DIFFERENTIAL SENSITIVITY OF 3 SUBLINES OF THE RAT DUNNING PROSTATE TUMOR SYSTEM R3327 TO RADIATION AND OR LOCAL TUMOR HYPERTHERMIA/

To better understand the relationship of the growth characteristics of tumor tissues and their response to ionizing radiation alone and in c ombination with local tumor hyperthermia, we compared three different tumor sublines of the Dunning rat prostate carcinoma R3327. This repor t includes results obtained with the anaplastic AT1 subline (volume do ubling time 5.2 days), the moderately differentiated mucin-secreting H I subline (volume doubling time about 9 days) and the well-differentia ted, hormone-dependent H subline (volume doubling time about 17 days). The effects of single doses of photons (10 to 40 Gy) with and without local tumor hyperthermia (35 min immersion at 43.5 degrees C) were qu antified by growth delay. The time to reach five times the volume at t he time of treatment after 30 Gy alone was found to be 56.0, 134.9 and 184.0 days for the R3327-AT1, HI and H tumors, respectively. The R332 7-H tumor was more radiosensitive than the AT1 or HI subline. Five of nine R3327-H tumors were controlled locally with a single dose of phot ons (40 Gy). Local tumor hyperthermia alone induced growth delay in bo th differentiated tumors, while the anaplastic tumor subline did not r espond. Combined treatment modalities with heat applied directly after irradiation revealed isoeffective thermal enhancement ratios for 30 G y which decreased from 1.59 for the AT1 tumor and 1.42 for the HI tumo r to 1.23 in the well-differentiated subline R3327-H. (C) 1998 by Radi ation Research Society.