e12574 Background: Currently there are no primary cultures or cell lines derived from patients with breast cancer and obesity. It has been postulated that breast cancer in obese women behaves differently as it does in non-obese women, as is composed of distinct biological features, as was generated in a different metabolic environment, as well as pertains to a different prognosis and different response to chemotherapy, lower rates of overall survival and a greater probability of recurrence. By creating a primary breast cancer culture bank of breast cancer tumors from women with obesity (BMI > 30kg/m2), we will establish a cell line exclusive to obese women in Mexico, where targeted therapy may be tested and treatment may be individualized depending on the characteristics of the patient. Methods: This study recruited 32 women with breast cancer and a BMI > 30 kg/m2, matched by 6 controls with are non-obese women with breast cancer. Elegibility criteria was determined by women with breast cancer confirmed by pathology, who had not been subjected to prior treatment regarding the neoplasm. The breast cancer removing surgeries and the patients were selected from the ABC Medical Center in Mexico City and all procedures were approved by the research and ethics committee of the hospital in question. Results: Through extensive communication a cooperative protocol was established between the departments of surgery, oncology, pathology and nursing to coordinate efforts and be able to take a 2 – 5 mm sample of the breast tumor removed from the patient. To be able to distinguish cancer cells from non-cancer cells (epithelial cells, fibroblasts, adipocytes) the Hayflick limit was be utilized. Once a primary breast cancer culture was established, 12 million cells will be injected into the subscapular area of athymic, nu-nu mice to be able to monitor tumoral growth in vivo and conduct a subsequent cellular analysis, determining it still pertains to the same characteristics of the tumor from which it was obtained. Conclusions: A primary breast cancer culture repository from patients with a BMI > 30 kg/m2 was established. This is the first primary breast cancer culture for both Mexican and obese women with breast cancer, the first in vitro method of analysis of specific characteristics typical of the Mexican population. Translational research may now be conducted on these new tumoral cultures to create individualized therapy for women with the distinct, aforementioned characteristics.

e20565 Background: Malignant pleural mesothelioma (MPM) is a rare and aggressive cancer. Prognosis is generally poor, with a median overall survival (mOS) of approximately 12 months. MPM appears to be directly linked to immunosuppressive mechanisms, leading to use of checkpoint inhibitors for patients with this disease. Methods: We performed a retrospective chart review of patients with MPM at our institution between January 2015 to December 2020. All patients were over 18 years at the time of diagnosis of mesothelioma, a total of 8 patients were retrieved from the pathology database of The American British Cowdray Medical Center. The clinical-pathologic features collected were sex, age, performance status, risk factors, pTNM stage (AJCC 8th edition), histology type, sintomatology of onset, metastases sites and treatment. Clinical response rate and other outcomes were assessed. Descriptive statistics were used to describe a patient's demographic and disease characteristics. Results: 8 patients, aged 49 to 71 years (median of 65) at diagnosis of MPM were treated in our center. Both sex presented 4 patients in total. An identifiable risk factor was recorded in 4 patients (2 with asbesto exposure and 2 with heavy smoking). 7 patients (87.5%) had PS 0 or 1, the remaining has PS 2. The clinical stage at diagnosis was unresectable in 7 patients. 3 patients were assessed with PD-L1 expression (SP263 or 22C3), only one with expression of 20%. All patients received at least one scheme of chemotherapy prior to receiving immunotherapy, 25% received bevacizumab/platinum/anti-folate agents. Checkpoint inhibitors were introduced as a second line in 20% and in 80% has a third or more lines. Pembrolizumab was used in 20% and Nivolumab in 80%. The tumor responses with immunotherapy were as follows: partial response 12.5%, stable disease 75% and progressive disease 12.5%. Median progression-free survival of the first line treatment was 18.9 months (4.6-33.6 months), and for the line with checkpoint inhibitors was 11.2 weeks (7-21.2). In the full cohort, mOS was 37.0 months (95% CI:14.5-39.6). According to histology, the mOS for epithelioid-type was 36.6 months and for biphasic-type was 14.6 months (p = 0.42). mOS was 37.0 months for the group with immunotherapy and 15.0 months for those with standard chemotherapy (p = 0.14). The most frequently reported immune mediated adverse events were hypothyroidism and colitis (each one with one patient). Conclusions: In this real-world analysis, mOS was superior to those obtained in the MAPS2 trial (mOS 11.9 months), despite the fact that 80% of the population that received immunotherapy was in third or more lines. Limitations include limited numbers of patients, retrospective review, single institution, and inclusión of many heavily pretreated patients. Also molecular and immunohistochemical results such as PD-L1 status were only available on a limited number of patients.

