For the single-institution study, the researchers retrospectively analyzed 27 patients who received IMPT for a lung cancer recurrence between 2011 and 2016. All patients had received a prior thoracic radiation course with curative intent. Of the cohort, 22 (81 percent) were treated for non-small cell lung cancer. The median time to reirradiation after initial treatment was 29.5 months. At a median follow-up for all patients of 11.2 months – and 25.9 months for those still alive – the median overall survival (OS) was 18 months, with one year OS at 54 percent. Four patients (15 percent) experienced a local failure (LF), recurrence within the reirradiation field; 78 percent of patients did not experience a LF within the first two years of follow-up. At one year, 61 percent of patients were free from recurrence in the chest and lung, and progression-free survival was 51 percent. Of particular interest to the researchers, patients who received a higher dose of radiation had fewer local recurrences and improved progression-free survival. Reirradiation was well-tolerated, with two patients experiencing grade three pulmonary toxicity and none with severe esophageal toxicity. No patients experienced grade four or five toxicities. Historically, reirradiation of the lung was associated with moderate to severe toxicity, even fatal, toxicities in 20 to 30 percent of patients. “With the advancement of IMPT, we knew that we were able to generate more precise radiation treatment plans that spared normal tissue, but we weren’t sure if this would translate into beneficial clinical outcomes until we analyzed this data,” said Chang. “While the findings are early, we’re hopeful that we can offer more positive outcomes and low toxicity with IMPT for recurrent thoracic cancer patients who previously had few treatment options.”
Limitations of the study include its small size and retrospective data. Reirradiation with IMPT in other disease sites is an area of continued research interest; studies in head and neck cancer are ongoing at MD Anderson.
In addition to Ho and Chang, other authors on the all-MD Anderson study include: Quynh-Nhu Nguyen, M.D., Pamela K. Allen, Ph.D., Daniel R. Gomez, M.D., Ritsuko U. Komaki, M.D., Z. Liao, Stephen M. Hahn, M.D., Steven H. Lin, M.D., Ph.D., all of Radiation Oncology; Heng Li, Ph.D., Xiaodong Zhang, Ph.D., X. Ronald Zhu, Ph.D., and Michael T. Gillin, Ph.D., all of Radiation Physics.