Long-term survival of T1 and T2 lymph node-negative breast cancer patients according to Mitotic Activity Index: a population-based study.

Node-negative breast cancer patients have a relatively good prognosis, but eventually one-third will die of the disease. Thus, prognostic factors to identify the high-risk group among these patients are needed. We retrospectively determined the Mitotic Activity Index (MAI) for a large series of node-negative breast cancer patients (n = 468) with tumours smaller than 5 cm, who only received locoregional treatment. Patients were followed for up to 29 years; crude and relative survival were calculated, both univariate and multivariate. Relative survival differed significantly according to MAI (p = 0.05), the difference occurred in the first 5 years after diagnosis and remained constant thereafter. After adjustment, MAI still significantly affected relative survival (RER, 1.9; 95% CI, 1.1-3.5). Tumour size also increased the risk, but this was not statistically significant (RER, 1.5; 95% CI, 0.8-2.7). Survival of patients with a T1 tumour and MAI < 10 was similar to that for the general population in the first 5 years after diagnosis. In conclusion, MAI significantly predicted long-term survival for T1/T2N0 breast cancer. Adjuvant systemic therapy appears to have little benefit for node-negative breast cancer patients with a T1 tumour, regardless of the MAI. For those with a T2 tumour and a MAI > or = 10 systemic therapy might have reduced mortality. The need for close surveillance of node-negative breast cancer patients with a T1 tumour and MAI < 10 seems limited.

Trends in breast cancer aggressiveness before the introduction of mass screening in southeastern Netherlands 1975-1989.

OBJECTIVE: The increased incidence of breast cancer in the southeastern Netherlands was accompanied by markedly improved relative survival and stable mortality. We investigated whether the average aggressiveness of tumors changed over time in a population-based study, before the introduction of mass screening. METHODS: The mitotic activity index (MAI) was determined retrospectively for 1051 consecutive patients diagnosed with invasive, non-metastatic breast cancer in 1975, 1981, 1988, and 1989. Trends over time, and effects of age, tumor size and lymph node status were examined by univariate and multivariate regressions. RESULTS: Age-adjusted incidence of low MAI tumors changed from 35/100,000 in 1975 to 45/100,000 in 1988-89, an increase of 30% (P = 0.01), the incidence of tumors with a high MAI increased about 20% (P = 0.28), from 25 to 29/100,000. For small tumors (T1) the odds for a high MAI was lower in 1981 (OR: 0.80; 95% CI: 0.37-1.73) and 1988-89 (OR: 0.66; 95% CI: 0.35-1.23) compared to 1975. Among T3 and T4 tumors the odds increased to 2.03 (95% Cl: 0.71-5.86) in 1981 and 2.16 (0.76-6.18) in 1988-89. CONCLUSION: Although the incidence of tumors with low aggressive potential increased, the incidence of high MAI tumors also increased. Stable breast cancer mortality rates in the face of increasing incidence rates during the period 1975-89 cannot be attributed solely to changes in tumor aggressiveness; early diagnosis and better treatment may also have contributed.