1810
A 40-year-old man with relapsing-remitting multiple sclerosis (MS) developed primary central nervous system lymphoma (PCNSL) after having received 21 doses of natalizumab monotherapy.
 adverse event: developed 
Please tell me event type and its trigger word from given type options. Output format is "type: trigger".  Option: adverse event, potential therapeutic event 
Text: {0} 
Answer:
 adverse event: developed 