When proposed, this model allowed for the understanding of tumour growth, treatment failure, and tumour aggression that occurs during the natural process of tumour formation.

Symptoms may significantly alter the quality of life of affected patients, and brain metastases generally represent overall treatment failure.

The primary outcome was freedom from treatment failure after 16 weeks of therapy; the secondary outcome was attentional dysfunction.

The more treatment failures they have, the less the chance they will respond to subsequent treatments.

In other cases of endodontic treatment failure, a referral to a periodontist or an oral and maxillofacial surgeon for replacement of the tooth with a dental implant may be indicated.