Trastuzumab deruxtecan (T-DXd) has demonstrated efficacy in patients with brain metastasis (BM), a group historically with poor outcomes. The prevalence of BMs in patients commencing T-DXd is currently unknown. No direct comparisons have been made of the activity of T-DXd in patients with active BM versus those with extracranial progression alone. This real-world study explored the prevalence of BMs in patients commencing T-DXd, the efficacy of T-DXd in active BM versus extracranial progression alone and the safety of T-DXd. Patients with human epidermal growth factor receptor 2-positive advanced breast cancer treated with T-DXd between June 2021 and February 2023 at our specialist cancer hospital were identified and notes reviewed. Clinicopathological information, prior treatment, the presence or absence of central nervous system (CNS) disease, outcomes and treatment-emergent adverse events (TEAEs) were recorded. Twenty-nine female patients, with a median age of 52 years (interquartile range 44-62 years), were identified; the prevalence of BM was 41%. Median number of lines of prior therapy was 2 (range 2-6). At a median follow-up of 13.8 months, median progression-free survival (PFS) for the overall population was 13.9 months [95% confidence interval (CI) 12.4 months-not estimable (NE)], 16.1 months (95% CI 15.1 months-NE) for active BMs and 12.4 months (95% CI 8.3 months-NE) for progressive extracranial disease alone. The 12-month overall survival (OS) rate was 74% (95% CI 59% to 95%) in the overall population, and 83% (95% CI 58% to 100%) and 66% (95% CI 45% to 96%) for active BMs and extracranial disease only, respectively. Most common TEAEs were fatigue, alopecia, and constipation. In nine patients (31%, including two deaths), pneumonitis occurred. In this real-world population, we demonstrate T-DXd to be effective in patients with active BMs and those with progressive extracranial disease alone. PFS and OS were numerically longer in those with active BMs. These data demonstrate that patients with active BM treated with T-DXd have at least comparable outcomes to those with extracranial disease alone. The high rate of pneumonitis warrants further consideration.

Background. Randomized studies of neoadjuvant (NA) trastuzumab and pertuzumab combined with chemotherapy for HER2-positive breast cancers (BC) have reported pathological complete response (pCR) rates of 39 to 61. This study aimed to determine the real-world efficacy and toxicity of NA trastuzumab and pertuzumab combined with chemotherapy in a UK tertiary referral cancer centre. Methods. HER2-positive early BC patients given neoadjuvant chemotherapy with trastuzumab and pertuzumab between October 2016 and February 2018 at our tertiary referral cancer centre were identified via pharmacy records. Clinico-pathological information, treatment regimens, treatment-emergent toxicities, operative details, and pathological responses and outcomes were recorded. Results. 78 female patients were identified; 2 had bilateral diseases and 48 of 78 (62) were node positive at presentation. 55 of 80 (71) tumours were ER-positive. PCR occurred in 37 of 78 (46.3; 95 CI: 35.357.2) patients. 14 of 23 (60.8) patients with ER-negative tumours achieved pCR; 23 of 55 (41.8) were ER-positive and 6 of 19 (31.6) were ER-positive and PgR-positive. No cardiac toxicity was documented. Diarrhoea occurred in 53 of 72 (74) patients. Grade 34 toxicity occurred in 2 patients. These were diarrhoea, fatigue, and infection. The Median follow up period was 45.2 months (95 CI 43.846.3) with 71 of 78 (91.0) remaining disease-free and 72 of 78 (92.3) alive. Estimated OS at 2 years 86 (95 CI: 7599). Conclusion. This data confirms the efficacy of neoadjuvant chemotherapy combined with dual HER2 directed therapy. While no cardiac toxicity was observed, diarrhoea occurred frequently. The low pCR rate observed in ER and PgR-positive BCs warrants further investigation and consideration of strategies to increase the pCR rate.

5501 Background: The Dual specificity phosphatases (DUSPs) are a subclass of the protein tyrosine phosphatase (PTP) gene family which appears to be selective for dephosphorylating the critical phosphothreonine and phosphotyrosine residues within the mitogen-activated protein kinases (MAPKs) leading to inactivation. MAPK activation is a downstream target of several oncogenes and may give rise to oncogenic transformation, and hence DUSPs are potential tumor suppressor genes. The aim of this study was to investigate if DUSPs are subject to methylation-dependent silencing in epithelial ovarian cancer. Methods: In this study, promoter methylation and gene expression of the DUSPs genes (DUSP1, DUSP2, DUSP3, DUSP4, DUSP5, DUSP6, DUSP7, DUSP8 and DUSP10) were investigated in 9 ovarian cancer cell lines and in 74 primary epithelial ovarian tumors (Stage III/IV), using methylation specific PCR (MSP) and Reverse- transcription PCR (RT-PCR). The 74 clinical samples were retrospectively retrieved from a large Phase III RCT (the EORTC 55931/NCIC OV10) with clinical follow-up in excess of 6.5 years. Results: Ovarian Cancer Cell lines: Aberrant CpG methylation detected in DUSP1, DUSP2, DUSP4, DUSP6, DUSP7 and DUSP8. DUSP7 promoter methylation was associated with downregulation of mRNA expression. Primary Ovarian Tumors: Methylation of DUSP1, DUSP2, DUSP7 and DUSP8 was observed in 15–38% of the primary tumors. DUSP7 methylation is a predictor of adverse PFS in both univariate (median PFS 10.6 m versus 13.3m, p=0.002) and multivariate (Cox Regression HR 2.76, p<0.001) analyses, and is associated with a trend for poorer OS (22.1 m versus 29.3 m, p=0.07). In contrast, DUSP8 methylation is an independent predictor of favorable PFS (median 23.7m versus 11.5m; Cox Regression HR 0.30, p=0.006) and OS (HR 0.31, p=0.013). 5-year OS for DUSP8 methylated patients was 58.3% compared with 16.1% for DUSP8 unmethylated (HR 0.277, p=0.005). Conclusion: This is the first report of DUSP methylation in epithelial ovarian cancer. The study suggests that methylation-dependent transcriptional silencing of DUSP7 in advanced epithelial ovarian cancer may represent an independent predictor of adverse PFS. DUSP8 methylation, on the other hand, is a favorable clinical outcome marker. No significant financial relationships to disclose.

