665 Background: Bevacizumab, a humanized antibody against the molecular target endotelial growth factor VEGF-A, has incorporated to the standard of care of metastatic colon-rectal cancer (mCRC). A recent study has suggested that the left colon localization of the primary tumor may be a factor associated with a poorer survival in individuals treated against mCRC with bevacizumab including chemotherapy. Our objective was to analyze the impact of the localization of the primary tumor on the survival of patients with mCRC treated with bevacizumab. Methods: Prospective cohort study conducted in a tertiary-care hospital in Spain. Twenty-nine consecutive patients with mCRC who started a first-line therapy including bevacizumab were included. Patients were followed up until death, lost to follow-up or the censoring date (31th August, 2013). The primary end-point of the study was death from any cause. Predictors of survival, including the localization of the primary tumor, were assessed. Results: The median (Q1-Q3) age was 59 (52-67) years and 13 (45%) patients were male. Chemotherapy scheme was XELOX in 13 (45%) patients, FOLFOX in 8 (28%), FOLFIRI in 5 (17%), XELIRI in 2 (7%) and capecitabine in 1 (3%) patient. The localization of the primary tumor were distributed as follows: rectum in 6 (21%), sigmoid colon in 9 (31%), left colon in 9 (31%) and right colon in 5 (17%) patients. After a median (Q1-Q3) follow-up of 29 (13-41) months, 19 (66%) patients died. There were no patients lost to the follow-up. The mean (SD) survival in patients with left colon cancer was 25 (8) months whereas it was 47 (7) months in the remaining population (p = 0.1). The low sample size precluded to perform reliable multivariate analyses. Conclusions: Our study suggests that left colon localization of the primary tumor may have a worse prognosis in patients with mCRC treated with bevacizumab. Although no statistically significant differences have been observed, this fact may have been a consequence of the limited power of the analysed sample. Collaborative studies should be perfomed in order to clarify this issue.

with NAST. On CNB samples stained with haematoxylin-eosin, we performed a TIL density assessment, expressed as the percentage of area of intratumoral stroma covered by lymphocytes (as per International TIL Working Group recommendations in 2014). pCR was defined as complete remission in breast and in axillary nodes. We used univariate linear regression to calculate the above noted correlation values. We also determined the optimal TIL cutoff value, which showed the best differentiation between the two outcome groups when used to segregate our patients into low TIL and high TIL subgroups. For that, we performed a chi-square test using TIL cutoff values from 0 to 100 in increments of 1.Results: We enrolled 141 patients. Our patient population consisted of: 18 her2+ (89% pCR), 2 luminal A (no pCR), 65 luminal B (11% pCR), 35 triple-(51% pCR) and 21 triple+ (43% pCR). The TIL values in pCR and no-pCR groups were shown to be statistically significantly different, with a p-value of <0.001 and a standard error of 0.0017. The distribution of TIL values in the two groups was: mean and stdev 28.12(AE26.15), median 20 for the pCR group, and mean and stdev 10.33(AE15.12), median 5 for the no-pCR group. The optimal TIL cutoff value in our patients was 10 (p 0.00003).Conclusions: Our results show that higher TIL scores correlate with higher pCR outcomes, which is congruent to the results thus far observed in the available literature. This also hints at our TIL scoring quality being good.

e11075 Background: Overexpression HER 2 + + + is a distinct group within the breast cancer with different treatments in both the adjuvant and advanced setting. However, from the clinical point of view, there are significant differences within this group HER2 + + + referred to response to trastuzumab, metastatic sites and survival intervals. Recently reported data guides to a worse prognosis in the subgroup expressing hormone receptors. We propose to study these differences in HER2 + + + between subgroups hormone receptor positive and negative. Methods: Retrospective observational study of all patients diagnosed with HER2 + + + at the Hospital Virgen de Valme between the years 2005-2011. We studied the disease-free interval (DFS) and global survival (OS). We also studied the frequency of brain metastases and cerebral disease-free interval (BDFS). We explore differences between the hormone receptor-negative groups (group A) and positive (group B). All patients have been treated with at least one line of trastuzumab. Results: N = 73 (40 group A and 33 group B). Median age was 58 and 55 respectively. 33 patients had metastases in the course of the disease. 7 patients initially diagnosed with metastatic stage. There is a difference of 5.0 months in group A favorable DFS (p = 0.28). The OS was 52 months in group A versus 48 months in group B (difference of 4 months p = 0.18). The BDFS was 57 months for group A and 15 months for group B (p = 0.1). The incidence of brain metastases was 27% versus 9%. Conclusions: Our data suggests a better prognosis in terms of DFS, OS and BDFS in hormone receptor-negative group. Likewise, the incidence of brain metastases was three times lower. We need well design clinical trials, monitoring and therapeutic strategies for this subgroup of patients.

