Findings a Less Toxic Radiation Therapy for Lung Cancer

Intensity modulated radiation therapy shows less intense lung toxicity for more tolerable chemotherapy.

Recent findings from a clinical trial offered hope for more tolerable chemotherapy treatment regimens among patients with lung cancer.

The international, cooperative-led trial of patients with locally advanced non-small cell lung cancer (NSCLC) suggests that intensity modulated radiation therapy (IMRT) has less intense lung toxicity for more tolerable chemotherapy, compared with patients receiving 3-dimensional conformal radiation therapy (3-D CRT).

Lung cancer is one of the deadliest forms of cancer, with 221,000 people diagnosed in 2015 and 158,000 deaths from the disease, according to the American Cancer Society.

Approximately 33% of all lung cancers are diagnosed when the cancer is locally advanced, according to Stephen Chun, MD, Radiation Oncology fellow at The University of Texas MD Anderson Cancer Center.

The current standard of care for this type of lung cancer is concurrent chemotherapy and radiation, with many patients receiving either 3-D CRT or IMRT.

Treatment with 3-D CRT has been the standard of care for lung cancer over the past few decades. The technique shapes radiation beams aimed in straight lines to match the shape of the tumor.

Contrarily, IMRT is a newer, more “high-tech” method that sculpts and molds radiation beams to tumor targets, using significantly more complicated radiation beam arrangements than 3D-CRT.

In turn, IMRT can save more normal tissue than 3D-CRT with high doses of radiation, according to Dr. Chun.

“IMRT was developed more than a decade ago and because it’s been shown to reduce toxicity, it has been accepted to treat prostate, brain, and head and neck cancers,” Dr. Chun said. “There have been a number of smaller studies, including research led by MD Anderson, looking at IMRT and lung cancer. This the first analysis of a prospective clinical trial to show a reduction of toxicity associated with IMRT in locally advanced lung cancer and could lead to a major change in the way radiation therapy is delivered for the disease. The data from our study makes a strong argument that we should routinely consider use of IMRT in locally advanced lung cancer.”

The study comes after a collection of data from NRG/RTOG 0617, a large, multi-center phase 3 randomized trial of patients with locally advanced NSCLC.

That study recruited patients from 2007 to 2011, comparing high doses of 74 Gy to the standard dose of 60 Gy. All patients then had chemotherapy and either 3-D CRT (47%) or IMRT (53%).

The findings showed 44% fewer cases of severe pneumonitis in patients who received IMRT. Pneumonitis is characterized by researchers as lung inflammation that requires oxygen, steroids or mechanical ventilation, and/or death.

Just 3.5% of patients treated with IMRT were affected, compared with 7.9% of the 3-D CRT group. While the benefit of IMRT was seen in all tumor sizes, the reduction of severe pneumonitis was more pronounced in larger tumors, Dr. Chun noted.

Additionally, patients who received treatment with IMRT were more likely to complete consolidative chemotherapy. The standard of care for locally advanced lung cancer is high dose chemotherapy following chemotherapy with radiation.

One of the mainstays of IMRT is to bring in many complex beams to converge on a single target, maximizing the dose on the target and dramatically saving adjacent tissue. Using multiple beam arrangements has allowed for the spreading of a low-dose bath, such as the volume of lung that received 5 Gy of radiation.

As IMRT is more expensive in both time and money, scientists thought they would see a dramatic increase in severe toxicities, but instead witnessed a steady reduction. These findings could reduce the number of hospital admissions and improve the quality of life for patients in this population.

“It’s been unclear what the consequences of that low dose bath are,” Dr. Chun said. “What we’ve seen in this study is that indicators of the low dose bath that’s increased by IMRT had no association with any severe toxicity outcome. This finding suggests that we should be optimizing radiation treatment by the high and intermediate dose region, and not the low dose region.”