The influence of autologous tumor fibroblasts on the radiosensitivity of squamous cell carcinoma megacolonies.

Purpose: To study the influence of tumor fibroblasts on radiosensitivity and stem cell fraction of tumor cells in squamous cell carcinoma megacolonies by determining colony cure and clonogen survival.

Methods And Materials: Murine squamous cell carcinoma cells (AT478c) grown as flat but multilayered megacolonies were co-cultured with pre-irradiated tumor fibroblasts derived from the same carcinoma, and irradiated with 1, 2, 4, or 8 fractions. Recurrent clones and their growth pattern in situ were recorded.

Regrowth delay analysis of irradiated tumors in the curative dose region.

Purpose: To develop a method to analyze regrowth delay times, including cured tumors.

Methods And Materials: Regrowth delay measured in the in vitro squamous cell carcinoma megacolony system following fractionated irradiation was analyzed using two different approaches. A conventional regrowth delay analysis based on means or medians of dose groups was contrasted with a one-step procedure using the inverse of individual regrowth delay times, where cured tumors are represented by an infinite delay time.