Long-term clinical outcomes from the groundbreaking Trial Assigning Individualized Options for Treatment (Rx) or TAILORx trial continue to show that most women with early breast cancer can safely forego chemotherapy. The analysis also provides clinicians with new data to inform personalised treatment recommendations for women.

TAILORx used a molecular test that assesses the expression of 21 genes associated with breast cancer recurrence (on a scale of 0-100).

After 12 years of follow-up (median exceeding 10 years), the trial continues to show no benefit from chemotherapy in the overall trial population, whose average age was 56 years, of whom 69% were older than 50. As in the original analysis, the subgroup of younger women (</=50 years) with a score of 21-25 or 16-25 and high clinical risk, who accounted for 7% of the trial population, derived some chemotherapy benefit that persists out to 12 years.

The longer follow-up reveals unexpected information about late recurrences:

For women with a score up to 25, although recurrence rates were very low on average at less than 1% per year, there were more late recurrences beyond 5 years than earlier.

Although distant recurrence rates remained low and overall survival rates remained high for women with a score up to 25 when treated with endocrine therapy alone, there was an increasing divergence between rates of distant recurrence and invasive disease-free survival. This finding indicates that the new development of second primary cancers dominated this population.

Distant recurrence rates remained high for those with a score of 26-100 despite the use of chemotherapy plus endocrine therapy.

There was also a higher risk of early recurrence in Black women:

Racial disparities for Black women were associated with early recurrence within the first 5 years of diagnosis, but not late recurrence. The disparity could not be explained by inequities in social determinants of health or by stopping anti-hormonal endocrine therapy early. The finding adds to a growing body of evidence suggesting that biological factors may contribute to the body developing resistance to endocrine therapy.

Source: Mount Sinai Health System