ATLANTIS

Study Group

A Multicenter Retrospective Study on Neoadjuvant Radiochemotherapy With or Without RT Dose Intensification in Locally Advanced Rectal Cancer (LARC)


Aim: To evaluate whether radiotherapy dose intensification (boost) improves pathological complete response (pCR) rates in patients with locally advanced rectal cancer (LARC) undergoing neoadjuvant radiochemotherapy (RCHT).


Pathological Complete Response (pCR)

Treatment GrouppCR Rate (%)
With RT Boost26.6%
Without RT Boost17.0%


Patient Cohort

All patients received standard concurrent chemoradiotherapy, followed by total mesorectal excision (TME). Median interval from RCHT to surgery: 10 weeks (IQR: 5–28 weeks)

GroupPatients (n)
Total1028
With RT Boost364
Without RT Boost664

Toxicity Profile

Toxicity TypeWith Boost (%)Without Boost (%)p-Value
Acute GI toxicity (Grade ≥3) 6.0 1.7 p=0.003

pCR by interval between RCHT and surgery

Interval (weeks)Boosted Group (%)Non-Boosted Group (%)
≤5 10.0 10.6
6–7 23.0 20.8
8–10 26.3 19.3
≥11 39.3 20.4

Conclusions

  • RT dose intensification significantly improves pCR, especially in:
    • Patients with more advanced tumors
    • Patients operated on after ≥11 weeks from RCHT
  • Mild increase in acute toxicity observed in the boosted group

Clinical Implications

  • These findings support personalized treatment planning, particularly regarding:
    • Timing of surgery
    • Tumor stage and location
    • Benefit-risk ratio for dose escalation
Rectal Cancer Survival Calculator

Analysis of patients with locally advanced rectal cancer given neoadjuvant radiochemotherapy with or without RT dose intensification: A multicenter retrospective study – ATLANTIS part I
Figure 2

Tumor response after neoadjuvant RCHT stratified by treatment dose (standard dose versus RT boost)

A) pCR by boost level stratified by primary tumor stage in patients operated ≤10. B) pCR by boost level stratified by primary tumor stage in patients operated ≥11