BackgroundRisk factors for B-cell non-Hodgkin lymphoma (B-NHL) have not been assessed among Palestinian Arabs (PA) and Israeli Jews (IJ).MethodsIn a case-control study we investigated self-reported medical and lifestyle exposures, reporting odds ratios (ORs) and 95% confidence intervals [CIs], by ethnicity, for overall B-NHL and subtypes.ResultsWe recruited 823 cases and 808 healthy controls. Among 307 PA/516 IJ B-NHL cases (mean age at diagnosis = 51 [±17] versus 60 [±15] years, respectively) subtype distributions differed, with diffuse large B-cell lymphoma (DLBCL) being prominent among PA (71%) compared to IJ (41%); follicular lymphoma (FL), was observed in 14% versus 28%, and marginal zone lymphoma, in 2% versus 14%, respectively. Overall B-NHL in both populations was associated with recreational sun exposure OR = 1.43 [CI:1.07–1.91], black hair-dye use OR = 1.70 [CI:1.00–2.87], hospitalization for infection OR = 1.68 [CI:1.34–2.11], and first-degree relative with hematopoietic cancer, OR = 1.69 [CI:1.16–2.48]. An inverse association was noted with alcohol use, OR = 0.46 [CI:0.34–0.62]. Subtype-specific exposures included smoking (FL, OR = 1.46 [CI:1.01–2.11]) and >monthly indoor pesticide use (DLBCL, OR = 2.01 [CI:1.35–3.00]). Associations observed for overall B-NHL in PA only included: gardening OR = 1.93 [CI:1.39–2.70]; history of herpes, mononucleosis, rubella, blood transfusion (OR>2.5, P<0.01 for all); while for IJ risk factors included growing fruits and vegetables, OR = 1.87 [CI:1.11–3.15]; and self-reported autoimmune diseases, OR = 1.99 [CI:1.34–2.95].ConclusionsIn these geographically proximate populations we found some unique risk factors for B-NHL. Heterogeneity in the observed associations by ethnicity could reflect differences in lifestyle, medical systems, and reporting patterns, while variations by histology infer specific etiologic factors for lymphoma subtypes.

e16186 Background: Nivolumab, an immune checkpoint inhibitor, has improved the outcomes of patients with hepatocellular carcinoma (HCC). It is approved for HCC patients previously treated with sorafenib. Outcomes have been reported in previous studies, in malignancies other than HCC, to be worse when patients have been exposed to antibiotics while receiving immune checkpoint inhibitors. We aimed to evaluate the effects of antibiotics on survival in HCC patients treated with nivolumab. Methods: We performed a retrospective review of 59 patients with advanced HCC that have been treated with nivolumab in two academic centers in Saudi Arabia. Patient characteristics, tumor data, antibiotic use (2 weeks prior, during, and 4 weeks after nivolumab therapy), survival data, and other factors were collected. Log-rank test analysis was performed to test the difference in overall survival (OS) time with and without antibiotics use. Results: The majority of patients were males (n=51, 85%), and 38 were Child-Pugh A (64%). A large number of patients had Barcelona Clinic Liver Cancer (BCLC) stage C tumors (n=42, 71%), and 20 patients (34%) used antibiotics. Most patients received nivolumab as second-line therapy after exposure to sorafenib (n=49, 83%). In patients who received nivolumab as first- or second-line therapy (n=57) and did not receive antibiotics, the median OS was double that of patients who received antibiotics (10 vs. 4.5 months, P=0.04). In child A patients who received nivolumab as second-line therapy (n=32), those who were exposed to antibiotics had a statistically significant shorter median OS compared to those who did not (5.5 vs. 20 months, P=0.04). More patients achieved partial response, or complete response (as per modified RECIST criteria) in the cohort that did not receive antibiotics compared to patients who received antibiotics (21% vs. 15%) but that was not statistically significant (P=0.6). Conclusions: This study shows that HCC patients receiving nivolumab have worse survival if they received antibiotics. Antibiotic mediated alteration of the gut microbiome may impact nivolumab response and shorten patient survival. Although this finding may warrant a prospective larger study but it is consistent with other previous studies. Antibiotics should be used very cautiously when treatment with checkpoint inhibitors is considered.

