Innovative new technique of partial breast irradiation for early stage breast cancer

August 08, 2015

The pilot study has used this treatment technique in 36 patients to date, as the sole method of radiation treatment for early stage breast cancer. It involves implanting permanent radioactive seeds directly into the area of the tumour under local anaesthetic in a single one hour session instead of daily treatments over several weeks.

"This technique allows for radiation to be focused directly to the small area where the tumour was removed, without the need to irradiate the entire breast", states Dr. Jean Philippe Pignol, of the Toronto Sunnybrook Regional Cancer Centre and CARO researcher. Clinical assessments after the implant on these 36 women, demonstrated a much better tolerance compared to standard radiation treatment. One patient presented with a mild skin discolouration and two patients experienced minor bruising for a few days after the implant.

"Intermediate analysis suggests that this method of treatment for early stage breast cancer is well tolerated and also more convenient for patients. The expected benefit is a reduced treatment burden regarding time commitment and less acute skin reactions. Long term tolerance and local control outcomes are currently being collected in an ongoing Phase 1/11 clinical trial with an accrual target of 65 patients", states Dr. Eileen Rakovitch, breast cancer radiation oncologist specialist in Toronto.

Both Dr. Pignol and Dr. Rakovitch are members of the Canadian Association of Radiation Oncologists, a national organization which is the official voice of radiation oncology.

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"Here we had an effect on the level of the N-CoR protein without affecting the level of N-CoR mRNA," Katzenellenbogen said. "This is the result of the initial effect of estrogen on gene expression, which was to up regulate the mRNA levels for a ubiquitin ligase. So by changing the level of this ligase, it had a dramatic effect on the level of N-CoR protein without affecting gene expression for N-CoR itself."

This "secondary effect" may have broad implications for other important cellular activities, the researchers theorize. Reductions in N-CoR over time also could promote cancer development in other sites, such as the uterus, and could adversely affect the desired activities of vitamin D, retinoid and thyroid receptors, Katzenellenbogen said.

The study sheds light on the impact of estrogen on certain cells, as well as how tamoxifen works as an anti-estrogen to facilitate recovery of N-CoR, she and Frasor said.

"Eventually," Katzenellenbogen said, "understanding more of the mechanisms involved could lead to the development of other related agents that might reduce some of the unwanted side effects of tamoxifen, such as stimulation of the uterus."

In addition to Katzenellenbogen and Frasor, Jeanne M. Danes, a researcher in the department of molecular and integrative physiology, and doctoral student Cory C. Funk were co-authors of the study.

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