Background
Nonmetastatic non-inflammatory invasive breast cancers having skin involvement (SI) are classified as T4b, regardless of size. This study evaluated disease specific survival (DSS) to determine whether size should be considered for these lesions, rather than grouping them all into Stage III.
Study Design
Surveillance Epidemiology and End Results data linked to Medicare claims were reviewed. SI and nonSI tumors were reclassified using AJCC 7th Edition groupings using tumor size and nodal involvement alone without considering SI (neostage). DSS was adjusted for demographics, histology and treatment using competing risk methods with propensity score-based weighting and bootstrap standard errors.
Results
Among 924 SI patients diagnosed between 1992 and 2005, tumors were 0.1–2.0, 2.1–5.0, and >5.0 cm in 11.6%, 51.1%, and 37.3% of cases, respectively. There were no nodal metastases in 22.3%, 1–3 positive nodes in 31.7%, 4–9 positive in 28.6% and ≥10 positive in 17.4% of cases. For SI patients, adjusted 5-year DSS was 95.8% [95%CI: 95.6–96.0] for neostage I, declining progressively to 36.4% [95%CI: 33.8–39.2] for neostage IIIC patients. Adjusted 5-year DSS for SI and nonSI tumors (n=66,185) was similar for neostage I, IIA, and IIB, and markedly lower for IIIA and IIIC. Adjusted DSS for SI IIIA was similar to nonSI IIIC.
Conclusions
Noninflammatory SI breast cancers have widely varied DSS that differs by tumor size and nodal involvement, and therefore should not all be stage III. SI should be subordinate to T and N groupings to classify SI with nonSI lesions having similar prognoses.