You can find full details on S.3187 at http://hdl.loc.gov/loc.uscongress/legislation.112s3187, and you can find the language on breakthrough therapies in the bill by loading the full text of the legislation and reading in Section 902
Here's what it says:
"Title IX: Drug Approval and Patient Access - (Sec. 901) Expresses the sense of Congress that the FDA should apply accelerated approval and fast track provisions to expedite the development and availability of treatments for serious or life-threatening diseases or conditions while maintaining safety and effectiveness standards for such treatments.
(Sec. 902) Requires the Secretary, at the request of a sponsor of a drug, to expedite the development and review of such drug if the drug treats a serious or life-threatening disease or condition and the drug demonstrates substantial improvement over existing therapies (breakthrough therapy). "