ESTRO 2021 Abstract Book

S1044

ESTRO 2021

actuarial survival for the whole series was 78% and 85.2%, 87.9%, 44% for low, intermediate and high NAR scores, respectively. In Low-NAR group, 32/36 (88.9%) are still alive, 30/32 (93.8%) of them without disease. 3/36 (8.3%) have died (all due to non-oncological causes) and 1/36 (2.8%) lost follow-up. In Intermediate-NAR group, 62/67 (92.5%) are still alive, 55/62 (88.7%) of them without disease. 4/67 (6%) have died (3/4 (75%) due to non-oncological causes) and 1/67 (1.5%) lost follow-up. In High-NAR group, 17/29 (58.6%) are still alive, 15/17 (88.2%) of them without disease. 12/29 (41.4%) have died, 9/12 (75%) due to oncological disease. Toxicity related to radiotherapy treatment using the aCD (Table 2) was excellent (aCD 1) in 54/132 (40.9%), good (aCD 2) in 74/132 (56.1%), and in 4 patients (3%) who required admission due to rectal bleeding, abdominal sepsis in relation to necrotic tumour and enterocolitis (aCD 3). Surgical tolerance was excellent (CD 1) in 98/132 (74.2%), good (CD 2) in 13/132 (9.8%), 18/132 (13.6%) develop major toxicity (CD 3), 2/132 (1.5%) had severe toxicity (CD 4) and only 1/132 (0.8%) patient development lethal toxicity (CD 5).

Table 1. NAR score related to TRG

Table 2. Surgical CD related to aCD

Conclusion Both NAR and CD scores may be useful in patients with LARC who are undergoing NAT. aCD radiotherapy score may be useful to evaluate acute toxicity during radiotherapy having a common language with surgical toxicity.

PO-1266 Induction chemotherapy in bulky HPV-negative anal canal cancer F. De Felice 1 , A. Fallarino 1 , F. Iafrate 2 , V. Maiuri 1 , G. Galloni 1 , G. Turriziani Colonna 1 , R. De Pietro 1 , G. Chiarello 1 , C. Marchetti 3 , N. Bulzonetti 1 , D. Musio 1 , V. Tombolini 1 1 Sapienza University of Rome, Radiotherapy, Rome, Italy; 2 Sapienza University of Rome, Radiological, Oncological and Pathological Sciences, Rome, Italy; 3 Fondazione Policlinico Universitario A. Gemelli IRCCS , Woman, Child and Public Health, Rome, Italy Purpose or Objective Advanced tumor stage and human papillomavirus (HPV) negativity correlated with worse survival rates in anal canal carcinoma. To prospectively assess feasibility and clinical outcomes of patients with bulky HPV-negative anal canal carcinoma treated by induction chemotherapy and standard chemoradiotherapy. Materials and Methods Patients were enrolled according to the following criteria: i) squamous cell carcinoma, ii) HPV-negative lesion, iii) tumor stage T4 and/or tumor size ≥ 6 cm, iv) with or without node(s) involvement, v) without metastasis, vi) age ≤ 70 years, vii) performance status < 2. Treatment protocol consisted of induction chemotherapy with