.

Conclusions: This analysis of an additional 1545 patients treated between 2002 and 2007 validates our previously reported LRR scoring system and suggests appropriate patients for whom PMRT will be beneficial. Independent validation of this scoring system by other institutions is recommended.