Male breast cancer: correlation between immunohistochemical subtyping and PAM50 intrinsic subtypes, and the subsequent clinical outcomes.

Male breast cancer is a rare disease that is still poorly understood. It is mainly classified by immunohistochemistry as a luminal disease. In this study, we assess for the first time the correlation between molecular subtypes based on a validated six-marker immunohistochemical panel and PAM50 signature in male breast cancer, and the subsequent clinical outcome of these different subtypes. We collected 67 surgical specimens of invasive male breast cancer from four different Spanish pathology laboratories. Immunohistochemical staining for the six-marker panel was performed on tissue microarrays. PAM50 subtypes were determined in a research-use-only nCounter Analysis System. We explored the association of immunohistochemical and PAM50 subtypes. Overall survival and disease-free survival were analyzed in the different subtypes of each classification. The distribution of tumor molecular subtypes according PAM50 was: 60% luminal B, 30% luminal A and 10% human epidermal growth factor receptor 2 (Her2) enriched. Only one Her2-enriched tumor was also positive by immunohistochemistry and was treated with trastuzumab. None of the tumors were basal-like. Using immunohistochemical surrogates, 51% of the tumors were luminal B, 44% luminal A, 4% triple-negative and 1% Her2-positive. The clinicopathological characteristics did not differ significantly between immunohistochemical and PAM50 subtypes. We found a significant worse overall survival in Her2-enriched compared with luminal tumors. Male breast cancer seems to be mainly a genomic luminal disease with a predominance of the luminal B subtype. In addition, we found a proportion of patients with Her2-negative by immunohistochemistry but Her2-enriched profile by PAM50 tumors with a worse outcome compared with luminal subtypes that may benefit from anti-Her2 therapies.

Proliferation Determined by Ki-67 Defines Different Pathologic Response to Neoadjuvant Trastuzumab-Based Chemotherapy in HER2-Positive Breast Cancer.

BACKGROUND: This study aimed to assess the role of proliferation measured by Ki-67 as a predictive factor for pathologic complete response (pCR) to trastuzumab-based chemotherapy in patients with human epidermal growth factor receptor 2 (HER2)-positive (HER2(+)) breast cancer (BC). METHODS: A total of 81 patients with HER2(+) BC were treated with a sequential schedule consisting of 4 cycles of cyclophosphamide (600 mg/m(2)) and doxorubicin (60 mg/m(2)) every 3 weeks, followed by 4 cycles of weekly paclitaxel (80 mg/m(2)) or docetaxel (100 mg/m(2)) every 3 weeks combined with trastuzumab (loading dose of 8 mg/kg and then 6 mg/kg every 3 weeks) as neoadjuvant treatment. Histologic subgroups classified by hormone receptor (HR) expression and Ki-67 index were 17% HR(+)/Ki-67 ≥ 50%, 41% HR(+)/Ki-67 < 50%, 25% HR-negative (HR(-)) Ki-67 ≥ 50%, and 17% HR(-)/Ki-67 < 50%. RESULTS: pCR, defined as the absence of invasive cells in the breast and axillary lymph node, was achieved in 33 patients (41%). The median Ki-67 expression was significantly higher in tumors with pCR (53%) compared with tumors without pCR (30%) (P < .001). Receiver operating characteristic (ROC) curve methodology suggested that 50% was the optimal Ki-67 cutoff point to best identify patients who achieved a pCR. The pCR rate was significantly different between histologic subgroups: HR(-)/Ki-67 ≥ 50% (70%), HR(+)/Ki-67 ≥ 50% (71%), HR(-)/Ki-67 < 50% (22%), and HR(+)/Ki-67 < 50% (18%) (P < .001). A multivariate analysis revealed that a Ki-67 marker ≥ 50% was the only independent predictive factor of pCR (P = .003; odds ratio [OR], 0.133; 95% confidence interval [CI], 0.036-0.5). The median follow-up was 32 months (range, 14-48 months). Patients who achieved a pCR had significantly lower recurrence (P = .001) and higher overall survival (OS) (P = .013) compared with those who did not. There were no statistically significant differences in disease-free survival (DFS) and OS in relation to HRs, the Ki-67 marker as a continuous or categorical variable, and histologic subgroups. CONCLUSION: Proliferation determined by Ki-67 expression ≥ 50% was an independent predictive factor for pCR in patients with HER2(+) BC treated with trastuzumab-based chemotherapy.

The role of immunohistochemistry in breast cancer patients treated with neoadjuvant chemotherapy: an old tool with an enduring prognostic value.

BACKGROUND: To assess the molecular subtypes determined by hormonal receptors (HR) and human epidermal growth factor receptor 2 (HER2) status and the role of proliferation measured by the Ki-67 marker as predictive and prognostic factors in breast cancer patients treated with neoadjuvant chemotherapy. METHODS: A total of 127 breast cancer patients were treated with neoadjuvant chemotherapy every 2 weeks as part of 2 studies. Study A consisted of the administration of Adriamycin (40 mg/m(2)) on day 1 plus paclitaxel (150 mg/m(2)) and gemcitabine 2000 mg/m(2)) on day 2 for 6 cycles (n = 54). Study B consisted of the administration of epirubicin (90 mg/m(2)), cyclophosphamide (600 mg/m(2)) on day 1 for 3 cycles, followed by the administration of paclitaxel (150 mg/m(2)) and gemcitabine 2500 (mg/m(2)) on day 1 with or without trastuzumab according to HER2 status (n = 73). In study A, patients did not receive trastuzumab regardless of HER2 status. The molecular subtypes of the patients with breast cancer were classified as 49% HR(+)/HER2(-), 17.5% HR(+)/HER2(+), 13.5% HR(-)/HER2(+), and 20% HR(-)/HER2(-). RESULTS: Pathologic complete response (pCR), defined as the absence of invasive cells in the breast and the lymph nodes, was achieved in 35 (28%) patients. The pCR rate was significantly different between the molecular subtypes of breast cancer, with 9% in HR(+)/HER2(-), 23% in HR(+)/HER2(+), 50% in HR(-)/HER2(+), and 56% in HR(-)/HER2(-) tumors (P < .001). The pCR rate was significantly higher in tumors that had high Ki-67 (≥20%) expression and were HR(-). HER2(+) was associated with a higher trend of pCR but did not reach statistical significance. The median follow-up was 81 months (r = 15-150 months). Patients who achieved a pCR had a significantly lower recurrence (P = .01) and higher overall survival (P = .02) compared with those who did not achieve pCR. A multivariate analysis revealed that pCR (hazard ratio 0.24 [95% CI, 0.07-0.7]; P = .019), the molecular subtype (hazard ratio 0.3 [95% CI, 0.1-0.8]; P = .02), and the Ki-67 index (hazard ratio 3.2 [95% CI, 1.4-7.1]; P = .004) were significant independent predictors of disease-free survival. Similar results were obtained for overall survival, in which the pCR rate (hazard ratio 0.119 [95% CI, 0.028-0.5]; P = .004), the molecular subtype (hazard ratio 0.17 [95% CI, 0.03-0.86]; P = .02), and the Ki-67 index (hazard ratio 3.6 [95% CI, 1.3-9.7]; P = .01) also displayed a significant influence on survival. CONCLUSIONS: Molecular subtypes and Ki-67 index were independent prognostic factors for disease-free survival and overall survival in breast cancer patients treated with neoadjuvant chemotherapy. A high rate of Ki-67 and HR(-) expression were predictors of pCR.