THERMAL-TREATMENT PARAMETERS ARE MOST PREDICTIVE OF OUTCOME IN PATIENTS WITH SINGLE TUMOR NODULES PER TREATMENT FIELD IN RECURRENT ADENOCARCINOMA OF THE BREAST

Purpose: In previously reported studies using radiation therapy (XRT) and hyperthermia (HT) for treatment of superficial metastases from ade nocarcinoma of the breast, we have identified several pretreatment and treatment parameters that correlated with rate of initial complete re sponse (ICR) recorded at 3 weeks and duration of local control(DLC). T hese parameters include minimal intratumoral temperature, T-min, and t he temperature exceeded by 90% of the measured intratumoral temperatur es, T-90 Recently, others have shown that thermal dose defined as the cumulative time of isoeffective treatments with T-90 = 43 degrees C (C UM EQ MIN T-90 43) was predictive of complete response in superficial tumors. We have assessed the prognostic value of several formulations of this parameter for both ICR and DLC in a relatively uniform patient population treated with XRT-HT. Methods and Materials: The correspond ing EQ MIN T-90 43 were calculated for 332 HT treatments in 111 HT fie lds in 83 patients who started treatment between October 1982 and May 1992. Each field contained only one measurable superficially located n odular tumor recurrence or metastasis from adenocarcinoma of the breas t that was treated with XRT-HT, had mapped or multiple point temperatu res recorded, and had at least one posttreatment follow-up evaluation. The thermal doses from all treatments delivered to a field were added to obtain the total thermal dose, SUM EQ MIN T-90 43. Logistic and li fe-table multivariate analyses were performed to determine which pretr eatment parameters (including initial T-stage, prior XRT, and tumor vo lume at the time of HT) and treatment parameters (including XRT dose, T-min, T-90, thermal dose, and hormonal therapy) best correlated with ICR and DLC. Results: Of the treatment parameters tested, SUM EQ MIN T -90 43 had the strongest correlation with both ICR (p = 0.0002) and DL C (p = 0.0014). Also, SUM EQ MIN T-90 43 contributed to the best multi variate models predictive of ICR and DLC. Conclusion: For this relativ ely uniform patient population, we have confirmed that SUM EQ MIN T-90 43 is the treatment parameter most strongly correlated with not only response following XRT-HT, but also duration of local control. This fo rmulation of thermal dose should permit prescriptions to be written fo r HT treatments. Prospective trials designed to confirm this thermal d ose relationship are to be encouraged.