Guideline development is challenging, expensive and labor-intensive. A high-quality guideline with 90 recommendations for breast cancer treatment was developed within 6 months with limited resources in Costa Rica. We describe the experience and propose a process others can use and adapt.The ADAPTE method (using existing guidelines to minimize repeating work that has been done) was used but existing guidelines were not current. The method was extended to use databases that systematically identify, appraise and synthesize evidence for clinical application (DynaMed, EBM Guidelines) to provide current evidence searches and critical appraisal of evidence. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach was used to rate the quality of evidence and the strength of recommendations. Draft recommendations with supporting evidence were provided to panel members for facilitated voting to target panel discussion to areas necessary for reaching consensus.Training panelists in guideline development methodology facilitated rapid consensus development. Extending 'guideline adaptation' to 'evidence database adaptation' was highly effective and efficient. Methods were created to simplify mapping DynaMed evidence ratings to GRADE ratings. Twelve steps are presented to facilitate rapid guideline development and enable further adaptation by others.This is a case report and the RAPADAPTE method was retrospectively derived. Prospective replication and validation will support advances for the guideline development community. If guideline development can be accelerated without compromising validity and relevance of the resulting recommendations this would greatly improve our ability to impact clinical care.