ESTRO 2020 Abstract book

S632 ESTRO 2020

The intensification of the neoadjuvant radiotherapy for LARC seems to produce a major pathological response in T3 tumors. The radiation dose intensification is not correlated with the rate of radiation toxicity, surgical complications and complexity. PO-1107 Impact of fractionation on the treatment of squamous cell anal cancer: a dual-institution experience M. Vernaleone 1 , P. Bonomo 2 , B. Meduri 1 , G. Caramia 2 , G. Aluisio 1 , L. Visani 2 , I. Desideri 2 , C. Becherini 2 , E. D'Angelo 1 , L. Livi 3 , F. Lohr 4 1 Azienda Ospedaliero-Universitaria di Modena, Oncology Department - Radiation Oncology Unit, Modena, Italy ; 2 Azienda Ospedaliero-Universitaria Careggi, Radioterapia Oncologica, Firenze, Italy ; 3 Azienda Ospedaliero- Universitaria Careggi- University of Florence, Radioterapia Oncologica, Firenze, Italy ; 4 Università degli Studi di Modena e Reggio-Emilia, Oncology Department - Radiation Oncology Unit, Modena, Italy Purpose or Objective It is known that a prolonged overall treatment time (OTT) has a detrimental effect on outcome for non-metastatic squamous cell anal cancer (SCAC) patients. Aim of our work was to evaluate the impact of an accelerated radiotherapy regimen (AF) on tolerability and efficacy in comparison with conventional fractionation (CF). Material and Methods Between March 2014 and June 2018, patients affected by non-metastatic SCAC treated with Tomotherapy in two different institutions were considered for our study. A frequency-matched cohort analysis was performed to balance patients’ characteristics between the two groups (AF and CF): median age, disease stage and administration of concurrent chemotherapy were the considered variables. Most used treatment schedules for the two groups were 55 Gy/2.2 Gy/fx vs 54 Gy/2 Gy/fx to high risk PTV, 45 Gy/1.8 Gy/fx vs 45.9/1.7 Gy/fr to low risk PTV in 25 and 27 fractions in the AF and CF cohorts, respectively. Acute toxicity was scored according to NCI – CTCAE v. 4.03. Time to progression (TTP) and overall survival (OS) were calculated from the end of treatment to the date of first local or distant recurrence and to the date of death from any cause, respectively. Moreover, time to colostomy (TTC) was calculated, as the time from the end of treatment to the salvage colostomy. Results Overall, 94 patients were included; 46 (49%) and 48 (51%) received a CF and AF radiotherapy treatment, respectively. Patients’ characteristics were well matched between the two cohorts: the median age was 66,1 and 66,5 years, and the incidence of stage III was 56,5% and 52% (TNM AJCC 7th ed.) in CF and AF groups, respectively; while, concurrent chemotherapy was prescribed to 86,7% of CF patient and 70,8% of AF ones, with mytomicin C-5FU as the most common regimen. The rate of non-hematologic acute toxicity ≥ G2 (radiation dermatitis, diarrhea and cystitis) were 73% vs 63%, 18% vs 31%, and 11% vs 2% in CF and AF cohorts, respectively. In terms of overall non-hematologic acute toxicity, the ≥ G2 rate was 80% and 69%, respectively. For all safety outcomes, no statistically significant difference could be found between the two groups. With a median follow-up of 30 months, 2-year TTP was 76,3% vs 81,7%, while OS was 89,6% vs 93,6% in CF and AF cohorts, respectively, with no statistically significative differences. Moreover, 2-year TTC was 86% for CF vs 95,8% for AF (p=0,24). Conclusion This preliminary analysis of our dual-institution experience does not show any statistically significant differences on safety nor efficacy between a mild accelerated hypofractionation and a conventional regimen. A longer FUP is needed to confirm the data and to evaluate any late toxicity.

PDR-BT boost to the residual tumor, with intention to deliver a minimal total dose of 60 Gy. Brachytherapy implantation was performed according to the Paris system, only one plane implant being used. Patients outcome was examined with focus on local control and morbidity. Results A total of 42 patients were identified: 24, 13, and 5 with stages I, II, and III tumors, respectively. The greatest dimension of residual tumor at the time of brachytherapy procedure was 8.8 mm (range: 0-30 mm). Median BT dose was 20 Gy (range: 10-30 Gy), delivered through a median number of 48 hourly pulses (range: 20-80 pulses). Median dose per pulse was 42 cGy (range: 37.5-50 cGy). Median treated volume was 9.7 cm 3 (range: 4.5-34.28 cm 3 ). Median over dosage volume (V 200% ) was 1.7cm 3 (range 0.4- 7.3 cm 3 ). The median number of implanted needles was 3 (range: 2–4). With median follow-up of 60.4 months (range: 5.4-127.4 months), a total of five patients (12%) experienced tumor relapse, including local relapse in three patients (7.1%). Thirty-eight (90%) were alive at last follow-up. No Grade 3 or more acute toxicity was reported. Out of 40 patients with more than 6 months follow-up, only one patient experienced grade 3+ delayed toxicity (fecal incontinence). None patient required surgery for toxicity. Conclusion With almost 5 years median follow-up, this study confirms that an approach based on PDR-BT treating the tumor residuum is effective and safe in this indication for selected patients with mainly Stage I tumors. Local control rate and toxicity were in the range of what was seen with continuous low-dose-rate brachytherapy. Morbidity profile was favorable, possibly as a consequence of patient selection and technique used. PO-1106 Dose intensification in locally advanced rectal cancer: a prospective observational study E. BertocchI 1 , L. Nicosia 2 , R. Mazzola 2 , G. Barugola 1 , F. Ricchetti 2 , P. Dell'Abate 1 , G. Ruffo 1 , F. Alongi 2 1 IRCCS - Ospedale Sacro Cuore Don Calabria, Department of Surgery, Negrar, Italy ; 2 IRCCS - Ospedale Sacro Cuore Don Calabria, Department of Advanced Radiation Oncology, Negrar, Italy Purpose or Objective The potential role of neoadjuvant radiation dose intensification in locally advanced rectal cancer (LARC) is still largely debated. In the present study, a comparative analysis between radiation dose intensification and conventional fractionation was performed. Material and Methods In the current prospective observational study, 56 patients diagnosed with LARC were enrolled between January 2013 and December 2016. More specifically, 25 patients underwent pre-operative conventional radiation dose (i.e. 50.4 Gy in 28 fractions here defined as SDR – group 1) whereas 31 patients were candidate to radiation dose intensification (i.e. 60 Gy in 30 fractions here defined as RDI - group 2). The primary end-point was the complete pathological response (pCR) rate. Secondary end-points were post-operative complications and ChT-RT related toxicity. Results No statistical significance was observed in pCR rate (i.e. 20.8% in SDR group and 22.6% in RDI, p=0.342). Of contrast, the RDI group showed a significantly higher primary tumor downstaging in case of T3 tumors comparing to SDR group (p=0.049). All patients had R0 margins. No surgical related death was recorded. No statistically significanct difference was observed regarding surgical complications between SDR and RDI (28% versus 41.9%, respectively; p=0.40). Not surgical complications were higher in RDI group (p<0.05). Acute genito-urinary toxicity was significantly higher in RDI group (p=0.015). Conclusion