Clinical experience with interstitial thermoradiotherapy for localized implantable pelvic tumors

Twenty-six patients (20 females, 6 males) with localized tumors of the pelvis, including 3 primary advanced (PRIM), 7 persistent (PERS), 10 recurrent (REC), and 6 metastatic (MET) tumors, were treated with a combination of low-dose rate (LDR) iridium 192 interstitial radiotherapy (IRT), interstitial 915 MHz microwave hyperthermia (IHT), and external beam radiotherapy (RT). Histological diagnoses were squamous cell carcinoma in 13 (50%), adenocarcinoma in 12 (46%) and soft tissue sarcoma in 1 (4%) lesion. Tumor sites were cervix in 8 (31%), colorectum in 6 (23%), vagina in 4 (15%), anus in 3 (12%), ovary in 2 (8%), and other sites in 3 (12%) lesions. IHT was administered immediately before iridium 192 was placed and after its removal for 45-60 minutes at 41-44 degrees C. On December 31, 1991 median follow-up was 25 months (mean: 23 months; range: 5-65 months). At 3 months follow-up (FU), complete remission (CR) occurred in 17 (65%), partial remission (PR) in 7 (27%), and no change or progressive disease (NC/PD), in 2 (8%) lesions. At 12 months FU, in 16 of 21 patients (76%) local control (LC) was achieved, with 1 (5%) patient exhibiting a slow tumor regression. After combined IRT-IHT locoregional relapse or tumor regrowth occurred in 8/26 (31%): 5 (19%) outside and 3 (12%), inside the previously treated volume; relapses occurred within 8-30 (mean: 18) months of follow-up. Factors influencing initial (3 months FU) and long-term tumor response (12 months FU) included tumor class, tumor volume, total radiation dose, and thermal parameters with "good quality of heating" (TQ 41 degrees C > or = 75%) and high minimum tumor temperature (Tmin(av) > or = 41 degrees C). Treatment toxicity was acceptable: whereas 8 (31%) patients experienced acute side effects, which subsided within weeks, 7 (27%) developed long-term complications. Thermal damage was associated with IHT treatments exceeding maximum average temperatures of > or = 44 degrees C and maximum peak temperatures of > or = 45 degrees C.