e16105 Background: Gastric cancer (GC) and gastroesophageal junction cancer (GEJ) are the second most prevalent and lethal digestive malignancies worldwide. According to GLOBOCAN 2020, the incidence in Mexican population is 4.5% and represents 7% of all deaths. In GC and GEJ, the frequency of HER2 overexpression varies widely in the literature. Actually the blocking anti-HER2 is the standard therapy in GC and GEJ with overexpression HER2 according to the ToGa Trial. There are few studies that describe this population in mexican patients. Methods: We conducted a retrospective, observational analysis. Medical records of patients with GC or GEJ cancer from January 2015 to January 2021 were reviewed. A total of 91 patients were retrieved from the pathology database. Clinicalpathologic features collected were sex, age, pTNM stage (AJCC 8th edition), histology type, HER-2 status, metastases sites and treatment. The HER-2 determination was performed in all cases with immunohistochemistry (IHQ). Results: We found 10 patients with GC and GEJ with HER-2 overexpression by IHC, five patients with FISH positive and 2 of them with amplification by next generation sequence (FoundationOne). The median age was 56.9 years (27-68). There were more male patients (n = 8) than female patients (n = 2), with male/female ratio of 4:1. 8 patients had performance status (PS) 0 or 1, and the rest PS 2. The primary site was gastric carcinoma in 3 patients, and in 7 the tumor was located in GEJ. The clinical stage at diagnosis in 7 patients was metastatic, and 3 locally advanced. The most common sites of metastasis were lung (n = 5), liver (n = 4), and pleural, bone and central nervous system (each one with one patient). Intestinal-type GCs were most prevalent with 8 patients, and the rest were diffuse and signet ring cells. All patients received anti-HER2 blockade, 6 in the first line therapy, and 4 patients in the second line or more. Regarding the backbone regimen of the trastuzumab based therapy, fluoropyrimidine/platinum were the mainstay in 9 patients, and 1 with platinum and taxane scheme. Median number of cycles of trastuzumab was 8 (range, 4-24). The tumor responses were as follows: complete response (CR) 10%, partial response (PR) 30%, stable disease 50% and progressive disease 1 patient. The median progression-free survival was 6.6 months (1.3-23.1 months), and a median of overall survival was 21 months (6.4-51.5 months). The most frequently reported adverse events were diarrhoea in 3 patients (all grade 2), and mucositis in 1 patient. Cardiac adverse events were not reported. Conclusions: In our cohort, the prevalence of HER2 overexpression by IHC was 11%. In previous reports, the most important ToGa trial, 22% of the patients with metastatic GC and GEJ were HER2 positive. The PFS and OS in ToGa trial were 13.8 and 17.1 months respectively. By comparison our cohort the PFS and OS in ToGa trial were 6.6 and 21 months.

