ESTRO 36 Abstract Book

S172 ESTRO 36 _______________________________________________________________________________________________

Purpose or Objective As result of the aging population, increasing life expectancy and increasing rectal cancer incidence, more elderly patients will undergo treatment for rectal cancer. Neoadjuvant (chemo)radiotherapy and surgery are associated with considerable morbidity and mortality. In this study we compared treatment course, postoperative complications and quality of life (QoL) in older versus younger rectal cancer patients. Material and Methods All patients within the Dutch prospective colorectal cancer cohort with primary rectal cancer referred for Radiotherapy at the UMC Utrecht between February 2013 and January 2016 were selected. QoL was assessed with the EORTC-C30 questionnaire before start of neoadjuvant treatment and at 3, 6 and 12 months afterwards. Patients were divided into elderly (≥70 years) and non-elderly (<70 years). Differences in QoL were analyzed with generalized estimation equations, adjusted for baseline score, and stratified according to presence of postoperative complications. Results A total of 115 elderly (33.3%) and 230 non-elde rly (66.6%) patients were included. Compared to non-eld erly, elderly patients were less often male (62.6% vs. 75.2%), had more often previous abdominal surgery (40.9% vs. 30.0%) and presence of comorbidities (80.0% vs. 59.1%). Elderly were more likely to undergo short-course radiation with delayed surgery and less likely to undergo chemoradiation (resp. 19.1% and 39.1% vs. 6.1% and 62.6% in non-elderly, p<.001). Surgery was performed equally in both groups (83.5% in elderly vs. 87.8% in non-elderly, p=.318). The reasons for no surgical treatment, included disease progression and poor performance status in elderly, and disease progression or a wait-and-see policy in non- elderly. No differences were observed in postoperative complications between elderly and non-elderly (surgical- and non-surgical complication rate 36,5% vs. 34,7%, p=.780), neither when stratified for type of neoadjuvant therapy or surgical procedure. Trends of functional QoL domains were similar between elderly and non-elderly during the first year after diagnosis with lowest scores at 3 and/or 6 months. In elderly, postoperative complications had a stronger impact on physical- and role functioning (at 6 months resp. MD -19.2 and -18.4, relative to non-elderly with postoperative complications) (Figure 1). In a sensitivity analysis, comparing patients >80 years with younger patients, comparable results were observed.

PV-0328 Factors associated with complete response after brachytherapy for rectal cancer; the HERBERT study. E.C. Rijkmans 1 , R.A. Nout 1 , E.M. Kerkhof 1 , A. Cats 2 , B. Van Triest 3 , A. Inderson 4 , R.P.J. Van den Ende 1 , M.S. Laman 1 , M. Ketelaars 1 , C.A.M. Marijnen 1 1 Leiden University Medical Center LUMC, Department of Radiotherapy, Leiden, The Netherlands 2 The Netherlands Cancer Institute, Department of Gastroenterology and Hepatology, Amsterdam, The Netherlands 3 The Netherlands Cancer Institute, Department of Radiotherapy, Amsterdam, The Netherlands 4 Leiden University Medical Center LUMC, Department of Gastroenterology and Hepatology, Leiden, The Netherlands Purpose or Objective The HERBERT study was performed to examine the feasibility of a high hose rate endorectal brachytherapy (HDREBT) boost after external beam radiotherapy (EBRT) in elderly patients with rectal cancer who were unfit for surgery. The primary results and long term clinical outcomes have been presented at ESTRO 2014 and 2016. With rising interest for organ preservation, the role of definitive (chemo)radiotherapy becomes increasingly important. This current analysis evaluates factors that are associated with a complete response to treatment. Material and Methods A dose finding feasibility study was performed from 2007 to 2013 in inoperable rectal cancer patients. Patients received 13x3 Gy EBRT followed by three weekly applications HDREBT of 5 to 8 Gy per fraction. Clinical target volume (CTV) for HDREBT was defined as residual scarring or tumor after EBRT. Clinical tumor response was evaluated based on digital rectal examination and endoscopy (MRI or biopsy was not routinely performed). Complete response was determined after serial assessments. Patient, tumor and treatment characteristics of complete responders (CR) were compared to non-complete responders (nCR) using Chi- square test and the independent samples t-test. Results Of the 38 patients included in the study 33 were evaluable for response evaluation. Seven were treated with 5 Gy per fraction, four with 6 Gy, 12 with 7 Gy and 10 with 8 Gy per fraction. In total 20 patients achieved a complete response. Baseline patient characteristics (age, ASA, WHO and co-morbidity) and tumor-characteristics (T-stage, N- stage, cranio-caudal length of the tumor and distance from anal verge) were not associated with response to treatment. A trend was observed in complete response between dose levels; 2/ 7 treated with 5 Gy per fraction; 1/4 with 6 Gy; 9/12 with 7 Gy and 8/10 with 8 Gy per fraction (p=0.05). The actual planned D98 (dose to 98% of the CTV) was however not significantly different between patient with a complete response and no complete response: 6.25 Gy (range 3.8-8.3 Gy) vs. 5.98 Gy (range 1.2-8.8 Gy) respectively (p=0.63). Endoscopic evaluation of response after EBRT was significantly associated with the overall response rate. Seven patients already had a CR after EBRT, whereas 13/21 patients (62%) with a partial response after EBRT achieved a CR. None of the five patients with stable disease achieved a complete response (p=0.002). Mean residual volume and thickness of residual scarring or tumor after EBRT were significantly lower in complete responders (see Figure). In addition, tumors encompassing less than 1/3 of the circumference were more likely to achieve a complete response than larger tumors (70% vs 17% respectively, p=0.025).

Conclusion Elderly are more often treated by less invasive treatments, which deviates from the standard treatment. Compared with younger patients, elderly have similar postoperative complication rates. Nevertheless, the impact of postoperative complications on physical- and role functioning is stronger in elderly than in younger patients. These results suggest a need to predict the frailest elderly patients who are at risk for postoperative morbidity and hereby an impaired quality of life.