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e14049 Background: Ratios of differential blood counts (hematological indices, HI) had been identified as prognostic variables in various cancers. In primary central nervous system lymphomas (PCNSL), higher baseline neutrophil-lymphocyte ratio (NLR) in particular was found to portend a worse overall survival. However, it was often observed that differential counts shift drastically following steroid administration. Moreover, steroids are an important part of the arsenal against PCNSL due to its potent lymphotoxic effects. We showed that the effect of steroids on differential blood cell counts and HI could be an early biomarker for subsequent progression-free (PFS) and overall survival (OS). Methods: This study retrospectively identified all adult patients who received a brain biopsy from 2008 to 2019 and had histologically confirmed PCNSL, and included only those who received chemoimmunotherapy, with documented use of corticosteroids prior to treatment induction. Different blood cell counts and HI were calculated at three time-points: baseline (pre-steroid), pre-chemoimmunotherapy (post-steroid) and post-chemoimmunotherapy. Tumor progression and survival data were collected and analyzed through Kaplan-Meier estimates and Cox regression. We then utilized selected variables found to be significant on Kaplan-Meier analysis to generate a decision-tree prognostic model, the NNI-NCCS score. Results: A total of 75 patients who received chemoimmunotherapy were included in the final analysis. For NLR, OS was longer with higher pre-chemoimmunotherapy (post-steroid) NLR (dichotomized at NLR≥4.0, HR 0.42, 95% CI: 0.21-0.83, p = 0.01) only. For platelet-lymphocyte ratio (PLR) and lymphocyte-monocyte ratio (LMR), OS was better for lower post-chemoimmunotherapy PLR (dichotomized at PLR≥241, HR 2.27, 95% CI: 1.00 to 5.18, p = 0.05) and lower pre-chemoimmunotherapy (post-steroid) LMR (dichotomized at LMR ≥25.7, HR 2.17, 95% CI: 1.10 to 4.31, p = 0.03) respectively only. Decision-tree model using age ≤70, post-steroid NLR > 4.0, and pre-steroid (baseline) NLR < 2.5 divided patients into three risk categories – low, medium, high – and achieved good accuracy (area-under-curve of 0.78), with good calibration (Brier score: 0.16) for predicting 2-year overall survival. Conclusions: We found that post-steroid NLR, when considered together with baseline NLR, has prognostic value, and incorporation into a prognostic model allowed accurate and well-calibrated stratification into three risk groups.

e23527 Background: Head and neck angiosarcoma (HN-AS) is a distinct entity that commonly arises from the scalp of elderly Asian males. We strive to study the impact of different treatment modalities and explore correlation with blood inflammatory markers. Methods: A prospectively maintained database was queried for patients with biopsy-confirmed HN-AS treated in a single tertiary institution from 2000 to 2018. Results: Eight-eight patients were analyzed. Median age is 73.5 (IQR 66-81.2). Fifty-five (64%) were non-metastatic at diagnosis, seventy-four (84.1%) arose from the scalp and 70.5% were males. Of the 55 non-metastatic patients, 21 received curative surgery and 7 patients received adjuvant radiotherapy. Patients who had curative surgery had smaller tumors (p < 0.001). Local relapses were 57.1% vs 35.7% without and with radiotherapy (p = 0.34). Five patients were still alive at time of analysis but only 1 with a follow up of more than 5 years. In this group, 2-year and 5-year locoregional progression free survival (PFS) were 56.0% and 26.1%, distant PFS were 73.7% and 41.4%, OS were 48.6% and 17.7%. In the group that was metastatic at presentation (n = 31), 17 patients received palliative chemotherapy with 7 patients documented as partial response. 17 patients received palliative radiotherapy with largely good symptomatic relief. Six patients received photodynamic therapy: with 1 documented abscopal response. The median survival is 6.9 months. Overall, 64 patients received palliative chemotherapy and 42 received palliative radiotherapy (in the metastatic or inoperable setting). The most common chemotherapy regimen was single agent paclitaxel (56.3%). In the first line setting, 66.7% experienced at least a partial response to chemotherapy. Comparing the 3 different treatment groups (metastastic vs curative surgery vs non-metastatic/no curative surgery), patient with curative surgery had the best OS (p = 0.007) but worse PFS compared to non-metastatic but no curative surgery patients (p = 0.03). Using full blood count at diagnosis, hazard ratio for neutrophil lymphocyte ratio (NLR) and lymphocyte monocyte ratio (LMR) were 1.02 (p = 0.06) and 0.80 (p = 0.02) respectively for OS. In multivariate analysis, age, stage and LMR were the only 3 significant predictors for OS. Conclusions: Cutaneous HN-AS is an aggressive disease. Although patients who had curative surgery had better overall survival which could be confounded by smaller tumours, and they also had earlier documented relapses possibly due to closer surveillance or tumor growth promotion from post-surgical inflammatory response. The value of adjuvant radiotherapy is unknown. Palliative radiotherapy is useful, and a more hypo-fractionated approach should be favored. Palliative single-agent paclitaxel is effective although overall survival remains grave. Blood inflammatory indicators correlate with survival.

