538PPlanned organ preservation for T2 T3 M0 rectal adenocarcinoma: A possible option using chemoradiotherapy (CRT) and contact X-ray brachytherapy (CXB). A French multicenter study

Background Standard treatment for T2-3 M0 rectal adenocarcinoma is rectal resection (TME) often combined with neoadjuvant CRT. If a clinical complete response (cCR) is achieved a “watch and wait” (or local excision) is a possible option to improve quality of life. The Lyon R96-02 phase III trial has demonstrated that adding a CXB boost to CRT was able to increase safely the chance of cCR (1). Since the manufacture in 2010 of the PapillonTM CXB machine, this strategy has seen a renaissance. Methods Between 2003 and 2016, 74 patients M0 have been treated in 3 French centres (Lyon, Mâcon, Nice). Median age was 74 years. Classification was done using MRI and/or Endorectal ultrasound. T2: 45, T3: 29. CRT was: CAP 50 (capecitabine: 800 mg/m2 BID + RT: 50 Gy/ 25 fr/5 weeks). CXB delivered a local boost of 90-110 Gy in3-4 fractions over 4-6 weeks either before or after CRT. The boost was given first if T Results Out of 74 patients with a median follow-up time of 40 months, the cCR rate at 6 months (after treatment initiation) was 95%. The 3-year local recurrence rate and specific cancer survival were respectively 10% and 88%. Organ preservation was seen in 95% with a good bowel function in 90% of cases. Among 6 patients with local recurrence none was seen for polypoid T2T3a Conclusions A possible option for T2 T3 a-b References: 1- Gerard JP et al. J Clin Oncol. 2004 Jun 15;22(12):2404-9. 2- Gerard JP et al. Eur J Cancer. 2019 Feb; 108:1-16. Legal entity responsible for the study The authors. Funding Has not received any funding. Disclosure J. Gerard: Advisory / Consultancy, None: Ariane Medical Systems. All other authors have declared no conflicts of interest.