PREDICTING BREAST CANCER RECURRENCE

1 . A method of determining risk of cancer recurrence in a subject afflicted with breast cancer, the method comprising

determining mRNA expression levels of a plurality of genes in a sample of ER+ breast cancer cells from the subject; and

classifying whether the subject has a low or high risk of cancer recurrence based on the analysis of the mRNA expression levels of the plurality of genes at diagnosis of breast cancer disease,

wherein the analysis of the plurality of genes provides a risk of cancer recurrence after receiving approximately five years of adjuvant therapy that is less than about 5% in the low risk group when compared to retrospective ER+ breast cancer patient datasets with greater than five years of outcome, or representative samples thereof, and

wherein the subject has received approximately five years of adjuvant therapy and is disease-free after that therapy.

2 . The method of claim 1 , wherein an intermediate risk category is also classified.

3 . The method of claim 1 , wherein the low risk group comprises more than 50% of ER+ patients.

5 . The method of claim 1 , wherein the low risk group comprises more than 55% of ER+ patients.

6 . The method of claim 1 , wherein the low risk group comprises more than 60% of ER+ patients.

7 . The method of any claim 1 , wherein risk of recurrence after 5 years is determined.

8 . The method of claim 1 , wherein risk of distant recurrence is determined.

9 . The method of claim 1 , wherein risk of local recurrence is determined.

10 . The method of claim 1 , wherein one of the plurality of genes is HoxB13.

11 . The method of claim 1 , wherein one of the plurality of genes is IL17BR.

12 . The method of claim 11 , wherein the ratio of expression levels of HoxB13/IL17BR is determined.

13 . The method of claim 1 , wherein one of the plurality of genes is Bub1B.

14 . The method of claim 1 , wherein at least one of the plurality of genes is selected from CENPA, NEK2, RACGAP1, and RRM2.

15 . The method of claim 1 , wherein expression levels of Bub1B, CENPA, NEK2, RACGAP1, and RRM2 are determined.

16 . The method of claim 15 , wherein the ratio of expression levels of HoxB13/IL17BR (H:I) is also determined.

17 . The method of claim 16 , wherein the expression levels of Bub1B, CENPA, NEK2, RACGAP1, and RRM2 are summed and a coefficient applied to obtain an MGI index, and H:I and MGI are combined as continuous variables into a BCI value.

18 . The method of claim 17 , wherein the BCI is calculated by assessing the individual risk of cancer recurrence as part of a continuous BCI variable, wherein the risk of recurrence increases in a linear relationship with the BCI variable.

19 . A method of determining risk of cancer recurrence in a subject afflicted with breast cancer, the method comprising

determining mRNA expression levels of HoxB13, IL17BR, Bub1B, CENPA, NEK2, RACGAP1, and RRM2 in a sample of ER+ breast cancer cells from the subject;

summing the expression levels to form a Breast Cancer Index (BCI) value where a higher BCI value is correlated with higher risk of cancer recurrence and a lower BCI value is correlated with lower risk of cancer recurrence; and

classifying the sample, based on BCI value, as indicating a low risk or a high risk of cancer recurrence in the subject, with no intermediate risk category.

20 . A method of determining need for extended treatment of a subject afflicted with breast cancer, the method comprising

determining mRNA expression levels of HoxB13, IL17BR, Bub1B, CENPA, NEK2, RACGAP1, and RRM2 in a sample of ER+ breast cancer cells from the subject;

summing the expression levels to form a Breast Cancer Index (BCI) value, where a lower BCI value is correlated with not requiring any additional treatment with an aromatase inhibitor, targeted therapy or endocrine therapy after an initial treatment with an aromatase inhibitor, targeted therapy or endocrine therapy for five years or less; and

classifying the sample, based on the BCI, as indicating the requirement or lack of requirement for additional treatment.