Background Sentinel lymph node biopsy is a standard staging procedure for early axillary lymph node‐negative breast cancer. As an alternative to the currently used radioactive tracers for sentinel lymph node (SLN) detection during the surgical procedure, a number of studies have shown promising results using superparamagnetic iron oxide (SPIO) nanoparticles. Here, we developed a new handheld, cordless, and lightweight magnetic probe for SPIO detection. Methods Resovist (SPIO nanoparticles) were detected by the newly developed handheld probe, and the SLN detection rate was compared to that of the standard radioisotope (RI) method using radioactive colloids (99mTc) and a blue dye (indigo carmine). This was a multicenter prospective clinical trial that included 220 patients with breast cancer scheduled for sentinel node biopsy after a clinical diagnosis of negative axillary lymph node from three facilities in Japan. Results Of the 210 patients analyzed, SLN was detected in 94.8% (199/210 cases, 90% confidence interval [CI]) with our magnetic method and in 98.1% (206/210 cases, 90% CI) with the RI method. The magnetic method exceeded the threshold identification rate of 90%. Conclusion This was the first clinical study to use a novel handheld magnetometer to detect SLN, which we demonstrate to be not inferior to the RI method.

Heat shock protein (Hsp) 90 is a key regulator of a variety of oncogene products and cell-signaling molecules, and the therapeutic benefit of its inhibition in combination with radiation or chemotherapy has been investigated. In addition, hyperthermia has been used for many years to treat various malignant tumors. We previously described a system in which hyperthermia was induced using thermosensitive ferromagnetic particles (FMP) with a Curie temperature (Tc = 43°C) low enough to mediate automatic temperature control, and demonstrated its antitumor effect in a mouse melanoma model. In the present study, we examined the antitumor effects of combining a Hsp90 inhibitor (geldanamycin; GA) with FMP-mediated hyperthermia. In cultured B16 melanoma cells, GA exerted an antitumor effect by increasing the cells' susceptibility to hyperthermia and reducing expression of Akt. In an in vivo study, melanoma cells were subcutaneously injected into the backs of C57BL/6 mice. FMP were then injected into the resultant tumors, and the mice were divided into four groups: group I, no treatment (control); group II, one hyperthermia treatment; group III, GA alone; and group IV, GA with hyperthermia. When exposed to a magnetic field, the temperature of tissues containing FMP increased and stabilized at the Tc. In group IV, complete regression of tumors was observed in five of nine mice (56%), whereas no tumor regression was seen in groups I-III. Our findings suggest that inhibition of Hsp90 with hyperthermia increases its antitumor effect. Thus, the combination of FMP-mediated, selfregulating hyperthermia with Hsp90 inhibition has important implications for the treatment of cancer. (Cancer Sci 2009; 100: 558-564) H yperthermia is used in the treatment of tumors because tumor cells are more sensitive to temperature in the range of 42-45°C than are normal tissue cells.(1-4) Still higher temperatures (up to 56°C) lead to widespread necrosis, coagulation, or carbonization in a process called 'thermoablation'. Hyperthermia has an advantage over thermoablation in that it has fewer side effects, and its use, alone and in combination with chemotherapy or radiation, in the treatment of a wide variety of malignant tumors has been investigated in both experimental animals and in patients.(5) The most commonly used method of heating in clinical settings is capacitive heating using a radiofrequency electrical field.(4,6,7) The great advantage of capacitive heating is that it is non-invasive. However, this method can cause excessive heating of the fat layer and is not suitable for site-specific hyperthermia because it is difficult to selectively heat only the local tumor region to the intended temperature without also damaging normal tissue. This is because as the electrical field energy is conducted through the normal tissue, it is imperfectly transduced to heat in a manner reflecting the specific rates of absorption by the tissues, which are dependent on their specific electrical properties (e.g. permittivity and resistance).To overcome the disa...

Intraoperative sentinel lymph node mapping using ferumoxides and a highly sensitive magnetometer is a safe, accurate, and sensitive way to detect sentinel lymph nodes in non-small cell lung cancer patients.

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