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Mitotic activity index superior to other breast cancer prediction tools

By Laura Dean

05 January 2011

MedWire News: The mitotic activity index (MAI) is prognostically superior to both Adjuvant! and the Norwegian Breast Cancer Group (NBCG) guidelines when used to predict survival in patients with lymph node (LN)-negative breast cancer younger than 55 years of age, study findings indicate.

In large studies, the MAI - a proliferation marker that selectively assesses the mitotic activity in the periphery of the tumor - has proven to be a robust and reproducible prognostic factor in certain groups of breast cancer patients, explain Jan Baak (Stavanger University Hospital, Norway) and colleagues.

In the present study, Baak and team compared the accuracy of the Adjuvant! online program and the NBCG guidelines with MAI in the prediction of 10-year breast cancer-specific survival (BCSS) among 516 women (age <55 years) with LN-negative breast cancer who did not receive adjuvant systemic therapy.

Patients were considered to have a high risk for death if they had an Adjuvant! score below 95%, a MAI score at or above 3, or were placed in the NBCG 'adjuvant systemic therapy group' rather than the 'no systemic therapy' group (pT1, grade 1, all ages or pT1a-b, grade 2-3, ≥35 years, all node negative and hormone receptor positive).

The 10-year breast cancer-specific death rates were 9%, 5%, and 8% in Adjuvant!, MAI, and NBCG high-risk patients, respectively.

The researchers found that the overall agreement was "fair" between Adjuvant! and MAI and between NBCG and MAI, at a respective 74% and 73%.

High-risk MAI patients had a significantly lower rate of 10-year BCSS than those with low-risk patients, at 71% versus 95% respectively.

Similarly, 10-year BCSS was significantly lower among high-risk Adjuvant! (74% vs 91%) and NBCG (75% vs 92%) patients compared with their low-risk counterparts.

Yet, in a multivariable survival analysis, MAI was the only significant predictor of 10-year BCSS.

When the groups were combined for further analysis, Adjuvant! and NBCG provided no additional prognostic value to MAI, whereas MAI identified 40% and 39% of NBCG and Adjuvant! low-risk patients as high-risk.

"These data strongly suggest that MAI is prognostically superior to both Adjuvant! and NBCG," conclude Baak and co-authors in the Journal of Clinical Oncology.

They add that their findings "call for the inclusion of MAI in studies testing the clinical performance of new prognostic/predictive factors."

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2011

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