A biotech ETF with a tilt to small-cap stocks continued its strong breakout Wednesday with a nearly 3% rally one day before an expected Supreme Court ruling on the constitutionality of healthcare reform.

SPDR S&P Biotech ETF (NYSEArca: XBI) was up 2.6% in afternoon trading Wednesday on heavy volume.

XBI tracks an equal-weighted index rather than weighting stocks by market capitalization. Therefore, it allocates more to smaller companies compared with its large-cap biotech sector peers. [Choosing the Right Biotech ETF Exposure]

The biotech ETF was up 30.3% year to date as of June 26 while the S&P 500 gained 5.6%, according to Morningstar. [Biotech ETFs in ‘Stealth’ Bull Market]

XBI is trading at an all-time high.

Showing Page 1 of 2