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Experts debate partial breast irradiation vs. omission of radiation therapy for low-risk breast cancer
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MIAMI — Two speakers at Miami Breast Cancer Conference debated whether partial breast irradiation or omission of radiation therapy is a preferable strategy for certain patients with low-risk breast cancer.
Although data support de-escalation in the form of shorter courses of radiation for low-risk breast cancer, omitting radiation therapy is the only way to eliminate the potential burden, toxicity and cost of this treatment for carefully selected patients.
“This is about choosing the right treatment for the right patient. There are areas of controversy where we still need more evidence,” Reshma Jagsi, MD, DPhil, professor and deputy chair of radiation oncology at University of Michigan, said during her presentation.
Omitting radiation
Radiation therapy is associated with some degree of toxicity, treatment burden and expense.
Hypofractionation — which includes accelerated or partial breast irradiation — does not fully eliminate the costs, Jagsi said.
“There are concerns about using partial breast irradiation, so we have to be mindful about using it. Ideally, we would be selecting for treatment patients who are likely to benefit and spare those who are at low risk after surgery and systemic therapy alone,” Jagsi said.
Multiple trials have shown radiation therapy nearly halves the rate of disease recurrence, but not all patients have the same locoregional recurrence risk after lumpectomy alone.
“The Holy Grail has always been to find the low-risk population of patients [for whom] the risk for recurrence is low in the absence of radiation, so that we can actually omit radiation altogether,” Jagsi said.
The risk for ipsilateral breast cancer recurrence has decreased due to improvements in screening, surgical practices and systemic therapy, Jagsi said. However, studies designed to evaluate the omission of radiation that have included patients selected based upon clinical and pathologic characteristics alone have largely proven unsuccessful.
“My recommendation is that select patients with invasive breast cancer may reasonably omit radiation in the process of shared decision-making,” Jagsi said. “For women with invasive breast cancer, those who may omit radiation therapy are women aged 70 years and older — maybe 65 years and older based upon long-term follow-up of PRIME II data — with ER-positive stage I tumors. But, they must be informed and willing to accept the 10-year risk of 10% recurrence.”
Ongoing trials are seeking to identify even more candidates for whom omission of radiation therapy may be an option, she said.
Partial breast irradiation
Frank A. Vicini, MD, FACR, FABS, FASTRO, radiation oncologist at 21st Century Oncology, argued that partial breast irradiation should be considered for low-risk patients. This includes patients aged younger than 65 to 70 years with tumors less than 2 cm and ER/PR-positive, HER2-negative, grade 1 to grade 2, node-negative disease.
“Omission of radiation therapy generally means 5 years or more of hormonal therapy. Most patients would prefer less than 5 days of partial breast irradiation vs. 5 years of hormonal therapy,” Vicini said during his presentation. “Also, partial breast irradiation alone is an attractive option as it spares patients morbidity.”
The toxicity of hormonal therapy — specifically aromatase inhibitors — is underappreciated, Vicini said.
Apart from joint and muscle aches and osteoporosis risks, accumulating evidence suggests hormonal therapy is associated with significant cardiovascular risk.
Outcomes among patients who undergo partial breast irradiation and whole breast irradiation are equal, Vicini added.
“We now have more than 11,000 women [randomly assigned] in phase 3 trials to the two types of irradiation,” he said. “The differences in local failure are very minimal and, in most studies, not statistically significant.”
– by Jennifer Southall
Reference:
Jagsi R and Vicini FA. Medical Crossfire: Optimal de-escalation in patients undergoing BCT for pN0 breast cancer: Partial breast irradiation or omission? Presented at: Miami Breast Cancer Conference; March 7-10, 2019; Miami.
Disclosures: Jagsi and Vicini report no relevant financial disclosures.