antineoplastic vs antitumor

antineoplastic is a noun but antitumor is not a noun.

Word	Noun	Adjective	Verb	Adverb
antineoplastic	Yes	Yes	No	No
antitumor	No	Yes	No	No

As adjectives, antineoplastic and antitumor are synonyms defined as:

Other synonyms of antineoplastic include anticancer, antitumour.

antineoplastic (noun)	antitumor (noun)
any of several drugs that control or kill neoplastic cells; used in chemotherapy to kill cancer cells; all have unpleasant side effects that may include nausea and vomiting and hair loss and suppression of bone marrow function

antineoplastic (adjective)	antitumor (adjective)
used in the treatment of cancer	used in the treatment of cancer