ESTRO 2023 - Abstract Book

S1139

Digital Posters

ESTRO 2023

Results The median follow up time was 11 months. Due to the covid pandemic 4 patients expired and 9 patients defaulted treatment due to lockdown and were not included in the study. During treatment 12 patients developed hemoglobin grade I toxicity in arm I and 5 patient developed grade I toxicity in arm II, 9 patients developed grade II neutropenia in arm I and 3 patients developed grade I neutropenia in arm II & was highly significant (p<0.05). The BM-V10 V20 & V30 of lumbosacral spine (LSS) were less in the VMAT arm (99.69%, 79.74%, 42.97%) when compared to the conventional arm (100%, 95.46%, 85.04% ) and was highly significant (p<0.05). Similar values were seen in the ilium and lower pelvis subsites. Dosimetric parameters involving the LSS and lower pelvis had stronger associations with HT than did those involving the ilium in the VMAT arm. The mean doses received by the rectum and bladder were 52.26Gy and 51.64Gy in conventional arm & 34.42Gy & 40.39Gy in the VMAT arm & the p values were 0.0031 & 0.0038 (highly significant). On long term follow up 9 patients developed radiation proctitis in the conventional arm vs 2 in the VMAT arm. One patient developed local recurrence in the conventional arm. Conclusion Results of this study show that VMAT is safe and effective with a low incidence of acute hematological toxicity. Doses received by the bone marrow especially the LSS & the lower pelvis were higher when compared to other sites. Therefore, there is a need to contour bone marrow as a departmental protocol in gynaecological malignancies. 1 Mount Vernon Cancer Centre, Clinical Oncology, Northwood, United Kingdom; 2 University of Manchester, Division of Cancer Sciences, Manchester, United Kingdom Purpose or Objective Concurrent chemoradiotherapy (CRT) with weekly cisplatin followed by image-guided brachytherapy is the standard of care for locally advanced cervical cancer (LACC). Haematological toxicity (HT) is a significant side effect, leading to interruptions in treatment, dose reductions or chemotherapy omission. Half of active bone marrow lies within the lumbar sacral spine (LS), pelvic bones (PB) and proximal femurs – much of which is inevitably irradiated during treatment. This study aims to investigate the relationship between dosimetry of different irradiated bone regions and HT experienced by patients undergoing radical chemoradiotherapy for LACC. Materials and Methods A retrospective review of patients with LACC who received radical CRT with or without simultaneous integrated boost (SIB at 60Gy) to positive lymph nodes and high-dose rate brachytherapy was conducted. Full blood counts at end of CRT were reviewed to collate haemoglobin (Hb), white cell count (WCC), neutrophil count (NC), lymphocyte count (LC) and platelet count (PC). HT was graded as per CTCAE version 5.0 criteria. Dosimetric data as shown in table 1 for LS (Lumbar spine up to 2cm above PTV in addition to sacrum), PB (Pelvic bones excluding LS and femoral heads) and total bone marrow (TBM – a combination of LS and PB) was recorded. Clinical demographic and dosimetric data were analysed for correlation with risk of HT using univariate and multiple logistic regression models. PO-1410 Dosimetry predictors for haematological toxicity in chemoradiotherapy for cervical cancer M. Abdul-Latif 1 , J. Perera 1 , H. Tharmalingam 1 , Y. Tsang 1 , P. Hoskin 2,1