Correlation between Dose and Tumor Response in the Radiotherapy of Lung Cancer of Various Histological Types

Correlation between dose and tumor response by cell types wasdetermined in 50 patients with lung cancer in order to predictthe possibility of further tumor regression. The TDF (time-dose-fractionation)concept was used as dose factor. The radiation source was a cobalt-60 -ray or linear accelerator10 MV X-ray. As a routine regime a fraction dose of 2 Gy fivetimes per week was given to 39 of the 50 patients, but a doseof 2 Gy three times per week or of 1.5 Gy five times per weekwas given to seven and four patients, respectively. Radiation response was the best in small cell carcinoma andbetter in adenocarcinoma than in squamous cell carcinoma, showinga tumor regression rate of 50% or more in 90%, 80% and 58% ofthe patients, respectively. The correlation between tumor regression rate and TDF valueswas good in squamous cell carcinoma (r=0.73) and small cellcarcinoma (r=- 0.72), but poor in adenocarcinoma (r=- 0.10).These results suggest that in squamous cell carcinoma improvementof tumor regression can be expected by increasing TDF values,and in adenocarcinoma and small cell carcinoma the optimal TDFvalues are about J00 and 60 to 80, respectively.