Tumor location of the lower-inner quadrant is associated with an impaired survival for women with early-stage breast cancer.

BACKGROUND

There is growing evidence that tumors of the inner quadrants (especially the lower-inner quadrant) metastasize more often to the internal mammary chain (IMC). As these metastases are not investigated, patients with lower-inner quadrant tumors have an increased risk of being under-staged and under-treated and may therefore have a higher risk of death from breast cancer.

METHODS

We identified all 1522 women operated for stage I breast cancer between 1984 and 2002 recorded at the population-based Geneva Cancer Registry. We compared breast cancer mortality risk by tumor location with multivariate Cox regression analysis that accounted for all factors linked to tumor location and survival.

RESULTS

Ten-year disease-specific survival was 93% (95%CI: 91-94%). Patients with breast cancer of the lower-inner quadrant (n = 118; 7.8%) had an importantly increased risk of dying of breast cancer compared to women with breast cancer of the upper-outer quadrant (multiadjusted Hazard Ratio: 2.3, 95%CI: 1.1-4.5, P = 0.0206). The over-mortality associated with this quadrant was particularly evident for tumors >10 mm (multiadjusted HR: 3.6, 95%CI: 1.6-7.9, P = 0.0016). There was no increased breast cancer mortality risk for tumors located in other quadrants.

CONCLUSIONS

Tumor location in the lower-inner quadrant is an independent and important prognostic factor of stage I breast cancer. Further research is needed to evaluate if the over-mortality of patients with stage I cancer of the lower-inner quadrant is indeed a result of under-treatment due to undetected IMC metastases. If so, patients with stage I breast cancer of the lower-inner quadrant are good candidates for systematic IMC investigation.