Abstract Book

S798

ESTRO 37

EP-1471 induction chemotherapy followed by chemoradiotherapy in locally advanced anal canal carcinoma I. Benevento 1 , M. Venezia 1 , L. Mistrulli 1 , F. De Felice 1 , D. Musio 1 , R. Caiazzo 1 , V. Tombolini 1 1 Policlinico Umberto I "Sapienza" University of Rome, Radiation Oncology, Roma, Italy Purpose or Objective Concomitant chemoradiotherapy (CRT) is the standard for locally advanced anal canal carcinoma (LAACC). Several studies identified clinical features, as large primary tumors and extensive regional nodal involvement, associated with poor prognosis and failure of the standard CRT. The aim of our study is to evaluate the impact of induction chemotherapy (ICT) in LAACC patients with large primary tumors, involvement of perianal skin and adjacent organs and extensive regional nodal disease. Material and Methods Patients with histologically proven squamous carcinoma of the anal canal staged clinically T4N3M0 were eligible. All patients underwent temporary colostomy. ICT consisted of 3 cycles of Cisplatin (CDDP) (75mg/m2 q28) plus 5-FU (750 mg/m2/d as ci). CRT consisted of 2 cycles of Mytomicin C (MMC) and 5-FU. RT was delivered using IMRT at 45 Gy in 25 fractions to pelvic and inguinal nodes; an additional 14 to 23.4 Gy (1.8 Gy/die 5/w) were delivered to primary tumour and involved nodes. After ICT and 3 months after CRT, clinical response was assessed with CT and MRI. Primary endpoints were local control (LC), symptomatic improvement and treatment feasibility. Results Between January 2007 and December 2016, 84 patients with anal canal cancer were treated. Four of them presented with a T4N3M0 clinical stage, a 10 cm median tumor longitudinal extension (range 7-12) and involved perianal skin. All patients were female, median age 62 yrs, with pelvic pain (VAS 5-8) and infected perianal wounds. All patients completed ICT, achieving complete pain resolution. No toxicity was recorded, with the exception of anemia (G1) in 1 patient. Restaging MRI showed partial response (PR) in all patients. CRT was completed without interruptions nor severe toxicities: dysuria, radiodermatitis and diarrhoea G1 were recorded. At the 3 months CRT evaluation, there were 1 complete response and 3 PR. Of those 3 patients, 1 gained CR, 1 showed local disease progression and underwent Miles’ resection and 1 presented lung metastases, at 6 months follow-up. After a median follow-up of 16 months (range 13-46), all patients were alive: 2 had LC and 2 had LC with distant metastases. Conclusion The patients enrolled in this study had a local disease so advanced that even a Miles’ resection cannot be performed. As a palliative strategy for patients with LAACC is currently missing, we candidated our patients to the previously described ICT. The RTOG 9811 trial failed to improve disease free survival with 5-FU/CDDP ICT followed by 5-FU/CDDP/RT compared to the standard treatment. However, in this trial most patients had clinical T2 or T3 disease and only a few had tumors greater than 5 cm and/or positive nodes. Also notable, the experimental arm did not contain MMC. Although in a selected group of patients, the ICT in our study achieved a stable LC, rapid symptoms improvement and a significative disease volume reduction, that made the RT more feasible, both technically and clinically.

Tbilisi, Georgia 5 Research Institute of Clinical Medicine, Chemotherapy Departmant, Tbilisi, Georgia 6 Research Institute of Clinical Medicine, Chemotherapy Department, Tbilisi, Georgia Purpose or Objective For locally advanced rectal cancer (LARC) preoperative chemoradiotherapy (PCRT) followed by surgery is preferred as the best treatment option. Neoadjuvant chemoradiotherapy with a total dose of 50.4Gy is a standard treatment for patients with cT3-T4 rectal cancer. Radiotherapy (RT) field for LARC is recommended to encompass the primary tumor, entire mesorectum, presacral space, and regional lymph nodes. Simultaneous integrated boost (SIB-VMAT) can increase the fraction dose to the boost volume, keeping the dose to the elective volume at a lower level, and providing clinical and dosimetric advantages. There are several clinical trials of PCRT for LARC using SIB-VMAT, reporting good oncologic outcomes with same toxicities. Based on these clinical data, we commenced SIB-VMAT for PCRT in LARC. Aim of the preoperative concurrent chemotherapy and VMAT-RT intensified with SIB dose escalation was to evaluate resectability and pathological response – early clinical outcome. Material and Methods In Research Institute of Clinical Medicine from February, 2015 87 patients with c T3-T4 rectal cancer were treated preoperatively with IG-VMAT (45Gy in 25 fractions and additional boost 5.4Gy in 3 fractions). From September, 2016 57 patient with c T3-T4 rectal cancer were treated with SIB technique, 46Gy to the elective volume and 57.5Gy as a boost to the rectal tumor in 23 fractions, plus capecitabine 825 mg/m2 twice daily. Pelvic MRI was performed after 6 weeks and surgery was performed 8 weeks after completion of preoperative treatment. Tumor size reduction on MRI after 6 weeks was the primary endpoint. Secondary endpoint was post-operative morphologic evaluation. Acute toxicities were evaluated according to CTC-AE v.3.0 criteria. Results All patients enrolled in both arms underwent radical surgical resection. Tumor response was evaluated according to the RECIST criteria. R0 resection was achieved in all patients. In standard arm cT0N0 was reached in 61 patients (70.1%), primary tumor clinical downstaging was observed in 19 patients (21.8%) and disease stability was achieved in 7 patients (8.1%). Complete pathological response was observed in 44 patients (50.6%)- pT0N0 disease in 33 patients and pTmic in 11 patients. In SIB arm cT0M0 was reached in 51 patients (89.5%), primary tumor clinical downstaging was observed in 5 patients (8.8%) and disease stability was achieved in 1 patient (1.7%). Complete pathological response was observed in 45 patients (78.9%)- pT0N0 disease in 39 patients and pTmic in 9 patients. When comparing tumor responses between the two groups, SIB group showed excellent results. Toxicity in both arms was the same: leucopoenia - neutropenia, gastro-intestinal toxicities, skin toxicity and another genitourinary complications. Conclusion The regimen, used in this study, allowed to achieve higher complete and near-complete response rate in SIB arm, despite the advanced stage of disease, without increased risk of radiation induced severe acute toxicities.