Background: phase III RCT included 912 patients with newly diagnosed, rectal adenocarcinoma, high-risk on pelvic MRI (clinical cT4a/cT4b or extramural vascular invasion or cN2 or involved mesorectal fascia, or enlarged lateral LN) nodes

Arm A: RT 5×5Gy x 8d, then CAPOX x 6 or FOLFOX4 x 9, then TME*
Arm B: RT 1.8Gy x 28fr up to 50.4 Gy or 2.0Gy x 25fr with concomitant capecitabine 825 mg/m2 BID, then TME, then Adjuvant CAPOX x 8 or FOLFOX4 x12

Primary end point: 3-year disease-related treatment failure (DRTF)
mFollow up: 4.6yr

3-yr DRTF: 23.7% vs 30.4%, arm A vs arm B respectively; HR 0.75, 95% CI 0.60–0.95; P=.019
3-yr cumulative probability distant metastases: 20% vs 27%, HR 0.69, 95% CI 0.54-0.90
3-yr locoregional failure:8% vs 6%
pCR: 28% vs 14%

Main adverse events. Most common grade >=3 event during preoperative therapy= diarrhea 18% vs 9% arm A vs arm B. Serious adverse events were similar (34% each group). 52% of the patients did not receive adjuvant chemotherapy as it was not mandatory

Conclusions. Preoperative short course radiotherapy and chemotherapy was associated with reduced disease related treatment failure in comparison to preoperative chemoradiotherapy with or without adjuvant chemotherapy in this study.

*
CAPOX capecitabine 1000 mg/m2 PO BID D 1–14, oxaliplatin 130 mg/m2 IV D1 Q21
FOLFOX4 oxaliplatin 85 mg/m2 IV D1, leucovorin 200 mg/m2 IV D1,2, followed by bolus fluorouracil 400 mg/m2 IV and fluorouracil 600 mg/m2 IV x 22 h on D1 and 2, Q14D

Summarized by Thejus Jayakrishnan, MD

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