ESTRO 2021 Abstract Book

S1088

ESTRO 2021

fractions and 5 receiving 78Gy in 39 fractions. This group was compared with 25 patients receiving the same dose fractionation schedules immediately prior to the implementation of gel spacer use i.e. without gel spacers in situ. Rectal doses were compared using V60, V40 and D2cc for the 60Gy group, and, V75, V50, D2cc for the 78Gy group. The maximum grade of prospectively collected acute GI toxicity (CTCAE v4.0) was also compared between the two cohorts. Patient records were assessed for procedure-related complications. Results All metrics of rectal dosimetry were significantly lower in the gel spacer cohort for the 60Gy group (see table 1). Only the D2cc was significantly reduced in the 78Gy group, although numbers in this group were very small. The maximal grade of acute GI toxicity was reduced in the spacer group (see figure 1). There were 2 minor procedure-related complications, a vasovagal episode post-placement and a further patient required laxatives for several days post gel placement.

Conclusion The implementation of gel spacer placement prior to prostate radiation resulted in significant reductions in rectal dose metrics for patients treated with moderate hypofractionation. Acute toxicity was lower with spacer use. This limited early experience of gel spacer use is encouraging for the lack of procedure-related complications to date. Longer term follow-up is required to assess late toxicity and patient-reported outcomes. PO-1327 Prostate cancer radiotherapy in a COVID-19 pandemic year: experience of a chilean public hospital H. Letelier 1,2 , C. Herrera Bovet 1 1 Hospital Clinico Regional de Valdivia, Oncology and Radiotherapy, Valdivia, Chile; 2 Universidad Austral de Chile, School of Medicine, Valdivia, Chile Purpose or Objective The Covid-19 pandemic has challenged cancer management around the world. In an attempt to mitigate this, several recommendations have emerged to prioritize the most life-threatening cancers and more efficient fractionation programs have been encouraged. Prostate cancer (PC) is the most prevalent neoplastic disease in Chilean men (28.3%) and one of the main indications of radiotherapy (RT). Despite their good behavior in most cases, deferring treatment of a high volume of patients could represent a risk for an active and long-lived population. Our RT Unit is one of 7 public centres in Chile. We treat around 1300 patients per year from southern regions of the country (approx 2.5 million inhabitants). We established a policy of rapid adaptation of hypofractionation (HF) schemes, in accordance to evidence and experts recommendations. We report and analyze the management of patients with PC in 2020 comparing it with the previous year. Materials and Methods This is a review of all PC patients treated with curative intention RT in our department between 1 January 2019 and 31 December 2020. We analyzed data from the 2019 and 2020 cohorts. Although the COVID-19 "state of emergency" began in March 2020, we decided to include the entire year, because some treatments that started earlier were still