Table 3. Comparison of the traditional NPI with NPI+.

Traditional NPI	NPI+
Applicable to all forms of primary invasive breast cancer	Applicable to all forms of primary invasive breast cancer but initial phase of NPI+ classification categorises into one of seven molecular classes
Applies equal weighting of prognostic factors (histological grade, lymph-node stage and tumour size) to all types of invasive breast cancer without consideration for molecular classes	Second phase of NPI+ classification uses prognostic factors and weighting relevant to each molecular class. Additional prognostic factors such as lymphovascular and invasion progesterone receptor are included in the formulae
Stratifies in terms of expected prognosis	Stratifies effectively in each molecular class identifying patients whose outcome is as expected following standard therapy vs those who have a suboptimal outcome and may benefit from alternative/additional forms of treatment

Abbreviation: NPI+=Nottingham prognostic index plus.