e12612 Background: Double anti-Her2 blockade combined with chemotherapy (CT) is a standard regimen in Her2 positive locally advanced breast cancer (LABC) with a high risk of relapse. TCHP provides more anti-Her2 treatment, better pathological complete response (pCR) rates and less cardiotoxicity. However, it is not a very widespread option due to the risk of toxicity. Our group shows a manageable toxicity profile by adding G-CSF as primary prohylaxis. Methods: We describe our experience with neoadjuvant TCHP and pegfilgrastim combination between years 2017-2023. Efficacy and safety were analyzed and compared with other schemes accepted by clinical guidelines. Results: 62 patients, median age 48 years; 61.3% were premenopausal; 54.8% were stage II at diagnosis and 45.2% were stage III; 67.7% had N+; 62.9% had RH-. A total of six cycles were completed in 85.5%; 8 patients discontinued treatment due to toxicity. The most frequent adverse events were hematological (grade 3-4 in 8.1%) and digestive (grade 3-4 in 19.4%). No cardiac event was reported. 6.5% were hospitalized due to toxicity (3.2% febrile neutropenia). Dose reduction was needed in 43.5%. Clinical response occurred in 98.4% and radiological response in 87.1% (complete in 38.7%). pCR (ypT0/isN0) was obtained in 67.7% (66.7% in N+; 77.4% in RH-). Up to now, 4 patients have relapsed (3 of them had pRC) and 3 have died. After median 24.5 months of follow-up, the median relapse-free and overall survival by Kapplan-Meier have not been reached. Cox regression shows that getting rPC does not impact survival. The Odds Ratio shows a higher proportion of obtaining pRC in the RH- and N+ subgroups, but without statistically significant differences. Conclusions: Our data based on combination of TCHP and pegfilgrastim shows considerable efficacy with an acceptable toxicity profile. The main advantage is the intensification of double lock dose, without anti Her2 window period, avoiding the addition of anthracyclines and, therefore, cardiac toxicity. pRC and toxicity profile results were better than other regimen proposed in other studies. Our data shows that pRC has no impact on survival. We assume a favorable association between pRC and N+ and HR-, although not statistically significant, probably due to the small amount of patients. Based on these favorable results, we believe that the priority use of TCHP-GCSF should be considered in the neoadjuvant treatment of Her2+ LABC. [Table: see text]

e13073 Background: Cyclin kinase inhibitors (CDKi) are the standard of care in the first line of luminal (Lum) metastatic breast cancer (MBC). HER2 overexpression is a classic risk factor in BC, however, the use of targeted therapy has changed the prognosis of this disease, even with anti-HER2 efficacy data in cases of low HER2 expression. We wonder if the level of HER2 expression can be a predictor of efficacy in treatment with CDKi. Methods: Descriptive, observational, retrospective and analytical study of patients with MBC treated with CDKi, in the period 2018-2022. Descriptive and analytical statistical analysis (IBM SPSS Statistics 22) using logistic regression and Kaplan-Meier with long-rank test to analyze the relationship between CKi efficacy and HER2 expression (negative = 0+; HER2 low = 1+ and 2 + with SISH negative). Results: We analyzed 152 patients (p) with Lum MBC under treatment with CDKi (median 58 years), in first and successive lines. HER2 expression: 31% 46p (0+), 54% 81p (1+) and 14% 21p (2+ and SISH negative). 41% were treated with palbociclib, 34% with ribociclib, and 26% with abemaciclib. Radiological response (RR) to CDKi was achieved by 34.1% (CRR 2.4%, PRR 31.7), and the rest stable disease (SD) or progressive disease (PD): SD 42% and PD 22%. In the overall OR, there was no evidence of a risk association between the response to CDKi and the level of HER2 expression. We obtained similar results in the analysis stratified by type of CDKi. In the multivariate study, for the variables CDKi type and HER2 expression, the logistic regression model was not statistically significant either. Regarding the Kaplan-Meier analysis, we compared the median PFS and OS using the Long-rank test, based on the expression of HER2. In the complete series we did not find statistically significant differences between the curves. In the palbociclib subgroup the curves split in favor of HER2 0+ vs. HER2 low: 44 months 95%CI (7.6-80) vs 16 months 95%CI (7.9-24); p = 0.01. Regarding OS, we found no significant differences. With ribociclib, the curves separate in favor of HER2 low versus HER2 0+: 33 months 95%CI (7.2-18) vs. 13 months 95%CI (23-42); p = 0.03. In OS we did not find significant differences either. In the subgroup with abemaciclib, we observed a trend towards greater survival in HER2 0+ patients, but with no significant difference between the PFS or OS curves. Conclusions: Based on our study, the expression of HER2 could be considered a predictor of efficacy depending on the CDKi used. We assume greater survival with palbociclib in HER2 negative patients (0+) and with ribociclib in HER2 low patients. We consider it essential to develop studies with a larger sample size and clinical trials that allow us to demonstrate the hypothesis of our work with scientific evidence.