e22517 Background: there are few reported series n women with breast cancer (BC) and COVID-19, a better prognosis has been observed, with a lower rate of hospitalization and mortality than other neoplasms. Methods: We conducted a restrospective, non-experimental, observational, single center, study with a sample of 69 patients with BC who had presented COVID-19, in the period between March 2020 to August 2021. Clinicopathological characteristics of patients with BC were compared between severe and non-severe covid 19 groups, as well as hospitalized and non-hospitalized patients. An analysis of possible risk factors associated with severe disease and hospitalization was performed. Results: 69 cases were reported, median age 52y, mean BMI 25.2, ECOG 0-1: 97%. Smoking history in 24%, diabetes and hypertension were the most frequent comorbidities. The most frequent histology was ductal carcinoma in 80.6%, 73.8% showed ER + and 69.3% PR +, HER2 was overexpressed in 9.2%. The early stages predominated, I 22 (31.3%), II 25 (37.3%), III in 12 (17.9%) and IV in 6 (9%). The most frequents symptoms of COVID-19 were fatigue 70.1%, fever 65.7%, cough 59.7%, headache 56.7%, hyposmia 47.8%, dysgeusia 38.8%. A total of 53 (76.8%) mild cases, 14 (20.3) severe cases and 2 (2.9%) critical cases were registered. The 89.9% (62 patients) were treated as an outpatient basis, while 7 (10.1%) required hospitalization. Active treatment (< 45 days) at the time of COVID-19 was hormonal therapy 36 (50.7%), chemotherapy 11 (16.4%), anti-HER2 in 3 (4.5%), immunotherapy in 1.5%, targeted treatment in 4 (6.0%), surgery in 7 (10.4%) and radiotherapy in 1 (1.5%) patient. When comparing the severe and non-severe groups, as well as hospitalized versus non-hospitalized, we observed no difference between the clinicopathological characteristics. Then, we serch for possible risk factors, in wich, surgery in a period of less than 3 months increases the risk of severity OR 1,297 (95% CI 1,112-1,514), the risk of hospitalization increased in the triple negative subgroup OR 1,143 (95% CI, 1,035- 1,262), surgery less than 3 months OR 1,116 (1,014-1,229) and chemotherapy less than 45 days OR 1,217 (95% CI, 1,024-1,447). Conclusions: In patients with BC, the prevalence of severe or critical COVID-19 was 23% and the hospitalizacion rate 10%. No patient died from this infection. The clinical and pathological characteristics of BC do not appear to increase the risk of severe COVID-19 or the rate of hospitalization. Surgery performed in a period of less than 3 months is marginally associated with an increased risk of severe disease. Chemotherapy, targeted therapy, and immunotherapy do not modify the risk of severe disease; however, higher Ki 67, triple negative subgroup, surgery and chemotherapy showed a slight increase in risk of hospitalization.

e21522 Background: Immune-related adverse effects (irAE´s) of immune-checkpoint inhibitors (ICIs) have been linked with a better treatment response in melanoma patients, especially cutaneous toxicities. However, little is known regarding other irAE´s which is important as they can be used as clinical markers of an adequate therapeutical response. Methods: We conducted a retrospective study on patients who were diagnosed with melanoma and received treatment with ICI´s between January 2015 until December 2021, immune related adverse events and their relationship with overall survival in melanoma patients treated with ICIs was the main objective of this study. Results: 53 records of patients with advance melanoma treated with ICIs between january 2016 to december 2021, demographic characteristics were as follow: 64.2% were male, mean age at diagnoses was 60.3 years, 41.5% had smoking history and 15.1% were Jewish. At diagnosis 73.6% of patients had a good functional status (ECOG 0-1). The most common histological subtypes were epithelioid (34%), and nodular (22.6%). Lung metastases was the most common affected site (49.1%), followed by brain 43.4% and non-regional nodes 42.5%. BRAF mutations was determined in 81.1% of the biopsies and 36% of them being V600E mutation. ICI´s was the preferred first line treatment in 83% of cases, median number of administered cycles were 6 (range 1-54 cycles), 60.4% of patients received pembrolizumab, 37.7% nivolumab plus ipilimumab, 20.8% nivolumab monotherapy and 5.7% ipilimumab. Throughout the studied period IrAE´s were reported in 34% of patients with 66.7% of them being grade 1-2 and 33.3% grade 3-4. The most common IrAE’s: vitiligo 38.8%, hypothyroidism22% and 3.8% pneumonitis. Median PFS at 12 months and OS was significantly better in the group of patients with irAE´s: Patients who develop an irAE´s are 7 times more likely to be disease free at 12 months and 4.1 times more likely to have a longer OS regardless of severity and type of toxicity. The impact of developing irAEs is significantly important for PFS (HR: 11.9, CI 95%: 3.28-4.71) as median PFS was not yet reached in this group. Conclusions: Development of irAEs is associated with favorable outcomes to ICIs with patients being 7 times more likely to be 12-month disease free and 4.1 times more likely to have a longer OS. irAEs can be used as clinical markers of an adequate treatment response.[Table: see text]