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Table 4 Tabulation of the features of the interim analysis for loco-regional recurrence

From: Hypofractionated radiation therapy comparing a standard radiotherapy schedule (over 3 weeks) with a novel 1-week schedule in adjuvant breast cancer: an open-label randomized controlled study (HYPORT-Adjuvant)—study protocol for a multicentre, randomized phase III trial

Analysis

Value

Efficacy

Futility

IA1: 11%

Z

3.47

− 1.48

N: 1184

p (1-sided)

0.0003

0.9318

 Events: 16

HR at bound

0.28

3.47

 Year: 3

P (cross) if HR = 1.63

0.0003

0.07

 

P (cross) if HR = 1

0.0056

0.008

Final

Z

1.96

1.96

N: 2100

p (1-sided)

0.025

0.025

 Events: 140

HR at bound

1.17

1.17

 Year: 10

P (cross) if HR = 1.63

0.025

0.975

 

P (cross) if HR = 1

0.800

0.200

  1. Asymmetric two-sided group sequential design with binding futility bound, 2 analyses, time-to-event outcome with sample size 2100 and 140 events required, 80% power, 2.5% (1-sided) type I error to detect a hazard ratio of 1 with a null hypothesis hazard ratio of 1.63. Enrollment and total study durations are assumed to be 5 and 10 years, respectively. Efficacy bounds derived using a Lan-DeMets O’Brien-Fleming approximation spending function. Futility bounds derived using a Lan-DeMets O’Brien-Fleming approximation spending function. 1A1 11% = 1st interim analysis done when 11% of the local recurrence events have been observed (information fraction)