RESUMO
Triple-negative breast cancer (TNBC) is typically treated with chemotherapeutic agents, including carboplatin (Cb), an DNA platinating agent. The O6-methylguanine-DNA-methyltransferase gene (MGMT) encodes for the protein O6-alkylguanine-DNA-alkyltransferase (MGMT protein). MGMT protein is involved in DNA repair mechanisms to remove mutagenic and cytotoxic adducts from O6-guanine in DNA. In glioblastoma multiforme, MGMT methylation status is a predictive biomarker for increased response to temozolomide therapy. It has been suggested, that MGMT protein may have relevance for cellular adaptation and could have an influence on resistance to carboplatin therapy. We investigated the influence of MGMT promoter methylation on pathologic complete response and survival of patients with TNBC treated in the neoadjuvant GeparSixto trial. In 174 of 210 available TNBC tumors a valid MGMT promoter methylation status was determined by pyrosequencing of 5 CpG islands. In 21.8%, we detected a mean MGMT promoter methylation >10%. Overall, MGMT promoter methylation was not significantly associated with pathological complete response (pCR) rate. After stratification for the two therapy arms with and without Cb no statistically significant differences in therapy response rates between the two MGMT promoter methylation groups could be observed. Our results show that different MGMT promoter methylation status is not related to different chemotherapy response rates in the TNBC setting in GeparSixto.
Assuntos
Ensaios Clínicos como Assunto , Ensaios Clínicos Fase II como Assunto , Metilação de DNA , Metilases de Modificação do DNA/genética , Enzimas Reparadoras do DNA/genética , Regiões Promotoras Genéticas/genética , Análise de Sequência de DNA , Neoplasias de Mama Triplo Negativas/genética , Proteínas Supressoras de Tumor/genética , Biópsia , Estudos de Coortes , Ilhas de CpG/genética , Humanos , Estudos Retrospectivos , Análise de Sobrevida , Neoplasias de Mama Triplo Negativas/patologiaRESUMO
Purpose@#PIK3CA, encoding for subunit p110a of phosphatidylinositol 3 kinase, is frequently mutated in breast cancer. PIK3CAmutation was predictive for pathological complete response (pCR) in human epidermal growth factor 2 positive breast cancer. This study explores the association of PIK3CA mutation and pCR in triple-negative breast cancer (TNBC) treated with neoadjuvant chemotherapy. @*Materials and Methods@#A total of 92 patients with TNBC derived from a prospectively randomized phase II trial GeparSixto study (NCT01426880). Exon 9 and exon 20 of PIK3CA mutations were evaluated by using classical Sanger method with formalin-fixed paraffin-embedded tumor tissues. @*Results@#Seven of 90 tumors (7.8%) were detectable with a PIK3CA H1047R mutation. Overall, PIK3CA H1047R mutation was significantly associated with a lower pCR rate (14.3% vs. 56.6%; odds ratio, 0.128; 95% confidence interval [CI], 0.015 to 1.108; p=0.047). In carboplatin- containing treatment patients, H1047R mutation trended to predict a lower pCR rate (20% vs. 62.5%; p=0.146). In a multivariable analysis, H1047R mutation trended to predict a lower pCR rate (hazard ratio, 0.1; 95% CI, 0.01 to 1; p=0.056). @*Conclusion@#TNBC with a PIK3CA H1047R mutation was less likely to achieve pCR after anthracyclinebased neoadjuvant chemotherapy. Development of H1047R mutant selective inhibitors might be helpful to conquer this subtype of breast cancer.
