Treating breast tumors with high-intensity focused ultrasound (HIFU) may leave tumor antigens behind, which could stimulate the immune system to fend off the disease, according to Chinese researchers. Should their results hold up over time, it could give HIFU a greater role in cancer treatment, beyond its immediate thermal effect on tumors.
For this research, Dr. Feng Wu, Ph.D., and colleagues enrolled 23 women, the majority of whom had stage II disease, invasive breast carcinoma, and a median tumor diameter of 3.1 cm. Wu's team is from Chongqing University of Medical Sciences in Chongqing, China.
The HIFU therapy system consisted of a transducer with a 12-cm diameter and a focal length of 90 mm (Model-JC, Chongqing Haifu Technology, Chongqing, China). The transducer operated at a frequency of 1.6 MHz. The median treatment time was 1.3 hours with the area of ablation extending 1.5-2 cm beyond the visible breast lesion.
All patients underwent modified radical mastectomy within two weeks of HIFU, and breast specimens were submitted to the pathology department. The researchers sought various biological markers, including proliferating cell nuclear antigens (PCNA), estrogen receptors, progesterone receptors, and heat-shock protein 70 (HSP-70).
According to the results, positive immunostaining for PCNA and estrogen and progesterone receptors were confined to the nuclei of the breast cancer cells. Nuclear positivity for PCNA was not detected in any of the treated samples; nuclear positivity for estrogen and progesterone receptors was found in 18% of the samples. The positive rate of epithelial membrane antigen (EMA) was 100%.
"The results show a variety of antigen expressions of HIFU-ablated tumor cells, with and without typical characteristics of thermal damage," the group wrote. "The most striking change seen in this study was the positive expression of EMA and HSP-70 on the treated cancer cells." While EMA is a glycoprotein that is found in normal breast cells, HSP-70 enhanced tumor cell immunogenicity, they added (Annals of Surgical Oncology, December 24, 2006).
Future research will have to look at whether these antigens can be used to directly induce anti-tumor immunity after HIFU treatment, they stated.
By Shalmali Pal
AuntMinnie.com staff writer
February 26, 2007
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