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Expert Point of View: Catherine C. Park, MD, FASTRO


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Catherine C. Park, MD, FASTRO

Catherine C. Park, MD, FASTRO

Discussant of the 12-year report from the NRG/RTOG 9804 trial, Catherine C. Park, MD, FASTRO, Professor and Chair of the Department of Radiation Oncology at the University of California, San Francisco, underscored the high prevalence of ductal carcinoma in situ, which comprises approximately 20% to 25% of all new breast cancer diagnoses in the United States and abroad. She emphasized that these results should inform meaningful patient-physician discussion.

“This is an important trial for us to be considering,” said Dr. Park, who noted that treatment options for patients with ductal carcinoma in situ are the same as those offered to patients who have invasive cancer. They include radiation therapy to the breast and for those with estrogen receptor–positive disease, hormonal therapy.

“The earliest trials in ductal carcinoma in situ showed us that patients benefited from radiation therapy by a reduction of about 50% of proportional reduction in risk, and the addition of tamoxifen further reduced that risk by about 50% on average,” Dr. Park continued. “However, we still realized that if you look at the whole population of patients with ductal carcinoma in situ, we were likely overtreating many patients for whom survival will likely not be impacted by local therapies or perhaps even hormonal therapies in the long run.”

Additional Radiation Therapy: A Personal Decision

According to Dr. Park, efforts made by Dr. McCormick and colleagues have been instrumental in identifying patients with favorable biology upfront. She asks the question of how much intervention is really necessary?

“There is a local regional reduction with radiation in these very favorable patients,” said Dr. Park. “However, for many of these patients, because their absolute benefits will be relatively small, a personal discussion with their physician concerning their preferences is needed to understand their tolerance for risk versus moving forward with the benefits of therapy.”

Dr. McCormick responded by reiterating the importance of meaningful patient-physician discussions about the risks and benefits of additional therapy. “When we sat down with statisticians a number of years ago to put this trial together, we assumed that because this was low-risk ductal carcinoma in situ, the impact of radiation would actually be lower than the 50% mentioned,” said Dr. McCormick. “Even though the starting point of about 1% per year is very low, the reduction is more than 70% with this group. I think that was one of the bigger surprises. However, many patients have different definitions of risk tolerance, so it’s important for this information to be used when they meet with their doctors.” 

DISCLOSURE: Dr. Park reported no conflicts of interest.


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