e13629 Background: Cancer in adolescents and young adults (AYAOs) refers to patients diagnosed with a malignancy between 16 and 39 years old. This is thought to be 5% in the Western population. The exact incidence and distribution in Asia is uncertain although the WHO estimated 650 000 AYAs to be newly diagnosed in this part of the world in 2018. There is limited data on the incidence and epidemiology on AYAs in Asia, but it is known from the western literature that the distribution of cancer types, clinico-pathological features and outcomes in this population is very different. We therefore, sought to evaluate the pattern of cancer types among the different age groups of the AYA population seen in a high-volume single Asian tertiary cancer centre. Methods: We undertook a retrospective observational study of all patients diagnosed with cancer between 16 and 39 years old who presented to the National Cancer Centre Singapore (NCCS) from 1 January 2015 to 31 December 2019. Results: A total of 2583 cases was observed during the 5-year period. The male: female ratio was 1:1.75. The majority of the patients were between of 35-39 years (y) ( n= 1128, 44.0%). The most common cancer across the different age groups in females were sarcoma (16-19 y), hematologic malignancies (20-24 y) and breast cancer (25-29 y, 30-34 y and 35-39 y). The most common cancer across the different age groups in males were hematologic malignancies (16-19 y), germ cell tumours (20-24 y), germ cell tumours, hematologic malignancies and sarcoma (25-29 y), hematologic malignancies (30-34 y) and colorectal cancers (35-39 y). The majority of the patients presented were localized disease (38.3%), while 19.4% presented with lymphatic involvement. Amongst 507 (19.6%) patients presenting with metastatic disease, 126 patients have deceased. Conclusions: This population has unique characteristics compared to their geriatric and pediatric counterparts. With an increased incidence and expected longer survivals, more efforts are needed to better understand the clinicopathological features of the AYA population. This will enable us to better survival rates and long-term treatment outcomes.

e16651 Background: Hepatobiliary cancer is one of the common cancers within Asia with 80% of global cases occurring in the continent alone. Currently little is known about the incidence of hepatobiliary cancer in the Adolescent and Young Adults (AYA). In this population, hepatobiliary cancer may present in an insidious manner due to low suspicion and management may result in a higher likelihood of survivors with long-term treatment-related toxicities. We aim to highlight the clinicopathological features and treatment outcomes in this age-group in an Asian high-volume tertiary cancer institution. Methods: Patients diagnosed between the age of 16-39 with hepatobiliary cancers between 1st January 2015 to 31st December 2019 in a single-centre institution in Singapore were included in this study. Results: There was a total of 84 AYA patients with hepatobiliary tumours who were referred to our institution. Median age of diagnosis was 35 years old (n = 84). 32 patients (38.1%) had hepatocellular carcinoma, 22 patients (26.2%) had biliary tract tumours, 11 patients (13.1%) had neuroendocrine cancers while 19 patients (22.6%) had other tumour types (Figure 1). Male incidence was highest in all hepatobiliary AYAs (n = 56, 66.7%, p = 0.002) and hepatocellular carcinomas (n = 25, 78.1%, p = 0.001) (Table). 65 patients (77.4%) remain alive as of 31st December 2019. Conclusions: Patterns of hepatobiliary incidence differ between sexes. In the young AYA population, hepatocellular precursor cells may have sex-specific features affecting malignant potentials. More studies should be done to further elucidate the genomic and epidemiology of hepatobiliary tumours in the younger population of patients to better outcomes in this population. [Table: see text]

