Prognostic implications of lobular breast cancer histology: new insights from a single hospital cross-sectional study and SEER data

Background: Invasive lobular breast cancer (ILC) is generally believed to have an increased risk for late relapse compared to invasive ductal breast cancer (IDC). However, the study most often referred to is a chemotherapy trial that mainly included node positive patients. We hypothesize that nodal status may influence the hazard of relapse since time of diagnosis differently in invasive ductal carcinoma (IDC) and ILC.

Methods: Primary operable breast cancer patients from our institution diagnosed between 2000 and 2009 were studied. Multivariable analysis and subgroup analyses were performed to assess whether ILC carries a different prognosis compared to IDC. SEER data were used for external validation.

Results: In lymph node negative patients, ILC carries a better prognosis regarding distant metastasis free interval (DMFI) (HR 3.242 (1.380-7.614), p = 0.0069) with a trend towards improved breast cancer specific survival (BCSS), over the entire study frame (UZ Leuven data). In lymph node positive patients, both DMFI (HR 0.466 (0.309-0.703), p = 0.0003) and BCSS (HR 0.441 (0.247-0.788), p = 0.0057) are significantly worse for ILC, especially after longer follow-up (>4-5 years) (UZ Leuven data). Similar results were found in the SEER cohort. Results remained identical when excluding screen detected cases (data not shown).

Conclusion: The prognostic impact of lobular histology not only depends on time since diagnosis but also on nodal status. The general believe that ILC have compromised late-term outcome compared to IDC seems untrue for the majority ( = node negative) of ILCs.