Evaluation of a tetrazolium-based semiautomated colorimetric assay: assessment of chemosensitivity testing.

Drug sensitivity assays were performed using a variation of a colorimetric [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)] assay on V79, CHO-AuxB1, CHRC5, NCI-H460, and NCI-H249 cell lines following optimization of experimental conditions for each cell line. Results from this assay were compared with data assimilated simultaneously by clonogenic assay and by dye exclusion assay. Good correlation was observed using the CHO-AuxB1 cell line and the pleiotropic drug-resistant mutant CHRC5, with similar degrees of relative resistance observed with both the MTT and clonogenic assays. Good correlation was observed between the clonogenic and MTT assays for 1-h drug exposures, although the MTT assay was more sensitive to vinblastine. In general, the clonogenic assay was more sensitive when continuous drug exposures were utilized, although this was primarily related to the increased drug exposure time. While the use of the MTT assay in drug sensitivity testing of primary tumor samples is limited, since contaminating normal cells may also reduce the tetrazolium, the MTT assay can be semiautomated, and therefore it offers a valid, simple method of assessing chemosensitivity in established cell lines.

Evaluation of a tetrazolium-based semiautomated colorimetric assay: assessment of radiosensitivity.

Radiation survival curves were generated for V79 Chinese hamster and two human lung cancer cell lines (NCI-H460 and NCI-H249) with doubling times of 10, 20, and 85 h, respectively, using a standard clonogenic assay, a dye exclusion assay, and a semiautomated colorimetric assay utilizing a tetrazolium salt, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenylformazan bromide. Comparable results for D0 and extrapolation number (n) were observed for all assays in the lines with doubling times of 10 and 20 h. In these instances the tumor cell lines had undergone seven or more doublings after radiation. For the tumor line (H249) with an 80-h doubling time the D0S were comparable between the assays while the extrapolation number was increased in the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenylformazan bromide assay, a result probably related to the lower number of doublings (less than 4) after radiation. We then tested the ability of the assays to detect radiation protection and sensitization using known agents. We found that cysteamine treatment resulted in radioprotection (by a factor of 8 at 8 Gy) while 5-bromo-2-deoxyuridine incorporation caused enhancement of radiation sensitivity in all three assays. We conclude that, while optimal conditions for each cell line (cell number plated and doubling time) must be established, using characterized tumor cell lines, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenylformazan bromide assay could be automated and thus be of great value in screening large numbers of potential radiosensitizers or protectors.

Abdominal computed tomography in small cell lung cancer: assessment of extent of disease and response to therapy.

Abdominal computed tomography (CT) was performed as part of the initial staging evaluation in 77 patients with small cell carcinoma (SCC) of the lung. CT scans revealed mass lesions in 26 patients (34%). Abnormalities were confined to the liver in 15 patients and to retroperitoneal structures (lymph nodes, adrenal glands, psoas muscle region masses) in eight, and occurred in both areas in three. However, only three of 29 patients otherwise staged as having limited disease (confined to one hemithorax and regional nodes) had evidence of abdominal metastases on CT scan. Most (23/26) positive studies were in patients already known to have more extensive tumor dissemination. In 71 patients with pathologic confirmation of liver status, CT had a sensitivity of 63%, specificity of 91%, and overall accuracy of 85% in assessing the liver. Comparison of radionuclide liver scan findings with hepatic biopsies gave similar results. During therapy, 65 follow-up CT scans were obtained in 46 patients. Scan abnormalities improved or disappeared in 11/12 cases with tumor response documented in other ways, appeared or worsened in 5/13 cases of tumor progression that was diagnosed by other tests, and only rarely (2/65 scans) improved at the time of documented tumor progression, or vice versa. In only three patients, however, did CT scan provide the sole site of evaluable disease during treatment or detect either the only area of residual disease in a patient in otherwise complete remission or the initial evidence of tumor progression. Although abdominal CT scans in SCC can demonstrate metastatic dissemination not evaluable by other means, they provide relatively little therapeutically relevant information beyond that obtained with standard staging procedures.

Small cell lung cancer: radionuclide bone scans for assessment of tumor extent and response.

Radionuclide bone scans were performed before and during combination chemotherapy in 119 systematically staged patients with small cell carcinoma of the lung. Before therapy, 49 patients (41%) had positive scans. Scan positivity was significantly associated with the presence of metastatic tumor in the bone marrow, positive skeletal radiographs, and elevated serum alkaline phosphatase levels. Nonosseous distant metastases were significantly more likely to be detected as the number of areas of focal abnormalities on bone scan increased. The survival of patients with documented distant metastases in bone and nonosseous sites was significantly inferior to the survival of patients with limited disease, isolated osseous extensive disease, and extensive disease occurring only in nonbony sites. Of 36 patients with initially abnormal scans and tumor regression documented by other methods, scan findings improved in 24 (67%). In 26 (36%) of 72 scans in patients demonstrating disease progression in extraosseous sites, new areas of increased radionuclide uptake appeared. Improvement or worsening in follow-up scans was associated with nonbony tumor response or progression, respectively, 70% of the time. Serial bone scans provide reasonably accurate staging and prognostic information in patients with small cell lung cancer, although they are probably not sufficiently reliable to be used as the sole parameter in therapeutic decision-making.