e13630 Background: Hematological malignancies is thought to be one of the more common Adolescent and Young Adult (AYA) cancers and constitute leukemias and lymphomas. However, little is known about its incidence and prevalence in Asia. We also do not have any data on its behavior or its prognosticators. The outcomes of this group of patients is also unknown when compared to the pediatrics or geriatrics, but is expected to be not as ideal. There is no consensus on whether this group of patients should be treated as pediatrics or as the older adults. We have sought to evaluate the prevalence and trends in a single large-volume tertiary cancer centre in Asia. Methods: We extracted data on all patients with cancer between 16-39 years old who were seen at our centre (National Cancer Centre Singapore) during the period of 1st January 2015 and 31st December 2019. In total, we had 2583 patients. We then excluded all other cancer types except those with a hematological malignancy and 5 other patients due to incomplete data. Results: There were 319 patients with a hematological malignancy. 153 (48%) were female and 166 were male(52%). Most of the patients presented between 30-39 years old (171, 53.6%). There were 54 (2.1%) leukemias and 265 (83.1%) lymphomas. Of those with leukemias, 46 (85.2%) had acute leukemia and 9 (14.8%) had chronic leukemias. Among the lymphoma patients, there were 194 (73.2%) Non Hodgkin Lymphoma (NHL) patients and 69 (26.0%) Hodgkin Lymphoma (HL) patients. There were 149 (46.7%) B Cell lymphomas and 38 (11.9%) T Cell lymphoma patients. The most common B cell Lymphomas is Diffuse Large B Cell Lymphoma (128, 85.9%) and the most common T Cell Lymphomas is Peripheral T-cell Lymphoma (28, 73.7% patients). Conclusions: AYAs with a hematological malignancy form a significant portion of the cancers we see in this age group. Yet, little information is available with regards to their clinico-pathological characteristics, especially in Asia. Work is underway to further elucidate these differences so that we can better their outcomes.

11047 Background: Angiosarcomas are rare, clinically-aggressive endothelial tumors with remarkable heterogeneity in terms of anatomical and etiological origins, amongst which UV-radiation and oncogenic viruses have been implicated. Methods: The genomic and transcriptomic landscapes of human angiosarcomas were examined using whole genome sequencing (n = 18) and RNAseq (n = 14). Results were validated in an extended cohort of FFPE tissue (n = 57) on various platforms. Results: We observed recurrent mutations in known angiosarcoma-associated genes including TP53, KDR, POT1 and PTPRB. The median tumor mutation burden (TMB) was 1.95 mutations per megabase and was highest in a subset of head and neck angiosarcomas (HN-AS, n = 6) harboring UV signatures. The remaining cases, including seven HN-AS, contained a significantly lower TMB (5.04 vs 0.91, p= 0.0007). In corroboration, UV exposures were validated by cyclobutane pyrimidine dimer immunohistochemistry in 15 of 35 (42.9%) HN-AS and cutaneous angiosarcomas, but not in visceral or breast angiosarcomas. Gene set enrichment analysis (GSEA) revealed upregulation of “cell cycle” and “inflammation” pathways in angiosarcomas. Notably, drug inhibition of overexpressed kinases including aurora kinase, polo-like kinase and checkpoint kinase-1 potently reduced viability in two angiosarcoma cell lines, achieving IC50s of < 1µM. Metagenomic analysis detected viral reads mapping to the human herpesvirus-7 (HHV-7) genome, which were verified by PCR and immunohistochemistry. Genomic integration of HHV-7 was demonstrated at its flanking DRR telomeric repeat sequence adjoining the subtelomeric region of chromosome 17p. Overall, HHV-7 was detected in 38 of 57 (66.7%) angiosarcomas and inversely correlated with UV exposure ( p= 0.01). GSEA and Nanostring IO360 profiling showed that “inflammation” pathways were enriched in viral-positive angiosarcomas, while “cell cycle” pathways were enriched in viral-negative cases. Compared with HHV-7 negative cases, HHV-7 positive angiosarcomas were associated with high tumor inflammation scores (TIS ≥ median 6.74) (73.3% vs 25.0%, p = 0.02). Conclusions: We identified distinct subtypes of angiosarcoma characterized by HHV7-positive “inflammation” and UV-associated “cell cycle” phenotypes.

