ESTRO 2020 Abstract book

S319 ESTRO 2020

This study investigated how to decrease the acute hematologic toxicity (HT) profile in anal cancer patients treated with chemoradiation (CRT), employing a tailored Volumetric Modulated Arc Therapy approach in order to spare hematopoietic bone marrow (BM) identified with (18F)-FDG positron emission tomography (18FDG-PET) Material and Methods A one-armed two-stage Simon’s design was selected to test the hypothesis that BM sparing approach would improve by 20% the rate of G0–G1 (vs G2-G3) HT from 27% of RTOG 0529 historical data to 47% (α=0.05 and the β=0.20). At the first stage, among 21 enrolled patients, at least 9 should have been scored as G0– G1 acute toxicity to further proceed with the trial. At the second stage, another 18 patients will be accrued for an overall sample size of 39 patients. The study was conducted in patients eligible for concurrent CRT following Nigro protocol, dose and constraints of RTOG 0529 trial. We employed 18FDG-PET to identify active BM within pelvic structures (active PBM) detached in 3 subsites: active iliac bone marrow (IBM), active lumbosacral bone marrow (LSBM), active lower pelvis bone marrow (LPBM). Active BM was defined according to the segmentation identifying regions within the pelvis with higher SUV than the mean SUV for that bony region, for each patient. Dose constraints were: V10< 90% and V20<75% for active PBM, V40< 41% and mean dose <32 Gy for active LSBM. Acute HT events and non-hematologic toxicity were recorded. Results From December 2017 to October 2019, 27 patients met the eligibility criteria and were enrolled onto the protocol. In March 2019 we complete the first stage of the trial and we reached the target required by the design of the study and we continued the enrolment. Patients characteristics are shown in the table 1. Ten patients (37%) had stage II disease and 16 (59%) stage III. Five patients experienced grade 3–4 HT,19% versus 58% of historical results; 14 (59%) patients had ≥G2 HT and 13 (48%) patients ≤G1 HT. None of the patients showed grade 3-4 thrombocytopenia. Figure 1 shows trends of hematologic parameters over the 8 weeks from the start of CRT. A total of 66% of patients had G0-G1 gastroenteric toxicity and 78% had urogenital toxicity

Conclusion PET-guided BM sparing IMRT was able to reduce acute HT in anal cancer patients treated with CRT. These results prompted us to conclude the second part of this prospective phase II trial. PD-0537 Factors Affecting Overall Survival in Non- Metastatic Rectal Cancer: An NCDB analysis P. Shaikh 1 , B. Altoos 2 , P. Renz 3 , M. Wu 4 , G. Jacobson 3 , S. Lu 5 1 West Virginia University, Radiation Oncology, Kentwood, USA ; 2 Loyola University, Radiation Oncology, Chicago, USA ; 3 West Virginia University, Radiation Oncology, Morgantown, USA ; 4 Loyola University, Research Methodology, Chicago, USA ; 5 State University of New York at Binghamton, Department of Industrial and Systems Engineering, Binghamton, USA Purpose or Objective To explore the factors that affect OS in patients with non- metastatic rectal cancer using the National Cancer Database (NCDB). Material and Methods The NCDB rectal cancer database was queried for patients with Stage I-III (per AJCC 7 th edition) adenocarcinoma or squamous cell carcinoma treated with radiotherapy and surgery with or without chemotherapy. Patients with missing demographic or tumor data were excluded. The following factors where analyzed to assess their significance in regards to overall survival (OS): facility type (community, comprehensive, academic, integrated cancer center), sex, age (≤50, 51-60, 61-70, >70), Hispanic vs non- Hispanic, insurance status (none, private, medicaid, medicare, other government insurance), median income quartiles (<$38000, $38000-47999, $48000-62999, ≥$63000), Charlson/Deyo score (CDCC, 0-3), grade (1-3), TNM stage, tumor size, number of regional nodes positive, lymphovascular invasion status (LVSI), days from diagnosis to definitive surgery, elapsed days between start and end of radiation, chemotherapy (none, single-agent, multiple- agent, unknown), number of regional node examined, total radiation dose (44-45, 45-50, 50.4-54, >54 Gy). Cox regression model was used for multivariate analysis, and p-values and/or hazard ratio (HR) with 95% confidence interval is presented. Results 14,367 patients in the NCDB database diagnosed between 2010-2015 met the inclusion criteria. Compared to community cancer centers, patients treated at academic cancer centers had a significantly better OS (HR=0.69[0.59-0.81]). Other factors associated with better OS were median income in the top two quartiles (HR=0.84[0.73-0.96] for quartile 3 & HR=0.83[0.72-0.95] for quartile 4), female gender (HR=0.78[0.71-0.86]), combination chemotherapy compared to no chemotherapy