The effect of hyperthermia on cervical lymph node metastasis

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(1). IntroductionThis paper reports the effect of hyperthermia on cervical lymph node metastases of buccal mucosa squamous cell carcinoma O-1N in hamsters.(2). Materials and MethodsFifty golden hamsters in which O-1N was transplanted into the cheek pouch were divided into 3 groups : a heating group (21 animals) subjected to RF hyperthermia at 43ﾟC for 40 minutes twice a week, a sham group (15 animals) in which a sensor was inserted into the tumor for 40 minutes twice a week, and an untreated group (14 animals). When the tumor reached 7mm in diameter, it was heated with a 13.56MHz RF capacitive heating system. A pair of applicators each consisting of a 15-mm-diameter electrode plate was applied to the cutaneous and mucosal surfaces for heating. Intratumoral temperature was measured continuously by the C-C thermocouple thermometer. Cervical lymph nodes (LNs) and buccal tumors were removed two, three and four weeks after the experiment, respectively. LNs were histologically evaluated for the incidence of metastases and classified into a marginal-sinus metastatic type, a medullary-sinus metastatic type, an entire-node metastatic type and an extra-node metastatic type.(3). ResultsIn the heating group, incidence of metastases were reduced to 38% (8 of 21 animals) and metastases were seen within the LN capsule, whereas metastases were observed in 60% (9 of 15 animals) in the sham group and 71% (10 of 14 animals) in the untreated group and the extra-node metastatic type was found in both control groups. When the buccal tumor disappeared after heating, very few (8%) LNs metastases were found histologically, whereas matastases increased to 77.8% in the oral cancer regrowth group. Thus hyperthermia appeared to inhibit cervical LN metastasis as a result of the thermal effect on oral carcinoma.