Gastrointestinal Cancer

SS 17 - GI 3 - Colon/Rectum/Anus

127 - Preoperative Radiation Therapy With a Simultaneous Integrated Boost Compared to Chemoradiotherapy for cT3-4 Rectal Cancer: A Multicentric Randomized Study.

Monday, October 22
4:15 PM - 4:25 PM
Location: Room 214 C/D

Preoperative Radiation Therapy With a Simultaneous Integrated Boost Compared to Chemoradiotherapy for cT3-4 Rectal Cancer: A Multicentric Randomized Study.
B. Engels1, A. De Paoli2, E. Delmastro3, F. Munoz4, S. Vagge5, D. Norkus6, H. Everaert7, G. Tabaro2, E. Garibaldi3, U. Ricardi4, E. Borsatti2, P. Gabriele3, G. Boz2, E. Dubaere1, M. Mahe8, T. Gevaert1, and M. De Ridder1; 1Radiotherapy Department, UZ Brussel, Vrije Universiteit Brussel, Brussels, Belgium, 2National Cancer Institute, Aviano, Italy, 3IRCC Candiolo, Candiolo, Italy, 4Department of Oncology, University of Torino, Torino, Italy, 5IRCCS San Martino IST National Cancer Research Institute and University, Genoa, Italy, 6National Cancer Institute, Vilnius, Lithuania, 7Department of Nuclear Medicine, UZ Brussel, Vrije Universiteit Brussel, Brussels, Belgium, 8Centre Rene Gauducheau, St. Herblain Cedex 44805, France

Purpose/Objective(s): Preoperative chemoradiotherapy (CRT) has been established as the standard treatment for T3-4 rectal cancer. As an alternative strategy, we reported previously in a phase II study limited toxicity and high local control (LC) using image-guided and intensity-modulated RT (IG-IMRT) with a simultaneous integrated boost (RTSIB) instead of concomitant chemotherapy. The present multicentric randomized trial (NCT01224392) compared this strategy to CRT. Early and late outcome are reported.

Materials/Methods: cT3-4 rectal cancer patients were randomly assigned to receive either preoperative IG-IMRT 46Gy/23 fractions plus capecitabine 825 mg/m2 twice daily (CRT-arm) or IG-IMRT 46Gy/23 fractions with a SIB to the rectal tumor up to a total dose of 55.2 Gy (RTSIB-arm). Surgery was performed 6-8 weeks after completion of preoperative treatment. Adjuvant chemotherapy consisted in both arms of 6 cycles capecitabine 1000mg/m2 twice daily on day 1 to 14, every 3 weeks. Metabolic tumor activity reduction, by measuring the percentage of SUVmax difference on sequential FDG-PET imaging, was the primary short-term endpoint.

Results: A total of 174 patients were randomly assigned to the CRT-arm (n=89) or RTSIB-arm (n=85) between April 2010 and May 2014. Grade 3 acute toxicity was 6% and 4% in the CRT- and RTSIB-arm, respectively. The mean fractional change in SUVmax at 5 weeks after completion of preoperative RT was -55.8% (±24.0%) and -52.9% (±21.6%) for patients in the CRT-arm and RTSIB arm, respectively (p=0.43). There were no significant differences in sphincter preservation (75% vs 68%) and R0 resection rate (98% vs 97%). The pathologic complete response rate (pCR) rate was 24% with CRT compared to 14% with RTSIB (p=0.13). Dworak grade 3-4 rates were comparable between both arms (49% for CRT vs 45% in the RTSIB-arm). Adherence to a full course of adjuvant chemotherapy was low (34% in the CRT-arm and 31% in the RTSIB-arm). After a median follow-up of 48 months, we report a 5-year overall survival (OS) of 76.1% in the CRT-arm vs 74.8% for the RTSIB-arm (p=0.91). There were no differences between treatment arms either for 5-year progression-free survival (PFS) (54.7% for CRT vs 55.4% for RTSIB, p=0.48) and 5-year LC (94.3% for CRT and 93.4% for RTSIB, p=0.42). The absolute incidence of any grade ≥ 3 late gastrointestinal and urinary toxicity was 7% and 5% for CRT whereas 5% and 4% for RTSIB patients, respectively.

Conclusion: The preoperative RTSIB approach was not inferior to CRT in terms of OS, PFS and LC in the current study. Acute and late toxicity did not differ between treatment arms. RTSIB represents a promising alternative to CRT in patients with cardiac comorbidity or other contra-indications for 5-fluorouracil based chemotherapy.

Author Disclosure: B. Engels: None. A. De Paoli: None. E. Delmastro: None. F. Munoz: None. U. Ricardi: President Elect; ESTRO. G. Boz: None. E. Dubaere: None. M. Mahe: None.

Benedikt Engels, MD, PhD

Disclosure:
No relationships to disclose.

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127 - Preoperative Radiation Therapy With a Simultaneous Integrated Boost Compared to Chemoradiotherapy for cT3-4 Rectal Cancer: A Multicentric Randomized Study.



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