Predictive value of regression rates following chemotherapy of small cell carcinoma of the lung

Tumor volumes measured at the time of initial therapy, during the 28 days following treatment, and following subsequent courses of therapy for 29 patients with small cell carcinoma of the lung were determined from serially measurable roentgenographic lesions. Tumor-halving times were calculated following initial therapy, and the proportions of pretreatment tumor volumes were evaluated within 28 days after initial therapy for 26 patients. Pretreatment tumor volumes ranged from 22.5 to 485 cu cm, with a median of 87 cu cm, a log mean of 83 cu cm, and a linear mean of 113 cu cm. The tumor-halving times ranged from 4 to 86 days, with a median of 12 days, a log mean of 12 days, and a linear mean of 16 days. The reduction of tumor volume expressed as a proportion of pretreatment volume following therapy ranged between 0.02 and 0.65, with a median value of 0.22, a log mean of 0.18, and a linear mean of 0.26. Using the linear mean of 0.26 as a discriminant for survival analysis, patients with ⋖0.26 had a median duration of survival of 12 months, which was significantly longer (p = 0.035) than the median survival of 8 months for patients with ⋗0.26. Tumor-halving time of 16 days was also able to separate the survival durations of 12 months of those ⋖16 days compared to 8 months for ⋗16 days (p = 0.0429). Tumor regression rate, determined from two consecutive tumor volume measurements, was correlated with the tumor volume (r = 0.677; p ⋖ 0.0001); and volume dependency of the tumor regression rate, as specified in Gompertzian kinetics, was demonstrated.