Targeted Radiation Therapy Can Control Limited Cancer Spread

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Title: Targeted Radiation Therapy Can Control Limited Cancer Spread
URL: http://www.pslgroup.com/dg/2286BA.htm
Doctor's Guide
August 13, 2008

CHICAGO -- August 13, 2008 -- Precisely targeted radiation therapy can eradicate all evidence of disease in selected patients with cancer that has spread to only a few sites suggests the first published report from an ongoing clinical trial.

In the August 15 issue of Clinical Cancer Research, researchers from the University of Chicago Medical Center, Chicago, Illinois, report that targeted radiation therapy had completely controlled all signs of cancer in 21% of patients who had 5 or fewer sites of metastatic disease.

"This was proof of principle in patients who had failed the standard therapies and had few, if any, remaining options," said the study's senior author, Ralph Weichselbaum, MD, University of Chicago Medical Center. "We had encouraging results, including several long-term survivors, in patients with stage IV cancers that had spread to distant sites."

Patients with stage IV cancer with 1 to 5 distant metastases and no tumours >10 cm in diameter were eligible to participate in the study either before or after chemotherapy treatment. Each patient received 3 doses, separated by at least 2 days, of precisely targeted radiation therapy focused on each metastatic tumour. The first patients in the study received lower doses. As few side effects were seen, radiation doses were gradually increased in subsequent groups of patients.

From November 2004 through February 2008, 29 patients, with a total of 56 cancerous lesions, enrolled in the trial. Of the 29 patients, 24 had progressed after at least 1 round of systemic chemotherapy. For the other 5, there was no promising choice of therapy. Six of the 29 initial patients had lasting tumour control, with no detectable evidence of disease 15 months after treatment. Many patients had a complete response in at least 1 tumour. Thirty-one of the 56 treated tumours completely disappeared. Two tumours had a partial response, defined as reduction in tumour volume of more than 30%. Only 3 of the 56 tumours progressed, growing in size by 20% or more during the treatment phase.

Tumour control improved as the radiation dose increased. Thirty-nine percent of the 31 tumours treated with 24 Gy of radiation met the criteria for tumour control -- a complete or partial response. That increased to 79% for the 19 tumours treated with 30 Gy and to 83% for the 6 tumours treated with 36 Gy.

"This suggests that the initial doses were too low," said lead author of the study Joseph Salama, MD, University of Chicago Medical Center. "We have seen improved response rates with higher radiation doses without an increase in side effects yet."

Patients tolerated the treatment, the authors wrote, with "limited difficulty." All had some fatigue, but few had serious side effects.

Crucial to this approach is careful patient selection, distinguishing between patients who have a treatable number of tumours and those who have widespread metastasis, including multiple tumours too small to detect.

The technique could also be applied after chemotherapy, the authors suggested, in cases where the drugs had eliminated most of the smaller cancer, leaving only a few larger tumours behind.

SOURCE: University of Chicago Medical Center

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