ESTRO 2022 - Abstract Book

S227

Abstract book

ESTRO 2022

14 Radiotherapy and medical oncology center, Radiotherapy, Béziers, France; 15 Institut Curie, Medical Oncology, Paris, France; 16 EPICAD INSERM LNC-UMR 1231, University of Burgundy, gastro-enterology, Dijon, France; 17 St Louis Hospital, APHP, Radiotherapy, Paris, France Purpose or Objective Evaluation of clinical practice, treatment and outcome after treatment of squamous cell carcinoma of the anus (SCCA) in the French national cohort ANABASE. Materials and Methods This prospective national multicentric observational cohort included all patients (pts) treated for SCCA in 60 French centers from January 2015 to April 2020. Pts were treated according to French guidelines and local expertise of each center. Pts and tumor characteristics, treatments (chemotherapy (CT), radiotherapy (RT), and surgery) and outcomes were analyzed as well as colostomy-free, disease-free and overall survivals at 3 years. Univariate and multivariate analyses were performed by logistic regression in order to determine factors associated with survival. Results Among 1097 pts treated for a non-metastatic SCCA, 1015 pts with complete data were analyzed . Pts characteristics were as follow: median age: 65 years (range 32-94); gender: 248 males (24.4%) and 767 females (75.7%); HIV serology: positive 86 pts (17.6%), negative 402 (82.4%), among 488 pts with known status. Tumors were classified as locally limited (T0-1-2, N0, M0) for 440 pts (43.3%) and locally advanced (T3-4 or N+, M0) for 575 pts (56.7%). Regarding RT treatment, IMRT was used for 80.2% versus 3D for 19.8% of pts. Median total dose was 60 Gy (range 18-79), 150 pts had a brachytherapy boost. An interruption of treatment was made for 327 pts (32.2%), with a median duration of 14 days, because of toxicity in 47.4% of cases but mostly as planned gap in 52.6 % of cases. A concomitant CT was administered for 803 pts, including mitomycin- based CT for 86.2%, cisplatin-based CT for 3.6% and 5FU alone for 4.4%. An induction CT before RCT was administered for 70 pts (6.9%). Median follow-up was 35.5 months [IC 95%: 34.4;36.0]. Overall survival, disease-free and colostomy-free survival at 3 years were 91.7% [95%CI: 88.0-94.2], 84.3% [95%CI: 80.1; 87.8] and 85.8% [95%CI: 81.6; 89.1] respectively for pts with locally limited tumors (T0-1-2, N0, M0) compared to 78.2% [95%CI: 73.6-82.1], 64.4 % [IC95% : 59.7; 68.7] and 67.3 % [IC95% : 62.5; 71.6] respectively for pts with locally advanced (T3-4 or N+, M0). Patient gender (male), OMS condition, HIV positive status and locally advanced tumors were significantly associated with poor DFS and CFS in multivariate analysis. Only male gender, HIV positive status and OMS condition were associated with OS. A specific complementary analysis was done for HIV patients. A recurrence occurred in 202 patients: local or nodal in the pelvis for 115 pts (56.9%), metastatic for 72 pts (35.6%) or both for 12 pts (5.9%). Salvage surgery (abdomino-perineal resection) was done for 90 pts. Conclusion Final results of the ANABASE cohort showed a good accordance with actual guidelines for anal cancer treatment with the use of IMRT treatments and mitomycin-based chemotherapy for more than 80% of pts. An improvement in the management of SCCA is mandatory for HIV-positive pts and pts presenting with locally advanced tumors. 1 Aarhus University Hospital , Department of Experimental Clinical Oncology, Aarhus, Denmark; 2 Aarhus University Hospital, Department of Experimental Clinical Oncology, Aarhus, Denmark; 3 Aarhus University Hospital, Department of Pathology, Aarhus, Denmark Purpose or Objective Purpose: Tumor hypoxia is related to reduced radiosensitivity in squamous cell carcinomas (SCC). A 15- gene hypoxia classifier has shown prognostic value in SCC of the uterine cervix and predictive value for hypoxia modifying treatment in head and neck SCC (HNSCC). The aim of this study was to investigate the prognostic value of the 15-gene hypoxia classifier on loco-regional tumor control in SCC of the anus (SCCA). Materials and Methods Material: Diagnostic biopsies were collected from 2016-2019 from 79 newly diagnosed SCCA patients. All biopsies were formalin fixed and paraffin embedded with histologically verified, invasive SCC. Each tumors expression of the 15 hypoxia genes was scored using the method defined by DAHANCA (Toustrup K, Acta Oncol. 2016). A 70% cut-off was used for p16 overexpression. Patients were treated with high dose chemo-radiotherapy (CRT) with 60 – 64 Gy to tumor and pathological nodes and 49.5 – 51.2 Gy to CTV, delivered in 30-32 fractions with concomitant cisplatin-based chemotherapy, according to national Danish guidelines. Persistent disease was defined as pathological verified SCC < 6 months after CRT, and loco- regional failure was pelvic failure or inguinal node failure > 6 months after CRT. Fisher’s Exact test, Cox regression and competing risk analysis were used. Results Results: Classification of the 15 genes was conclusive in all biopsies with 53 (67%) “less” hypoxic tumors and 26 (33%) “more” hypoxic tumors. Comparison of the mean expression levels for the 15 genes showed similar expression levels for the SCCA samples as for HNSCC and SCC of the uterine cervix (figure 1) and was unrelated to p16 status. Tumor stages were 22% T1, 58% T2, 8% T3 and 10% T4, respectively. Node involvement was found in 23%, and p16 overexpression was detected in 82% of the tumors. Patient and tumor characteristics were equally distributed between the “less” – and “more” hypoxic groups. After a median follow-up time of 42 months (range 9 – 66), eight patients (10%) had loco-regional treatment failure, including five patients with persistent disease. Four of five persistent patients had a “more” hypoxic tumor, resulting in a significantly increased risk of persistent disease for “more” hypoxic tumors compared to “less” hypoxic tumors, p = OC-0271 Hypoxia in anal cancer – a hypothesis generating study using a 15-gene hypoxia classifier A.C. Lefèvre 1 , J. Alsner 2 , B.S. Sørensen 2 , T. Tramm 3 , K. Toustrup 2 , J. Overgaard 2 , K.G. Spindler 2