OBJECTIVES: Previous analyses have projected the health and economic impact of Herceptin® (trastuzumab) in HER2-positive (HER2+) breast cancer over the product life cycle in the US and major EU markets from a payer perspective.  The objective of this analysis is to project the overall product life cycle cost-effectiveness of trastuzumab in HER2+ breast cancer treatment in Portugal, a relatively small (10.6 million inhabitants), lower income EU country, considering the societal perspective. METHODS: Using a product life cycle modeling approach, the projected life cycle (“dynamic”) incremental cost-utility ratio (ICUR) was estimated for the period 2000 to 2020.  The model combines projected “static” ICURs for trastuzumab in early (eBC) and metastatic (mBC) HER2+ BC based on the literature with epidemiological projections of annual HER2+ BC disease incidence and the utilization of trastuzumab in Portugal over this 21-year period.   The major societal saving is reduced work loss for women with eBC who receive trastuzumab.  The dynamic model considers both a payer and societal perspective over a lifetime horizon.  All costs (in 2012 Euros) and outcomes are discounted at 3.0% to the year 2000. RESULTS: The model projects that over the 21-year period, 10,900 women would receive trastuzumab treatment for eBC, and 5,200 women for mBC.   Given the respective ICURs from a payer perspective for eBC  (11,000€ per quality adjusted life year (QALY)) and for mBC  (43,000€ per QALY), the overall dynamic ICUR is approximately 15,000€ per QALY from payer perspective.  Taking a societal perspective, this is projected to be reduced by at least 15%. CONCLUSIONS: Taking a dynamic—and societal—life cycle perspective, in the case of Portugal, over 16,000 QALYs are projected to be gained through the year 2020 at a very favorable ICUR of less than 13,000€ per QALY. Viewed over the product life cycle,  trastuzumab for breast cancer would be considered cost-effective in Portugal.