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Can Lower Radiation Doses Reduce Damage to Immune System and Improve Outcomes in NSCLC?

By: Joseph Fanelli
Posted: Thursday, August 1, 2019

New findings presented in the International Journal of Radiation Oncology • Biology • Physics suggest that higher doses of radiation in patients diagnosed with stage III non–small cell lung cancer (NSCLC) may be associated with tumor progression and death after definitive treatment. Sameer K. Nath, MD, of the University of Colorado Cancer Center, Aurora, and colleagues believe their findings indicate that tailoring radiation therapy to strengthen the immune system could be an important factor in improving outcomes in this patient population in the future.

“We show that the estimated dose of radiation to immune cells is an important predictor of tumor control and survival,” Dr. Nath said in a University of Colorado press release. “In fact, it ends up being one of the most important predictors.”

The investigators retrospectively identified 117 patients diagnosed with stage III NSCLC who were treated with definitive fractionated radiation therapy. The authors then calculated the estimated dose of radiation to immune cells as a function of the number of radiation fractions and mean doses delivered to the lungs, heart, and rest of the body.

After a median follow-up of 16 months, the patients had a 5-year overall survival rate of 11.2%, with a median survival of 17.3 months. The mean estimated dose of radiation to immune cells for the patient population was 6.1 Gy, and patients with higher estimated doses experienced a greater risk of grade 3 or less lymphopenia.

The estimated dose of radiation to immune cells was associated with overall survival (hazard ratio = 1.17), local progression-free survival (hazard ratio = 1.17), and disease-free survival (hazard ratio = 1.15). For those patients with an estimated dose of radiation to immune cells ratio higher than 7.3 Gy and lower than 5.1 Gy, overall survival rates were 14.3 months and 28.2 months, respectively.

“Now that we have ways to estimate this radiation dose, we can look at sparing the immune system as an organ-at-risk,” Dr. Nath said. “We can focus on methods to minimize dose and in doing so, we will be able to maximize the benefit of radiation to these patients.”

Disclosure: The study authors reported no conflicts of interest.

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