Breast cancer is the most frequent cancer in women and is prognostically very heterogeneous. Early breast cancer has an excellent overall prognosis with long-term survival above 90%. In this group we can also find patients with highly unfavourable progress with a risk of future disease relapse. Due to effective anticancer treatment is a main task of precise clinical decision to determine risk of an individual patient in the term of cancer relapse. We can use clinical (tumor diameter, lymph nodes) and pathological markers (grade, ER, PgR, HER2, and Ki-67), all of them have low individual sensitivity and specificity. Molecular tests based on multigene DNA or RNA assays have higher sensitivity and specificity but their interrelated concordance is low. One of the main scientific task is to find almost specific and sensitive prognostic biomarkers. microRNAs are small, highly stable, non-coding RNAs, which regulate tens of mRNAs and proteins inside cells. In cancerogenesis, they could act as oncogenes or tumor supressors as well and affect main steps of initiation and progression of cancer. One of the scientific directions is to determine their prognostic significance. Many experimental and clinical studies defining prognostic significance of miRs in early breast cancer was published but their data were...

Introducción: El cáncer de mama es más frecuente en mujeres y la segunda con mayor tasa de mortalidad en el Perú a pesar de la existencia de avanzadas técnicas oncológicas. Por ello, planteamos comparar la Radioterapia Externa (RE) con la Radioterapia intraoperatoria (RIO) en el tratamiento temprano. Esta última, técnica de concentración de dosis, cuenta con poca experiencia a nivel nacional. Objetivos: Comparar supervivencia global y libre de enfermedad a los 2 años, la incidencia de recurrencia local ipsilateral y toxicidad en pacientes con cáncer de mama temprano, que fueron sometidas a RIO o RE durante los años 2016-2018 en una clínica privada oncológica. Materiales y Métodos: Se realizó un estudio observacional, analítico de cohortes retrospectivo, con análisis bivariado para las variables dependientes; recurrencia local ipsilateral, toxicidad y sobrevida con las variables independientes. La diferencia entre estos grupos fue analizada con el modelo multivariado de regresión tipo Cox, para obtener el Hazard Ratio. El análisis de supervivencia se calculó mediante el método Kaplan-Meier, y la diferencia fue sometida a prueba log rank. Resultados: De un total de 482 pacientes con cáncer de mama temprano; 166 recibieron RIO y 316 recibieron RE convencional, con una mediana de seguimiento de 54 meses (RIC 27,1-63,4). La SG fue de 96,47% a los 2 años (98,8% RIO vs 95,25% RE), el análisis multivariado no mostró diferencia significativa. La SLE fue de 98,27% (97,97% RIO vs 98,73% RE). La recurrencia local ipsilateral de RE no fue inferior al de RIO y la toxicidad reportada como radiodermitis aguda fue mayor en el grupo que recibió RE (p<0,05). Discusión: Nuestro estudio es el primero en Perú que sugiere que dar RIO es al menos tan efectivo y con menor efecto colateral que la RE convencional. / Introduction: Breast cancer is more frequent in women and the second with the highest mortality rate in Peru despite the existence of advanced oncological techniques. For this reason, we propose to compare External Radiotherapy (EBRT) with intraoperative Radiotherapy (IORT) in early treatment. The IORT uses a dose concetration, has little experience at the national level. Objectives: To compare the global and disease-free survival at 2 years, the incidence of ipsilateral local recurrence and toxicity in patients with early breast cancer, who underwent conventional IORT or EBRT to conservation surgery during the years 2016-2018 in a private cancer clinic. Materials and Methods: An observational, analytical, retrospective cohort study was carried out, with bivariate analysis for the dependent variables; Ipsilateral local recurrence, toxicity and survival with the independent variables. The difference between these groups was analyzed with the Cox-type multivariate regression model to obtain the Hazard Ratio. Survival analysis was calculated using the Kaplan-Meier method and the difference was subjected to a log rank test. Results: From a total of 482 patients with early breast cancer; 166 received IORT and 316 received conventional EBRT, with a median follow-up of 54 months (IQR 27,1-63,4). SG was 96.47% at 2 years (98,8% RIO vs 95,25% RE), the multivariate analysis did not show a significant difference. The DFS was 98,27% (97,97% RIO vs 98,73% RE), a significant difference according to multivariate analysis (HRa 6,44 CI95% 1,46-28-29). The ipsilateral local recurrence of EBRT was not inferior to that of IORT and the toxicity reported as acute radiodermatitis was higher in the group that received EBRT (p <0,05) Discussion: Our study is the first in Peru to suggest that administering IORT is at least as effective and with fewer side effects than conventional EBRT. / Tesis