How many {cause of death} are to/by {breast cancer} ?
How many deaths does breast cancer cause?
SELECT (COUNT(?sub) AS ?value ) { ?sub wdt:P509 wd:Q128581 }
SELECT (COUNT(?sub) AS ?subs ) {
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#subject> ?sub .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#predicate> <http://www.wikidata.org/entity/P509> .
?statement <http://www.w3.org/1999/02/22-rdf-syntax-ns#object> http://wikidata.dbpedia.org/resource/Q128581 .
} 

Breast cancer is the cause of how many deaths?