External Beam Radiotherapy (EBRT) followed by Contact X-ray Brachytherapy (CXB) and vice versa are viable alternatives to surgery for selected rectal cancer patients who have small tumours (≤3 cm). However, the optimal sequence of treatment needs to be established. We compared two approaches using Propensity Score (PS) matching and inverse probability treatment weighting (IPTW) analyses to investigate whether the sequence of treatment affected patient outcomes. This retrospective analysis (2008-2019) included patients with rectal adenocarcinoma (cT1-3,N0-1,M0, grade 1-2, size ≤ 3 cm) who received both EBRT and CXB, irrespective of treatment sequence. PS matching and IPTW were conducted to balance covariate standardised mean differences between groups. Oncological outcomes and rate of post-treatment rectal bleeding were assessed. Following PS matching and IPTW analyses from 251 eligible patients; 103 starting with EBRT (median follow-up: 37 [IQR:18-56] months) and 148 with CXB (median follow-up: 32 [IQR:16-54] months, a significant improvement in 3-year overall survival (77% vs 85%, p = 0.02, [HR:0.58 (95% CI:0.37-0.91)]) and a higher risk of post-treatment rectal bleeding (grade 1 (26%) and grade 2 (6%)) were found in patients who started with CXB (p = 0.08). No significant differences were observed in local regrowth (18% vs 12%, p = 0.47), distant relapse (10% vs 6%, p = 0.53), 3-year organ preservation rates (70% vs 75%, p = 0.20, [HR:0.66 (95% CI: 0.35-1.26)]), or disease-free survival (78% vs 82%, p = 0.17, [HR: 0.47 (95% CI: 0.16-1.38)]) CONCLUSION: In patients with rectal cancer (≤3 cm), commencing with CXB rather than EBRT, was associated with improved overall survival, but had a higher risk of G1/2 rectal bleeding. No statistically significant differences were observed in other oncological outcomes.

Contrary to Pemetrexed-containing chemo-immunotherapy studies, Atezolizumab, Bevacizumab, Carboplatin, and Paclitaxel (ABCP) treatment has consistently shown clinical benefit in prospective studies in patients with lung cancer and actionable mutations, where intracranial metastases are common. Here, we aimed to describe the real-life population of patients fit to receive ABCP after targeted therapy and quantify its clinical effect in patients with brain metastases. Patients treated in Cheshire and Merseyside between 2019 and 2022 were identified. Data were collected retrospectively. A total of 34 patients with actionable EGFR or ALK alterations had treatment with a median age of 59 years (range 32–77). The disease control rate was 100% in patients with PDL1 ≥ 1% (n = 10). In total, 19 patients (56%) had brain metastases before starting ABCP, 17 (50%) had untreated CNS disease, and 4 (22%) had PDL1 ≥ 1%. The median time to symptom improvement was 12.5 days (range 4–21 days), with 74% intracranial disease control rates and 89.5% synchronous intracranial (IC) and extracranial (EC) responses. IC median Progression Free Survival (mPFS) was 6.48 months, EC mPFS was 10.75 months, and median Overall Survival 11.47 months. ABCP in real-life patients with brain metastases (treated or untreated) was feasible and showed similar efficacy to that described in patients without actionable mutations treated with upfront chemo-immunotherapy.

Radical surgery is the standard of care for early rectal cancer. However, alternative organ-preserving approaches are attractive, especially in frail or elderly patients as these avoid surgical complications. We have assessed the efficacy of sole Contact X-ray Brachytherapy (CXB) treatment in stage-1 rectal cancer patients who were unsuitable for or declined surgery. This retrospective multi-centre study (2009–2021) evaluated 76 patients with T1/2-N0-M0 rectal adenocarcinomas who were treated with CXB alone. Outcomes were assessed for the entire cohort and sub-groups based on the T-stage and the criteria for receiving CXB alone; Group A: patients who were fit enough for surgery but declined, Group B: patients who were high-risk for surgery and Group C: patients who had received prior pelvic radiation for a different cancer. With a median follow-up of 26(IQR:12–49) months, initial clinical Complete Response (cCR) was 82(70–93)% with rates of local regrowth 18(8–29)%, 3-year actuarial local control (LC) 84(75–95)%, distant relapse 3 %, and no nodal relapse. 5-year disease-free survival (DFS) and overall survival (OS) were 66(48–78)% and 58(44–75)%. Lower OS was observed in Groups B [HR:2.54(95 %CI:1.17, 5.59), p = 0.02] and C [HR:2.75(95 %CI:1.15, 6.58), p = 0.03]. Previous pelvic radiation predicted lower cCR and OS. The main toxicity was G1-2 rectal bleeding (26 %) and symptoms of impaired anal sphincter function were not reported in any patients. CXB treatment alone achieved a high cCR rate with satisfactory LC and DFS. Inferior oncological outcomes were observed in patients who had received prior pelvic radiotherapy. CXB alone, with its favourable toxicity profile and avoidance of general anaesthesia and surgery risks, therefore, can be considered for patients who are unsuitable for or refuse surgery.