Radiation Therapy Advances in Lung Cancer Treatment

Findings from a recent study conducted by scientists at The University of Texas MD Anderson Cancer Center support the standard use of the more accurate intensity-modulated radiation therapy (IMRT) for patients with locally advanced, incurable non-small cell lung cancer (NSCLC) as opposed to the alternative 3D-conformal radiation therapy (3D-CRT). According to the research, which was published in JAMA Oncology today, IMRT had identical survival rates but fewer adverse effects.

In the Phase III NRG Oncology-RTOG 0617 randomized trial, 483 patients underwent prospective secondary analysis of long-term outcomes. The results showed that patients treated with 3D-CRT had a significantly higher risk of developing severe pneumonitis, or lung inflammation, compared to those treated with IMRT, with rates of 8.2% and 3.5%, respectively.

Lead author Stephen Chun, M.D., an associate professor of radiation oncology, believes that this study will put an end to the long-running discussion about the best radiation treatment for locally advanced NSCLC.

“3D-CRT is a rudimentary technique that’s been around for over 50 years. Our findings show it’s time to routinely adopt IMRT over 3D-CRT for lung cancer, just like we did for prostate, anal, and brain tumors decades ago,” Chun said. “The improved precision of IMRT translates into real benefits for patients with locally advanced lung cancer.”

Because 3D-CRT cannot bend or curve to form complicated forms, it exposes neighboring organs to needless radiation when it directs radiation in straight lines toward malignancies. Developed in the 1990s, IMRT dynamically modulates several radiation beams to tailor radiation to the shape of tumors using sophisticated computational techniques.

Radiation delivery from several directions can result in a low-dose radiation bath, or a vast area exposed to radiation below 5 Gray (Gy), even if it can also save normal tissue and deliver radiation more precisely.

Though there is strong evidence of IMRT’s other benefits, the unknown, long-term effects of this low-dose soaking on the lungs have spurred a historic dispute over IMRT and 3D-CRT in lung cancer. The results of this investigation demonstrated that there was no correlation between the low-dose radiation bath and an excess of secondary malignancies, long-term toxicity, or survival with long-term follow-up.

Patients receiving IMRT had five-year overall survival rates (30.8%) that were statistically equivalent to those receiving 3D-CRT (26.6%), and progression-free survival rates (16.5% vs. 14.6%) that were numerically better. When combined, these findings supported IMRT even though patients receiving the treatment had tumors that were noticeably bigger and more of them in sites that were adverse to the heart.

These results underscore the significance of utilizing IMRT to reduce cardiac exposure to doses ranging from 20 to 60 Gy. Although lung exposure has always been the main cause for concern, this study showed that, in a multivariable analysis, the quantity of the heart exposed to 40 Gy independently predicted survival. In particular, the median survival for patients who had less than 20% of their heart exposed to 40 Gy was much higher—2.4 years—than the median survival for patients who had more than 20% of their heart exposed to 40 Gy, which was 1.7 years.

“With a substantial number of patients reaching long-term survivorship for locally advanced lung cancer, cardiac exposure can no longer be an afterthought,” Chun said. “It is time for us to focus on maximizing radiation precision and conformity to reduce cardiopulmonary exposure and to let go of historic concerns over the low-dose bath.”

For more information: Long-Term Prospective Outcomes of Intensity Modulated Radiotherapy for Locally Advanced Lung Cancer, JAMA Oncology, doi:10.1001/jamaoncol.2024.1841