Like ないで ‘without’, ことなく is an expression used in Japanese following verbs that expresses (B) being done ‘without (A)’. However; ことなく is used in more formal situations, and when there is some contrast between (A) and (B). This may appear in one of two ways, which we will discuss in a moment.
ことなく is a mix of こと, and なく, the adverbial form of ない. It will follow the dictionary form of verbs.
The first contrastive use of ことなく illustrates that (A) is something negative, to which (B) should be done as a preventative measure, or was able to be done while avoiding (A).

• 怪我人（けがにん）を出（だ）すことなく、人質（ひとじち）を全員（ぜんいん）救出（きゅうしゅつ）する事（こと）ができたそうです。
  They were able to rescue all the hostages without injuring anyone.
• 遅刻（ちこく）することなく、職場（しょくば）に着（つ）いた。
  I was able to arrive at work without being late.

The second use of ことなく highlights when (A) is something that was or would be wished for, but unfortunately (B) happened without it being realized. In this way, (A) is frequently some kind of unmet desire.

• 犯人（はんにん）が捕（つか）まることなく10年（ねん）が経（た）つ。
  Ten years pass without the culprit being caught.
• 彼（かれ）は社長（しゃちょう）に何（なに）も言（い）うことなく会社（かいしゃ）を辞（や）めた。
  He quit his job without telling the boss.