Correction to: The effect of pre- and post-operative physical activity on recovery after colorectal cancer surgery (PHYSSURG-C): study protocol for a randomised controlled trial

Correction to: Trials (2017) 18:212

https://doi.org/10.1186/s13063-017-1949-9

Following publication of the original article [1], we were notified of two errors in the Methods section.

• In the ”Allocation” section, the sentence:

”To ensure good balance of participant characteristics in each group, randomisation will be stratified with regard to surgical method (laparoscopic versus open), tumour site and pre-operative treatment (colon, rectum with/without radiotherapy), and study centre.” However, study centre was not included in the electronic randomisation system as stratification.

Should instead read:

”To ensure good balance of participant characteristics in each group, randomisation will be stratified with regard to surgical method (laparoscopic versus open) and tumour site and pre-operative treatment (colon, rectum with/without radiotherapy).”

• In the ”Sample size” section, there was a mix of two approaches considered, which is reflected in the fact that we wrote both that we needed 640 evaluable patients and that this would require 640 randomised patients to account for losses to follow-up. We planned to include 538 evaluable patients, which would result in a need to randomize 640 patients to account for patients being lost to evaluation, as found in the first 100 patients and the interim analysis. Initially we included a Bonferroni correction due to second look into the calculation but discarded this since no statistical testing was performed during the interim analysis. We therefore planned to recruit 538 evaluable participants.

Therefore the sentence:

”For true rates of these magnitudes, a difference will be detected with 80% power using a total of 640 patients and a two-sided test with a 2.5% significance level (Bonferroni adjustment for interim look).”

Should instead read:

”For true rates of these magnitudes, a difference will be detected with 80% power using a total of 538 patients and a two-sided test with a 5% significance level.”