In vitro chemoresponse in metachronous pairs of gyneclologic cancers.

Background: While most gynecologic cancers respond to first-line cytotoxic chemotherapy, treatment of recurrent disease is frequently associated with acquired drug resistance. In order to find an in vitro surrogate of this clinical phenomenon, a tumor chemoresponse assay was studied.

Methods/materials: Patients who had tissue submitted for repeated chemoresponse testing were identified through a retrospective search. Sixty-three patients met inclusion criteria (chemoresponse testing completed at primary diagnosis and upon recurrence of disease and assays completed ≥90 days apart). The Wilcoxon signed-rank test was used to compare chemoresponse, represented as a response index (RI), between primary and recurrent measurements. In a secondary analysis, response was categorized and coded as Responsive = 3, Intermediately Responsive = 2 and Non-Responsive = 1, and the paired t-test was used to compare chemoresponse between primary and recurrent measurement.

Results: Median time between primary and recurrent tumor testing was 309 days (IQR 208-422). Drugs tested included carboplatin, cisplatin, docetaxel, doxorubicin, gemcitabine, paclitaxel, topotecan, and combination carboplatin/gemcitabine and carboplatin/paclitaxel. There were no differences in chemoresponse between primary and recurrent measurement when chemoresponse was represented by RI scores; although a trend toward increased resistance to paclitaxel upon recurrence was noted. When chemoresponse was analyzed as a continuous variable corresponding to categorized response, a significant shift toward increased resistance to paclitaxel at recurrence, and a marginally significant trend toward increased resistance to carboplatin at recurrence, were observed.

Conclusions: We observed a trend toward increased chemoresistance at recurrence for paclitaxel, and a marginally significant trend toward increased chemoresistance to carboplatin, but no change in chemoresponsiveness between primary diagnosis and recurrence of disease for other common chemotherapy drugs, including common second-line agents such as doxorubicin, gemcitabine, and topotecan.