11069 Background: Guidelines recommend routine surveillance imaging in patients (pts) following curative resection of STS. However the benefit of such an approach is unclear. We sought to evaluate the utility of a surveillance imaging strategy in pts with localized STS treated with curative intent. Methods: Pts with localized non-indolent STS, seen between 2010 – 2016, who had undergone surgery with R0/R1 surgical margins were included. Epidemiology, treatment and relapse data were collected as was the mode of detection. We defined optimal surveillance as CT/ MRI performed at least 6-mthly following surgery; suboptimal surveillance was defined as CT/ MRI imaging performed less frequently than 6mthly. Results: Of 294 pts included, 31% (n = 92) vs 34% (n = 100) vs 35% (n = 102) had optimal, suboptimal and no routine CT/MRI surveillance imaging respectively. At a median follow-up of 27mths (range 0-79), 36% (n = 105) experienced a relapse; 43% (n = 45) local and 57% (n = 60) had metastatic relapse. More relapses were noted in the optimal surveillance group, 57% (n = 52) vs 28% (n = 28) and 25% (n = 25) in the suboptimal and no surveillance groups respectively (p < 0.001). Within each cohort, relapses detected directly by routine surveillance imaging vs outside of surveillance imaging were as follows: 35% (n = 32) / 22% (n = 20) in the optimal, 17% (n = 17) / 11% (n = 11) in the suboptimal and 0 / 25% (n = 25) in the no surveillance arms respectively. Comparing the 3 strategies, the proportion of pts who then went on to receive curative resection/ metastacectomy was not significantly different, 38% (n = 20), 57% (n = 16) and 32% (n = 8) of relapses, in the optimal vs suboptimal vs no surveillance cohorts respectively (p = 0.1). Notably, routine surveillance imaging directly leading to curative resection occurred only in 15% (n = 14) of pts in the optimal and 9% (n = 9) in the suboptimal surveillance groups. Conclusions: While an intensive routine CT/MRI surveillance imaging strategy detected more recurrences, the impact it has on subsequent resection is less certain. Optimal frequency of surveillance imaging remains unclear.

10051 Background: STS in geriatric pts is not well studied. We evaluated prognostic factors and clinical outcomes in elderly pts with HG STS. Methods: Single centre retrospective study. G-HG STS pts defined as age > 65 yrs seen in our centre from 2002 - 2011 with complete medical records were identified. Charlson age-comorbidity score was assessed for each pt. Results: 116 pts from 4 most common HG STS histo-types representing 69% of pts in the geriatric STS cohort were analysed; leiomyosarcoma (LMS, 14%), non well-differentiated liposarcoma (nWD-LPS, 9%), angiosarcoma (AS, 30%), and undifferentiated pleomorphic sarcoma (UPS, 47%). Median age was 72 yrs, 81% presented with localised disease; of 78% of these localised pts who had curative surgery, 49% received adjuvant therapy, of whom 92% had radiotherapy (RT) only. AS arises more commonly from the head/neck region (p