ESTRO 2020 Abstract book

S716 ESTRO 2020

PO-1269 Intensity Modulated Radiotherapy for pelvic tumors in elderly patients with colic diverticulosis F.C. Di Guglielmo 1 , D. Fasciolo 1 , F. Patani 1 , L. Gasparini 1 , A. Allajbej 1 , C. Bonfiglio 1 , C. Rosa 1 , L.A. Ursini 1 , M. Trignani 1 , A. Vinciguerra 1 , L. Caravatta 1 , D. Genovesi 1 1 SS.Annunziata Hospital G.D' Annunzio University, Radiation Oncology, Chieti, Italy Purpose or Objective In the last few decades radiotherapy (RT) resulted as an effective and widely used treatment for the management of pelvic tumors. Currently, over 50% of tumors are diagnosed in patients aged 65 years or over. Most of published studies have demonstrated RT feasibility in curative intent for elderly patients, showing heterogeneous results related to different tumor location, multimorbidities, performance status, social support, and physiological age-related changes. Colic diverticulosis represents a widespread condition, whose prevalence is increasing especially in elderly population. Unfortunately, specific dose-constraints are not currently available for treatment planning of these patients. In this scenario, the aim of this study was to assess the impact of diverticulosis on gastrointestinal toxicity in era of modern radiotherapy in patients older than 65 years. Material and Methods A retrospective analysis was conducted on 32 patients with diagnosis of uncomplicated diverticulosis, which underwent pelvic RT in our Institute between 2015 and 2018. Organs at risk (bowel bag and sigma) were delineated according to RTOG guidelines in the treatment field, at least 1 centimeter above the Planning Treatment Volume (PTV). A review of Scientific Literature was performed on Pubmed with the aim of identifying the available reference constraints for bowel (large and small bowel, sigma and/ or rectum). Results Median age was 70.3 years with a range of 67-86 years. All patients underwent pelvic irradiation for treatment of gynecological, prostatic, anal or rectal cancer (total dose range 4500-7800 cGy). All treatments were delivered by Intensity Modulated Radiation Therapy (IMRT) or Volumetric Modulated Arc Therapy (VMAT). Clinical and treatment features and reported toxicity are summarized in Table 1. Overall, 12 patients (37%) experienced G1 acute intestinal toxicity (diarrhea) and 8 (25%) G2 toxicity (diarrhea, proctitis), according to RTOG scale. None acute toxicity > G2 was recorded. With a median follow-up of 5 months (3-38), none sub-acute or late intestinal toxicity was reported. Dosimetric parameters from the Dose-Volume histogram analysis are detailed in Table 2. The median Bowel bag volume was 2511,5 cc with a median V45 of 57cc; the median Sigma volume resulted of 78,7 cc with a median V50 of 0,22 %.

Conclusion Preliminary results on a small number of patients confirmed that VMAT and IMRT allow to spare the amount of Sigma and Bowel Bag volumes receiving high doses. Elderly patients with diverticulosis experienced a gastrointestinal toxicity comparable to standard population after pelvic irradiation. The analyzed dosimetric parameters resulted to be correlated to a low grade of gastrointestinal toxicity.The study is still ongoing to confirm these results on a larger sample of patients with a longer follow-up, in order to suggest dosimetric parameters useful for clinical practice. PO-1270 Accelerated partial breast irradiation with HDR brachyterapy in elderly breast cancer patients. P. Lelek 1 , S. Kellas-Ślęczka 1 , T. Krzysztofiak 1 , M. Stankiewicz 1 , M. Fijałkowski 1 , P. Wojcieszek 1 1 Maria Skłodowska- Curie Memorial Cancer Center and Institute of Oncology Gliwice, Brachytherapy Department, Katowice, Poland Purpose or Objective To report the long term results of elderly patients ( 75 years of age and older) treated in the II-phase prospective trial on accelerated partial breast irradiation efficacy using interstitial multicatheter high-dose-rate brachytherapy (HDR-BT) after breast-conserving surgery. Material and Methods A total of 425 patients with low-risk invasive and in situ carcinoma after BCS were treated using interstitial multicatheter HDR brachytherapy technique in our department between June 2006 and August 2019. The total dose was 32 Gy in 8 fractions delivered twice-daily with a minimum 6-hour break. There were 32 elderly patients enrolled in this study. The COIN and DHI indexes were calculated. Local recurrence and toxicity were evaluated. Results The median age was 78 years ( range 75-85 years). The median follow-up was 44 months (range 1-120 months). The treatment was well tolerated. There were no complications associated with the procedure, and all of the patients completed the treatment without interruption. The mean volume of the PTV was 61 cc., with the mean value of its coverage with the prescribed dose amounting to 94% The mean conformity index (COIN) was 0,68, and the mean dose homogeneity index (DHI) was 0,64. The mean value of the maximum skin dose was 49% of the prescribed dose. The mean value of the ipsilateral lung dose to 2cc volume was 36,7% of the prescribed dose and to 10 cc volume was 27%. The mean maximum dose for the closest rib was 60 % of the prescribed dose.