Background Colorectal cancer (CRC) is the most diagnosed cancer among males and third among females in Saudi Arabia, with up to two-third diagnosed at advanced stage. The objective of our study was to estimate CRC survival and determine prognostic factors. Methods Ministry of National Guard- Health Affairs (MNG-HA) registry data was utilized to identify patients diagnosed with CRC between 2009 and 2017. Cases were followed until December 30th, 2017 to assess their one-, three-, and five-year CRC-specific survivals. Kaplan-Meier method and Cox proportional hazard models were used to assess survival from CRC. Results A total of 1012 CRC patients were diagnosed during 2009–2017. Nearly, one-fourth of the patients presented with rectal tumor, 42.89% with left colon and 33.41% of the cases were diagnosed at distant metastasis stage. The overall one-, three-, and five-year survival were 83, 65 and 52.0%, respectively. The five-year survival was 79.85% for localized stage, 63.25% for regional stage and 20.31% for distant metastasis. Multivariate analyses showed that age, diagnosis period, stage, nationality, basis of diagnosis, morphology and location of tumor were associated with survival. Conclusions Findings reveal poor survival compared to Surveillance, Epidemiology, and End Results (SEER) population. Diagnoses at late stage and no surgical and/or perioperative chemotherapy were associated with increased risk of death. Population-based screening in this population should be considered.

Background: In Saudi Arabia, there is no population-based colorectal cancer (CRC) screening, and more than two-thirds of patients are diagnosed with a late stage. We assessed the association between sex and distant metastasis CRC and hypothesize that females, younger age, non-married, and patients with colon cancer would present with metastatic tumors. Patients and Methods: The retrospective cohort study used data from the Ministry of National Guard Cancer Registry. Logistic regression was used to assess the association between sex and metastatic CRC adjusting for patient covariates. In a sensitivity analysis, the association between sex and late-stage CRC was evaluated. Results: A total of 1016 CRC patients met the eligibility criteria, with 37.59% of females and 30.26% of males diagnosed with metastatic CRC. After adjusting for marital status, grade, and morphology, females were 20% more likely than males to present with a metastatic tumor 1.20 (95% CI, 1.04-1.38). Conclusion: Although the entire Saudi population would benefit from CRC screening, women may benefit the most from targeted screening.

Background and Objective: Cancer survival has improved significantly, which reflects the achievements in screening, diagnosis, and treatment. As a consequence, multiple primary malignancies are diagnosed more frequently, with an incidence ranging from 0.52–11.7%. The types of malignancy that coexist and survival patterns vary notably in different countries and geographical areas. Due to the limited literature in Saudi Arabia, a baseline of prevalent malignancy combinations and their survival patterns would support early detection and disease management. Method: This was a retrospective descriptive study conducted from 1993–2022 at King Abdulaziz Medical City, Department of Medical Oncology, Riyadh, Saudi Arabia. Patients with at least two biopsy-proven solid malignancies were included. Patients with hematological malignancies, missing data, or an uncertain or indecisive pathology report were excluded. Result: In total, 321 patients were analyzed. More than half (57.3%) of the patients were female. A third (33%) of the cases were synchronous, and 67% were metachronous. The most frequent site of the first primary malignancy was breast cancer, followed by colorectal, skin, and thyroid cancers. The most frequent site of the second primary malignancy was colorectal cancer, followed by thyroid, breast, and liver cancers. Only 4% of the cases had a third primary malignancy, with colorectal and appendiceal cancers being the most frequent. The most frequently observed histopathology in the synchronous and metachronous malignancies was adenocarcinoma. Breast–colorectal, breast–thyroid, and kidney–colorectal were the most frequently observed malignancy combinations. Conclusion: The current study offers a baseline of multiple primary malignancies in Saudi Arabia and provides supporting evidence that the pattern of multiple primary malignancies varies among different countries and ethnicities. The possibility of developing another primary malignancy should be considered when treating and monitoring cancer patients.

