Overall survival (OS) was the time from the date of randomization to the date of death from any cause. If no death was reported for a participant before the cut-off date for OS analysis, OS was censored at the last date at which the participant was alive. The median OS was calculated based on Kaplan-Meier estimates and corresponding 95% confidence interval (CI) was calculated using the method provided by Brookmeyer and Crowley.

Intent-to-Treat (ITT) population defined as all randomized patients irrespective of whether they received treatment or not.

PFS was the time from randomization to disease progression, or death, whatever occurred first. Progression criteria was met by analysis of target and non-target lesions as defined by Response Evaluation Criteria in Solid Tumors (RECIST) Version 1.1 criteria. Progressive Disease (PD) is defined as at least a 20% increase in the sum of the diameters of target lesions, taking as reference the smallest sum of the diameters while on study or the appearance of one or more new lesions; an increase of at least 5mm as a total sum. Lymph nodes identified as target lesions (≥ 15 mm diameter in short axis) will be followed and reported by changes in diameter of short axis; or the unequivocal progression of a non-target lesion defined as an increase in the overall disease burden based on the change in non-measurable disease that is comparable in scope to the increase required to declare PD for measurable disease; Two or more new bone lesions as detected by bone scan

Based on the Intent to treat population (ITT), defined as all randomized patients irrespective of whether they received treatment or not.

Objective response (OR) is defined as having complete response (CR) or partial response (PR) as best overall response based on RECIST Criteria 1.1 and defines a CR = Disappearance of all target lesions except lymph nodes (LN); LN must have a decrease in the short axis to <10mm; PR = 30% decrease in sum of diameters of target lesions taking as reference the baseline sum diameters; Progressed Disease (PD) = 20% increase in sum of diameters of target lesions taking as a reference the smallest sum of diameters and an absolute increase of ≥5 mm; the appearance of ≥1 new lesions; Stable Disease (SD)= Neither shrinkage to qualify for PR nor increase to qualify for PD taking the smallest sum diameters on study as reference. For non-target lesions a CR = Disappearance of all non-target lesions and all LN must be non-pathological in size <10 mm; Non-CR/Non PD: persistence of one or more non-target lesions; PD = unequivocal progression of existing non-target lesions or appearance of new ones

Based on the ITT population

A TEAE is defined as any AE occurring or worsening on or after the first dose of study drug and within 28 days after the last dose of study drug. A TESAE is defined as any serious adverse event (SAE) occurring or worsening on or after the first dose of study drug and within 28 days after the last dose of study drug. Safety and severity was assessed according to the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI CTCAE) version 4.0; Severity of AEs were graded (including second primary malignancies) as Grade 1- Mild; Grade 2- Moderate; Grade 3- Severe; Grade 4- Life-threatening; Grade 5-Fatal;

The Safety Population is defined as all randomized participants who receive at least one dose of the study treatment (lenalidomide/placebo, Docetaxel, or Prednisone).

Percentage of Participants Who Received Post-Study Therapies for advanced Prostate Cancer.

The Safety Population is defined as all randomized participants who receive at least one dose of the study treatment (lenalidomide/placebo, Docetaxel, or Prednisone).

Second primary malignancies were monitored as events of interest and reported as serious adverse events throughout the course of the trial.

The Safety Population is defined as all randomized participants who receive at least one dose of the study treatment lenalidomide/placebo, Docetaxel, or Prednisone).

Time of Onset of Secondary Primary Malignancies was considered an event of interest

The Safety Population is defined as all randomized participants who receive at least one dose of the study treatment (lenalidomide/placebo, Docetaxel, or Prednisone).