The Impact of Subtype Distribution in Inflammatory Breast Cancer Outcome

Inflammatory breast cancer (IBC) has an unfavourable prognosis despite the advances made in the treatment of breast cancer. Our study aimed to define immunohistochemistry-based surrogate subtype distribution to determine whether the breast cancer subtype accompanied survival outcome differences in IBC.

Medical records of female breast cancer patients with non-metastatic inflammatory breast cancer admitted to our clinic between March 2000 and December 2015 were retrospectively reviewed. Patient demographics, clinical and pathological feature of the primary tumour, adjuvant treatment options and survival data were analysed. Intrinsic breast cancer subtypes were defined according to ER, PR, HER-2 and ki-67 status.

We identified 129 non-metastatic inflammatory breast cancer patients. Median follow-up was 73 months. 10 (7.7%) were luminal A-like, 67 (51.9%) were luminal B-like, 37 (28.6%) were HER-2 positive, and 15 (11.6%) were triple negative (TNBC) by immunohistochemistry. There were no statistically significant differences between subtypes in terms of histological type, grade, tumour size and lymph node status. Median disease-free survival was 47 months (95% confidence interval [CI] 29.2-82.6) and median overall survival was 75 months (95% CI 64.7-90.8). Triple negative breast cancer showed poorer outcome than other subgroups. Presence of TNBC disease was associated with poorer outcome compared to luminal A (HR: 0.19, 95% CI 0.04-0.92, p: 0.039), luminal B (HR: 0.34, 95% CI 0.15-0.74, p: 0.007) and HER-2 positive subgroups (HR: 0.40, 95% CI 0.17-0.94, p:0.037). Luminal A patients had a trend to have a better overall survival which did not reach to a statistical significant difference.

Our study put forth that IBC have a poor prognosis irrespective of breast cancer surrogate subtype distribution. Luminal A, the most frequent subtype of breast cancer was the least common in our IBC patient group. TNBC had the worst outcome when compared to other breast cancer subtypes.