Advanced Proton Therapy Shows Future in Lung Cancer Recurrence Treatment

Intensity modulated proton therapy (IMPT) offers a promising treatment option for patients with lung cancer recurrence.

The American Cancer Society estimates that more than 225,500 individuals will be diagnosed with lung cancer in 2017, of whom 155,870 will die from the disease. The primary cause of death is recurrence.

Unfortunately, many recurrent lung cancer patients are not candidates for surgery, and response rates to second-line chemotherapy are poor; however, there has been increasing interest in the repeat use of radiation.

“Historically, repeat radiation at a higher, curative dose was not possible with older, less precise radiation techniques because the cumulative radiation dose necessary to treat the cancer would cause too much toxicity,” said lead author Jennifer Ho, MD. “In lung cancer, tumors are close to the esophagus, aorta, and spinal cord, and all of these critical structures are vital for the body to function. The protein beam—–and pencil beam in particular––provides much more conformal radiation, which means higher disease to tumors and lower dosages to critical structures nearby.”

IMPT is based on scanning beam technology that can simultaneously optimize the intensities and energies of all pencil beams to deliver a more precise dose of protons to tumors. It is one of the most advanced forms of proton therapy, according to the authors.

“The technology has the ability to destroy cancer cells while sparing healthy tissue from damage,” said corresponding author Joe Y Chang, MD, PhD. “Therefore, important quality of life outcomes can be preserved and severe toxicities have shown to be reduced.”

For the study, investigators retrospectively analyzed 27 patients who received IMPT for lung cancer recurrence between 2011 and 2016. All participants had received a prior thoracic radiation course with curative intent. Of the 27 patients, 22 were treated for non-small cell lung cancer. The median time to reirradiation after initial treatment was 29.5 months.

At median follow-up of 11.2 months for all patients and 25.9 months for those still alive, the median overall survival (OS) was 18 months, with 1 year OS at 54%.

Four patients experienced a local failure—recurrence within the reirradiation field— whereas 78% of patients did not experience a local failure within the first 2 years of follow-up. Sixty-one percent of patients were free from recurrence in the chest and lungs at 1 year, and progression-free survival was 51%.

Interestingly, patients who received a higher dose of radiation had fewer local recurrences and saw improvement in progression-free survival.

Reirradiation was well-tolerated, with only 2 patients who experienced grade 3 pulmonary toxicity and none with severe esophageal toxicity. There were no reports of grade 4 or 5 toxicities. Historically, reirradiation of the lung was associated with moderate-to-severe toxicity, even fatal toxicities, in 20% to 30% of patients, according to the study.

Study limitations were the small size and retrospective data used.

“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 the data,” Chang said. “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.”

Findings from the single-institution study were presented at the 2017 Multidisciplinary Thoracic Cancers Symposium.