Correlation between in vitro labeling indices (LIs) and tumor regression following radiotherapy

Abstract

Abstract The in vitro tritiated thymidine labeling indices (LIs) of fine-needle aspirates obtained from metastatic lymph nodes and subcutaneous nodules of 38 patients before, during and after radiotherapy, was determined in order to study the relationship between the change in the LIs and the response to radiotherapy. The squamous cell carcinomas had pre-radiotherapy LIs of 0.7–28.6% (geometric mean 4.8%) and post-radiotherapy LIs of 0.0–2.6% (geometric mean 1.5%). The adenocarcinomas had pre-radiotherapy (RT) LIs of 0.9–23.7% (geometric mean 6.2%) and post-RT LIs of 0.0–19.4% (geometric mean 2.6%). Whenever post-RT LIs showed at least two-thirds decrease from the pre-RT levels, a favorable response (a decrease in diameter of the tumor of 50% or more) was observed. This technique may be useful in determining the radiation response as well as the dose response curve of accessible human tumors.