Correlation of in vitro drug-sensitivity testing results with response to chemotherapy and survival in extensive-stage small cell lung cancer: a prospective clinical trial

Abstract

We devised a novel clinical protocol for extensive-stage small cell lung cancer (SCLC), selecting chemotherapy whenever possible on the basis of in vitro drug-sensitivity testing (DST) of individual patients' tumor specimens. Most of the specimens were obtained from metastatic sites during routine staging procedures. Increase of tumor cell number by culture in selective media usually was required before DST could be performed. We used the Weisenthal dye exclusion assay to place the seven drugs in rank order and to select the in vitro best regimen (IVBR), a three-drug combination of proved efficacy in SCLC. After initial staging and specimen acquisition, patients received etoposide and cisplatin (primary therapy) and were restaged after 12 weeks. Patients with partial or no responses and those relapsing after a complete response to primary therapy were switched to the IVBR if DST data were available. If DST data were unavailable, an empiric combination, vincristine-doxorubicin-cyclophosphamide, was administered as secondary therapy. Tumor-containing specimens were collected from 60 of the 80 patients (75%). One or more cell lines were established from 28 patients, and DST data were available from 26 patients (33% of total). Several parameters of in vitro drug sensitivity were significantly associated [two-sided P (P2) less than .05] with clinical response to primary therapy and also with response to the IVBR and were marginally associated with length of survival (.07 less than or equal to P2 less than or equal to .08). Sixteen patients (23%) received their IVBR as secondary therapy, and four of these (25%) attained a complete response, compared with three of 43 (7%) who received an empiric regimen (P2 = .16). We concluded that (a) selection of individualized chemotherapy is labor intensive but feasible in extensive-stage SCLC; (b) DST data are associated with clinical response to primary therapy and to secondary therapy with an IVBR; and (c) further observations will be required if we are to determine whether there is a modest therapeutic benefit to administering the IVBR as a secondary therapy.