Adverse events

Participants received 4 capsules of ibrutinib-matching Placebo administered orally once daily continuously starting on Day 1, Cycle 1 until disease progression, or unacceptable toxicity, or study end, whichever occurred first. All participants also received a maximum of 6 cycles of BR background therapy (bendamustine hydrochloride 90 milligrams per meter square \[mg/m\^2\] intravenous \[IV\] infusion on Days 1 and 2 of each cycle and rituximab 375 mg/m\^2 IV infusion on Day 1 of each cycle), unless disease progression or unacceptable toxicity prior to Cycle 6. Participants with a complete response (CR) or partial response (PR) continued to receive background therapy with rituximab maintenance (375 mg/m\^2 IV infusion) on Day 1 every second cycle starting at Cycle 8 for a maximum of 12 additional doses unless disease progression or unacceptable toxicity. Each cycle was of 28 days. Participants received treatment A up to 100.1 months. After treatment unblinding at the time of the primary analysis, participants randomized to Treatment A discontinued placebo treatment.

Participants received ibrutinib capsules 560 mg (4\*140 mg capsule) administered orally once daily continuously starting on Day 1, Cycle 1 until disease progression, or unacceptable toxicity, or study end, whichever occurred first. All participants also received a maximum of 6 cycles of BR background therapy (bendamustine hydrochloride 90 mg/m\^2 IV infusion on Days 1 and 2 of each cycle and rituximab 375 mg/m\^2 IV infusion on Day 1 of each cycle), unless disease progression or unacceptable toxicity prior to Cycle 6. Participants with a CR or PR continued to receive background therapy with rituximab maintenance (375 mg/m\^2 IV infusion) on Day 1 every second cycle starting at Cycle 8 for a maximum of 12 additional doses unless disease progression or unacceptable toxicity. Each cycle was of 28 days. Participants received treatment B up to 117.2 months. After treatment unblinding at the time of the primary analysis, participants randomized to Treatment B continued treatment with ibrutinib at the discretion of the investigator.