The safety of weekly regional hyperthermia performed with 8 MHz radiofrequency (RF) capacitive heating equipment has been established in rectal cancer. We aimed to standardize hyperthermia treatment for scientific evaluation and for assessing local tumor response to RF hyperthermia in rectal cancer. Forty-nine patients diagnosed with rectal adenocarcinoma were included in the study. All patients received chemoradiation with intensity-modulated radiation therapy 5 days/week (dose, 50 Gy/25 times) concomitant with 5 days/week for five times of capecitabine (1700 mg/m2 per day) and once a week for five times of 50 min irradiations by an 8 MHz RF capacitive heating device. Thirty-three patients underwent surgery 8 weeks after treatment. Three patients did not undergo surgery because of progressive disease (PD) and 13 refused. Eight (16.3%) patients had a pathological complete response (ypCR) after surgery. Among patients without surgery, 3 (6.1%) had clinical complete response (CR) and 3 (6.1%) had local CR but distant PD (CRPD). Ninety percent of ypCR + CR patients were shown in 6.21 W min−1 m−2/treatment or higher group of average total accumulated irradiation output with 429°C min−1 m−2 or higher group of total accumulated thermal output. However, a patient with CRPD was in the higher total accumulated thermal output group. We propose a new quantitative parameter for the hyperthermia and demonstrated that patients can benefit from mild irradiation with mild temperature. Using these parameters, the exact output, optimal thermal treatment, and contraindications or indications of this modality could be determined in a multi-institutional, future study.

Background: Hyperthermia has not been approved as a standard treatment method in oncology. One of the major problems is that there is no reference point for this therapy. Another problem is that radiofrequency hyperthermia has a fatal flaw, the hot spot phenomenon, which does not allow continuation of treatment without lowering the output. Patients and Methods: Hyperthermia treatment was administered either alone or concomitantly with chemotherapy and/ or radiotherapy to 76 consecutive patients with malignancies, using Thermotron RF-8, between December 2011 and April 2014. Radiofrequency hyperthermia was administered 5 times for 5 weeks with 50 min irradiation in all patients. Results: Complete response (CR) was seen in 35.2% of primary cases, but in 4.5% of recurrent cases, and this rate was higher in patients with three days after first chemoradiation. There was significant correlation among the initial irradiation output at which complications occurred, initial time at which complications occurred and the physical status of the patients, such as visceral fat area. All patients with CR had significantly higher increased body temperature than the other patients. However, patients with progressive disease and 17 or more Hidaka output points showed significantly higher increased body temperature than patients with partial response or stable disease. Conclusions: Patients with CR had higher temperatures, but some patients with higher temperature also showed progressive disease. Further studies to examine the discrepancy between the clinical and histological response by using a large sample of surgically resected cases and to validate and reconfirm our findings are warranted.

We present a good predictive equation for initial energy output at which output-limiting symptoms occur. It is critical to prevent RF hyperthermia-induced output-limiting symptoms and establish new prevention strategies.

We previously reported that patients with a clinical complete response (CR) following radiofrequency thermal treatment exhibit significantly increased body temperature compared with other groups, whereas patients with a clinical partial response or stable disease depended on the absence or presence of output limiting symptoms. The aim of this study was to evaluate the correlation among treatment response, Hidaka radiofrequency (RF) output classification (HROC: termed by us) and changes in body temperature. From December 2011 to January 2014, 51 consecutive rectal cancer cases were included in this study. All patients underwent 5 RF thermal treatments with concurrent chemoradiation. Patients were classified into three groups based on HROC: with ≤9, 10–16, and ≥17 points, calculated as the sum total points of five treatments. Thirty-three patients received surgery 8 weeks after treatment, and among them, 32 resected specimens were evaluated for histological response. Eighteen patients did not undergo surgery, five because of progressive disease (PD) and 13 refused because of permanent colostomy. We demonstrated that good local control (ypCR + CR + CRPD) was observed in 32.7% of cases in this study. Pathological complete response (ypCR) was observed in 15.7% of the total 51 patients and in 24.2% of the 33 patients who underwent surgery. All ypCR cases had ≥10 points in the HROC, but there were no patients with ypCR among those with ≤9 points in the HROC. Standardization of RF thermal treatment was performed safely, and two types of patients were identified: those without or with increased temperatures, who consequently showed no or some benefit, respectively, for similar RF output thermal treatment. We propose that the HROC is beneficial for evaluating the efficacy of RF thermal treatment with chemoradiation for rectal cancer, and the thermoregulation control mechanism in individual patients may be pivotal in predicting the response to RF thermal treatment.

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