The aim was to assess the response to the treatment using thermal radiofrequency ablation in patients with pelvic recurrent rectal cancer. The location of the lesions as well as the placement of the percutaneous probe were guided by computed tomography. All ablations were performed with a RITA Medical Systems Starburst XL (nine-array, 5-cm) thermal ablation catheter and the Model 1500 generator (RITA Medical Systems, Inc.). The radiofrequency ablation treatment was performed in two patients with pelvic recurrent rectal cancer with poor response to chemoradiotherapy with no indication of new surgical treatment and suffering strong pain in the sacrum area. The serum carcinoembryonic antigen had a sharp reduction in a sixty-day period. The post-procedure tomography analysis showed the center of the tumor with necrosis and a ring of edema around it. Both patients had no complaints about the procedure, and they needed to take mild analgesics only on the first day right after the procedure for pain. In the follow-up one patient developed an abscess and needed to be readmitted but without recurrent pelvic pain. An effective response was shown by tumor necrosis and total relief of pain of the sacrum area.