Clinical Usefulness of the Histoculture Drug Response Assay for Breast Cancer.

The histoculture drug response assay (HDRA) was used to compare drug sensitivity of recurrent and primary breast cancer in vitro as well as in the clinic. The HDRA utilizes 3-dimensional culture of human tumors on Gelfoam®. The evaluation rate was 98.8%. The HDRA mean inhibition rate of primary tumors vs. recurrent tumors was, respectively, 57.9% and 38.6% for doxorubicin (DOX); 59.9% and 42.8% for mitomycin C (MMC); 49.0% and 33.4% for 5-fluorouracil (5-FU); and 34.5% and 16.0% for cisplatinum (CDDP). The recurrent cases were pretreated clinically with CAF (cyclophosphamide [CTX], DOX, and 5-FU), CEF (CTX, epirubicin [EPN], and 5-FU), or CMF (CTX, methotrexate [MTX], and 5-FU). 64.7% of the recurrent cases were resistant to all four agents tested compared to 27% of the primary cases. Only 5.9% of the recurrent cases were sensitive to three or more agents as opposed to 18% of the primary cases. The correlation of the HDRA results to clinical outcome in another breast-cancer study was 80.0% with 15 cases evaluated consisting of five true positives, three false positives, seven true negatives, and no false negatives. HDRA was also performed on surgical specimens of primary tumor and axillary lymph node metastasis from each of 30 breast cancer patients. The lymph-node metastases were more resistant than the primary tumor for DOX, 5-FU, and MMC, but not for CDDP. The data suggest that both primary tumor and metastases from individual patients should be tested in the HDRA to enhance clinical efficacy of chemotherapy. There also was a lack of correlation with breast cancer subtype and drug response in the HDRA, further suggesting the importance of individualized treatment for breast cancer patients afforded by the HDRA.