Radiofrequency hyperthermia as adjuvant therapy following surgical resection of an experimental malignant neoplasm.

Local recurrence after radical surgery is a major problem with many primary solid cancers. The use of radiofrequency hyperthermia (RFHT) as adjuvant therapy to surgery was explored in the Fischer bladder carcinoma (FBCa)/F344 rat tumor system. After subcutaneous innoculation of 34 rats with 10(6) FBCa cells in suspension, RFHT was administered to 17 animals on days 1, 5, 8, and 12. The development of palpable tumors was delayed but not prevented, and tumor growth was retarded in RFHT-treated animals. In another experiment 40 rats were innoculated by subcutaneous trocar injection with a 1 mm3 piece of FBCa. After tumor excision on day 17, adjuvant therapy (untreated control, mitomycin C, RFHT, or RFHT plus mitomycin C) was started on day 20 (10 rats/treatment). The 20 RFHT-treated rats had only 1 incisional recurrence as compared to 9 recurrences in sham-heated rats (P less than 0.005). The authors conclude that RFHT has considerable value as adjuvant therapy to surgery in these tumors. Additional studies of RFHT as adjuvant treatment after surgical excision of tumors are planned.