ESTRO 2023 - Abstract Book

S1134

Digital Posters

ESTRO 2023

The new Standard of care in Locally advanced rectal cancer (LARC) included Total neoadjuvant treatment(TNT) intensive neochemotherapy with short course Radiotherapy (scRT) followed by surgery. This new approach achieves the doble (28%) of completed pathological response (pCR) than conventional RTQT schedules. The aim of this study is to analyze if regional-hyperthermia (RHT) can improve pCR and complete resection rates(R0) without increased toxicity related to oncological treatment. Materials and Methods We conducted a feasibility study including patients with LARC treated with TNT, scRT and RHT at HUGCDN in March 2020 February 2022. scRT schedule with a total dose of 25 Gy in 5 consecutive fractions (fx), was delivered by VMAT and IGRT with AL Truebeam VARIAN, combined with FOLFOX4 or CAPEOX chemotherapy (CT) 2-3 weeks later. RHT were administered by Deep Hyperthermia SYSTEM _ ALBA 4D, in session 1 and 5, 40 minutes after RT-fx, reaching tumor temperatures between 39-43ºC for 60minutes. Surgery was performed 4-6 weeks after CT. Analysis of the pCR rate was based on histopathological reports. Acute side effects were documented according to CTCAEv4.0. Results 25 patients were included (5 patients are in course of CT, 1 waiting for surgery), with a mean age 60 (41-80years), Stage II 4% (1/25), Stage III 80% (20/25), and Stage IV 16% (4/25). Most of the patients 76%(19/25) received 2 scheduled RHT sessions, 76%(19/25) had already undergone surgery. The pCR was 32% (6/19) and R0 rates was 79% (15/19). The prevalence of immediately acute toxicity after scRT(<1month) grade 0 56%(14/25), grade1 28%(7/25), grade2 8%(2/25), grade 3 were 8%(2/25) non ≥ 4. Conclusion This initial result shows that the addition of RHT in scRT in TNT schemes in LARC may improve the pCR rates, without increase immediately scRT toxicity. Further studies are needed to confirmed this benefit. 1 Universidad de Valparaiso, Radiation Oncology, Valparaiso, Chile; 2 Hospital Carlos Van Buren, Radiation Oncology, Valparaiso, Chile Purpose or Objective Total neoadjuvant therapy (TNT) is an approach consisting in the delivery of radiotherapy and systemic chemotherapy in their entirety before surgery. It’s one of the current standards for the treatment of locally advanced rectal cancer (LARC). The purpose of this study is to describe the result of TNT at the Carlos Van Buren Hospital (Valparaíso, Chile). Materials and Methods This retrospective cohort includes patients treated with curative intent for LARC between 2017 and 2021. TNT was administered as short course radiotherapy with a prescription of 25 Gy in 5 daily fractions, followed by medical oncologist’s choice of FOLFOX or XELOX, then surgery. Overall survival is measured from start of radiotherapy. As follow-up of previous work (PO-1322 at ESTRO 2022), neoadjuvant rectal (NAR) score, initially proposed by George et al. (2015), was calculated for patients with available clinical and surgical staging and modelled against death events up to 36 months using logistic regression and ROC curve analysis. Statistical analysis was made in Stata v17 (Statacorp, 2022). Results The current cohort includes 107 patients. Initial local staging was reported as cT2 in 6.6% of patients; cT3 in 69.8% and cT4 in 23.6%, with an 84% of nodal involvement (cN1-2). All patients were staged with a CT scan, and 85% had a pelvic MRI. Median duration of radiotherapy was 5 days (IQR 5-7), with a median interval between end of radiotherapy and surgery of 112 days (IQR 94-150). In between, a median of 3 cycles of chemotherapy were administered (IQR 2-3). Surgical staging was retrieved for 81 patients, reporting 24.7% ypT0 patients; 4.9% ypT1; 17.3% ypT2; 43.2% ypT3 and 9.9% ypT4. Nodal staging was ypN0 in 76,5%. Overall, 21% were staged as ypT0N0, also denominated complete pathological response (pCR). Median follow-up was 36.7 months (IQR 21.1-42.5), with a 3-year overall survival of 69.9% (CI 95% 59.3-78.3). Patients with available surgical biopsy had a 3y-OS of 76.9% (CI 95% 64.9-85.3); those achieving a pCR had a 3y-OS of 100%, registering a single event at 40-months. By comparison, patients without a pCR had a 3y-OS of 70.7% (CI 95% 56.4-81) (p-logrank = 0.0405). (Figure 1) Figure 1.- OS for the whole cohort and by pCR PO-1405 Total neoadjuvant therapy for rectal cancer – Experience of the Carlos Van Buren Hospital G. Lazcano Álvarez 1 , I. Perrot Rosenberg 2 , J. Solis Campos 1 , B. Tudela 1 , G. Veillon Contreras 1 , L. Gonzalez Abascal 1