ESTRO 37 Abstract book

S789

ESTRO 37

Radiation Oncology, Amsterdam, The Netherlands 2 Netherlands Cancer Institute- Antoni van Leeuwenhoek, Surgical Oncology, Amsterdam, The Netherlands 3 Netherlands Cancer Institute- Antoni van Leeuwenhoek, Gastrointestinal Oncology, Amsterdam, The Netherlands 4 Netherlands Cancer Institute- Antoni van Leeuwenhoek, Pathology, Amsterdam, The Netherlands Purpose or Objective Neoadjuvant chemoradiotherapy (nCRT) and surgery form the base of a potentially curative treatment of resectable oesophageal cancer. For a majority of patients this intensive treatment provides long term survival. In contrast, about 20% dies within one year after treatment, mostly from distant metastases. Tumour markers, such as CEA and CA19-9, play no role in the current management of oesophageal cancer, whereas for other gastrointestinal tumours such as colon cancer (CEA) or pancreatic cancer (CA19-9) tumour markers are used as prognostic markers and during follow-up. In this study, the prognostic impact of elevated baseline CEA and CA19-9 levels were analysed in relation to overall survival (OS), disease recurrence and early treatment failure (ETF). Material and Methods Oesophageal adenocarcinoma patients who were planned for treatment with nCRT and surgery in the Netherlands Cancer Institute between 1998-2014 were included if both CEA and CA19-9 levels were measured before the start of treatment. Clinical data, treatment specifics and follow up data were retrieved retrospectively. NCRT consisted of radiotherapy (41,4-50Gy in 23-25 fractions) in combination with concurrent carboplatin/paclitaxel or 5-fluorouracil/cisplatin and was followed by an oesophagectomy after 6-8 weeks. Endpoints of interest were OS, time to disease recurrence and ETF, which were calculated from the start of nCRT until the date an event occurred and computed with Cox models. ETF was defined as recurrence or death within one year after surgery, thus 15 months after start of nCRT. Patients with normal baseline CEA (<6µg/l) and CA19-9 (<37kU/l) were compared to those with elevated tumour markers. Results In total, 102 patients with a median follow-up of 5.7 years formed the study cohort. Median OS was different (p<0.001) between patients with normal CEA and CA19-9 levels (n=59; 51 months, 95%CI: 29-73), patients with elevated CEA (n=13; 43 months, 95%CI: 9-78) or CA19-9 (n=19; 24 months, 95% CI: 12-35) levels and patients with elevation of both CEA and CA 19-9 (n=11; 11 months, 95%CI: 7-14). In multivariable analysis, correcting for statistically significant factors for OS in univariable analysis (i.e., comorbidity score, clinical T and N stage, BMI and completing treatment as planned), elevated CEA and CA19-9 levels remained associated with shorter OS (both markers versus no markers elevated, HR: 2.864; 95%CI 1.328 – 6.180, p=0.007). Time to recurrence was 34 months when no markers were elevated, and 7 months when both were elevated (p=0.003). Elevation of CEA and CA19-9 at diagnosis was associated with early treatment failure (OR: 10.444; 95%CI 2.400–45.450, p=0.002). Conclusion Elevated levels of CEA and CA19-9 prior to nCRT for oesophageal adenocarcinoma were associated with early treatment failure and decreased overall survival. When both markers are elevated at baseline, the benefits of surgery might not outweigh the down-sides.

Fig. 1 Overall survival of patients with oesophageal adenocarcinoma (n=102).

EP-1451 Stereotactic body radiation therapy (SBRT) in pancreatic cancer (PCA): a single centre experience N. Simoni 1 , R. Micera 1 , A. Muraglia 1 , M. De Liguoro 1 , L. Cernusco 1 , S. Guariglia 2 , E. Zivelonghi 2 , C. Cavedon 2 , R. Mazzarotto 1 1 Azienda Ospedaliera Universitaria Integrata Verona, Radiation Oncology, Verona, Italy 2 Azienda Ospedaliera Universitaria Integrata Verona, Medical Physics Unit, Verona, Italy Purpose or Objective SBRT is an emerging treatment option for borderline resectable (BRPC) and locally advanced (LAPC) PCA, that allows to deliver high radiation doses within a few fractions to the tumor, sparing the surrounding critical organs at risk (OARs). The aim of this study was to evaluate the effectiveness, in terms of local control rate (LCR), overall survival (OS) and progression-free survival (PFS), as well as SBRT toxicity in PCA patients (pts). Material and Methods We retrospectively reviewed 20 pts with PCA (10 BRPC, 10 LAPC) treated from October 2016 to July 2017 at our Institution. All pts received induction chemotherapy prior to SBRT (10 Folfirinox, 10 Gemcitabine-Paclitaxel). For each patient a custom made abdominal compressor was used to reduce breathing induced tumor motion. Contouring of the gross tumor volume (GTV) was performed by a 4 phase contrast-enhanced simulation computer tomography (CT). The Internal Target Volume (ITV) was defined as the envelope of the GTVs from each CT phase. An ITV-to-PTV (Planning Target Volume) margin of 5 mm was applied. For the OARs (duodenum, stomach, bowel) we used a 3 mm expansion planning organ at risk volume (PRV). The SBRT was delivered in 5 consecutive daily fractions, prescribing 30 Gy to the PTV (6 Gy/fraction), while simultaneously delivering 50 Gy (10 Gy/fraction) inside the ITV. We reduced the dose to 25 Gy (5 Gy/fraction) on the overlap area between the PTV and the PRV OARs, to limit the toxicity. Elective nodes were not included in the treatment volume. The SBRT was delivered with Volumetric Modulated Arch Therapy (VMAT) using a Varian DHX LinAc (13 pts) or with TomoTherapy (7 pts). Daily volumetric image-guided RT was performed. Restaging CT were performed at 4 weeks, and subsequently pts were considered for resection.