Clinical significance of DNA measurements in small cell lung cancer

Background. Little is known about the relationship between DNA histogram data and the clinical course of small cell lung cancer (SCLC). Methods. The ability of tumor nuclear DNA histograms as measured by cytofluorometry to predict chemotherapeutic responsiveness and propensity for metastases was assessed in 36 patients with SCLC. Histograms were classified into four types: A, mono-mode and euploid; B, mono-mode but not euploid (A + B being monoclonal patterns); C, poly-mode; and D, no mode (C + D being polyclonal patterns). The grade was classified into low (DNA content, smaller than 8C) and high (greater than 8C) by dispersion degrees about each type. Results. The relative rate of response to chemotherapy was A (100%) is greater than B (82%) is greater than C (38%) is greater than D (17%) (A and D, P < 0.05; B and D, P <0.01; A + B and C + D, P < 0.01) and closely related to type. Metastasis rates were significantly different between high (81%) and low (7%) grade (P < 0.01) and closely related to grade (sensitivity, 81%; specificity, 93%). Peripheral SCLC had a significantly lower response rate (20%) than did proximal SCLC (65%) (P < 0.01). In DNA histograms, the proportion of C + D (more heterogeneous than A + B) was significantly higher (80%) in peripheral SCLC (P < 0.01). Conclusions. Nuclear DNA measurements may be potentially useful for predicting distant metastases and response to chemotherapy. The heterogeneity and possibility of resistance to chemotherapy of peripheral SCLC may tend to be higher than those of proximal SCLC.