Malignant peritoneal mesothelioma (MPM) is a rare malignancy, presenting with non‐specific and potentially‐misleading manifestations. It represents a diagnostic pitfall as it mimics ovarian carcinoma. Maintaining a low diagnostic threshold, obtaining a detailed history, and utilizing immunohistochemical markers to diagnose MPM is crucial as early diagnosis and treatment might improve survival.

Background: Venous thromboembolism (VTE) represents a considerable burden on cancer patients' survival and quality of life, but this burden varies based on the patient's baseline characteristics and cancer-related factors. Although solid evidence on the predictors and effect of VTE in cancer patients exists.Aim: To evaluate VTE rate, morbidity, and mortality to develop parameters that could predict VTEs and their associated mortality in patients with multiple primary malignancies (MPMs). Method and Results:This was a retrospective cohort study that took place at King Abdulaziz Medical City, Riyadh, Kingdom of Saudi Arabia. Two hundred and forty-two patients with at least two biopsy-proven malignancies and had at least 3 months of follow-up after MPMs diagnosis were included. VTE was diagnosed in 14.5% of the cases, two-thirds of which were deep vein thrombosis. VTE was significantly associated with a higher mortality and worse survival. Predictors of VTE after MPMs diagnosis were a high ECOG performance status at MPMs diagnosis, a metastatic first primary malignancy, and ICU admission after MPMs diagnosis. Having a GI or hematological malignancy as the second primary malignancy, a high D-dimer at ICU admission, and palliative care referral were significantly associated with a higher mortality in patients who had VTE.Conclusion: VTE was diagnosed in 14.5% of patients with MPMs and it significantly compromises their survival. We believe that these results might be of particular benefit since the phenomenon of MPMs is becoming more frequently encountered.

Introduction: Molecular Tumor Boards (MTB) are essential in Precision Oncology Programs. Gaps, however, remain in interpreting comprehensive genomic profiling (CGP) results, and determining their actionability. Our MTB, established in October 2020 and conducted at a tertiary cancer center in Saudi Arabia, focused on discussing patients with complex CGP results and recommending genomic based therapies. Meetings occurred virtually, every month, with oncologists, pathologists and genomicists attending. Methods: This is a retrospective cohort study of patients discussed in our MTB from October 2020 till October 2022. We report the outcomes of these patients who had progressive disease on standard of care (SOC) therapies, and have had non Tier 1 alterations (ESCAT classification) in their CGP reports. We chose an FDA approved, commercially available CGP, which tests 324 genes (FoundationOne CDX). We present the demographics, clinical characteristics, CGP results, recommendations of the MTB, and patient outcomes. Results: Sixty patients fitting the criteria above have been discussed. Median number of prior systemic therapy lines was 2 (range 0-8). The most common primary diagnosis was soft tissue sarcoma (25%), followed by liver and pancreato-biliary cancers (20%), followed by head and neck cancers (15%) and skin cancers (8%). Of the 60 patients, 48 patients had response evaluations. Thirty five patients (out of 48, 73%) have had recommendations for genomic based therapies based on their CGP results. Only 16 patients (out of 35, 46%) received MTB recommended therapies. Eight patients (out of 16, 50%) have remained progression free and on MTB recommended genomic therapy for 6 months and above. The commonest reasons for not receiving MTB recommended therapy were patient clinical deterioration or death (9 patients, 47%) followed by patients responding on current line of therapy (7 patients, 37%). Most common pathogenic targetable alterations were CDKN2A/B mutations (6 patients), followed by alterations in FGFR (5 patients), PTEN (4 patients), BRAF (4 patients), PIK3CA (2 patients) and ERBB2 (2 patients) followed by others (will be presented). Conclusion: Following recommendations, of the first MTB in Saudi Arabia, resulted in improved outcomes of cancer patients who had progressive disease on SOC therapies. Consideration of performing CGP and discussing patients early in their cancer journey may allow them to receive, and benefit from recommended genomic therapies earlier. Citation Format: Kanan Alshammari, Fouad Sabatin, Mehlika Hazar-Rethinam, Faizah Alotaibi, Reham Ajina, Hussam Shehata, Mohammad Alkhayyat, Abdullah Alsaleh, Mohammed Algarni. Outcomes of molecular tumor board recommendations for cancer patients with progression on standard of care therapies in Saudi Arabia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 938.