SAN FRANCISCO-Stereotactic body radiation therapy (SBRT) safely reduced the spread of early stage lung cancer and prolonged survival in elderly patients with inoperable disease, according to the results of a retrospective analysis presented at the 2017 Multidisciplinary Thoracic Cancers Symposium (Abstract 111).
"Patients in their 80s and 90s who have early stage lung cancer but cannot undergo an operation can be treated safely and effectively with SBRT," said lead investigator Richard J. Cassidy, MD, a resident in radiation oncology at the Winship Cancer Institute of Emory University, Atlanta.
Multiple studies and trials have established the effectiveness of SBRT for inoperable early-stage lung cancer; safety concerns have limited the use of SBRT in the elderly, concern about tolerating the treatment, and potential side effects, Cassidy commented in a press briefing.
However, the low rates of side effects reported in the study indicate such concerns should not keep oncologists from considering its use in inoperable elderly patients, he said.
SBRT is an advanced form of localized radiation therapy that uses complex image-guidance techniques to treat tumors with high accuracy. Further, treatment can be completed in 3-5 sessions over 1-1.5 weeks instead of 6-7 weeks of daily sessions needed with conventional radiation. In younger patients, SBRT is an accepted standard of care for medically inoperable early stage lung cancer, with treatment outcomes comparable to surgery.
Like intensity-modulated proton therapy, SBRT allows delivery of very precise, high-dose radiation to the tumor area. It uses complex radiation planning techniques including 4-D CT scan-based planning, breathing motion management, image-guided radiation therapy, and respiratory-gated radiation therapy. This allows delivery of radiation to small volumes of the lung, limiting damage to healthy tissue.
SBRT Study Results
The analysis involved 58 consecutive patients, age 80 or older, who received SBRT at four Emory sites between 2010 and 2015. Forty percent of the tumors were adenocarcinomas, 29 percent were squamous cell carcinomas, and no biopsy for 31 percent, although 50 percent had a history of lung cancer.
Cancer-specific survival (CSS) rates 2 years after SBRT were 73 percent, and 57 percent for overall survival (OS). Rates were higher for former smokers but lower for individuals with a prior lung cancer diagnosis as well as oldest subjects, Cassidy reported.
OS rates were higher for patients with higher Karnofsky Performance Status (KPS) (HR = 0.91) and higher scores were associated with lower rates of both local failure (HR = 0.92) and regional failure (HR = 0.94).
Cassidy noted this metric should be considered when offering SBRT to elderly patients, as certain performance status criterion were associated with significantly better outcomes.
At 2 years, overall local control and regional control were estimated to be 84.5 percent and 71.7 percent, respectively. Patients with adenocarcinomas were more likely to experience local failure (HR = 6.36), but failure was less common for patients with T1 tumors (HR = 0.20).
Just over one-third of patients (34.5%) experienced radiation pneumonitis, but only two patients experiencing grade 3+ pneumonitis. Pneumonitis was more common among patients not actively using ace-inhibitors, and less frequent in those with smaller tumors.
Clinical Significance
The projected increase in the elderly population in the coming years make research like this especially important, said panel moderator Pranshu Mohindra, MD, Assistant Professor of Radiation Oncology at the University of Maryland School of Medicine in Baltimore.
"The percent of the population 85 and older is projected to increase from 1.5 percent in the year 2000 to 2.3 percent in 2030, and 4.3 percent in 2050. Similar trends of rising number of octo- and nonagenarian are also seen in the lung cancer population, many of whom are in early stages," he told Oncology Times.
Coexisting medical comorbidities make treating such patients difficult, and highly effective treatment approaches with low toxicity are needed, he said, noting that no serious toxicities or deaths were reported in the study.
"While other institutions have reported similar experiences, this study provides 2-year outcomes displaying durability of the treatment effect. With increasing such published reports of safety and wide availability of SBRT capabilities, practitioners should strongly consider SBRT as a treatment option for elderly patients unfit for surgery instead of pursuing non-interventional strategies," Mohindra said.
Patients should understand that lung cancer detected at early stages is curable with effective treatments, he continued. While the standard of care treatment is surgery, this may not always be feasible due to suboptimal medical health.
"In the study, Dr. Cassidy indicates that even patients who are 80 years or older can receive curative treatment safely and effectively with SBRT, suggesting that concerns about toxicity should not prevent elderly patients from considering curative treatment," Mohindra noted.
He said patients should discuss this option with their pulmonologist and oncologists even when they feel that their medical health is not optimal. There is, however, some risk of toxicity and, therefore, a detailed discussion is needed with their radiation oncologist.
"Because of the safety and efficacy results reported in the study, practitioners should strongly consider SBRT as a treatment option for elderly patients unfit for surgery instead of pursuing non-interventional strategies or observation alone," said Mohindra. "Because untreated early stage lung cancer can rapidly progress over many months and can ultimately result in death, early treatment is critical."
The next step will be exploring the risks of using SBRT, especially for early stage lung cancers close to the central chest structures like larger airways, heart, great vessels, esophagus and spinal cord, Mohindra noted.
A recent clinical trial from the Radiation Therapy Oncology Group performed a safety analysis of a dose-escalation study to identify the safe dose for delivery of SBRT to central tumors, and follow-up data is pending. In addition, research efforts on developing ways to mitigate radiation pneumonitis are ongoing to further limit the risks in high-risk patients.
Kurt Samson is a contributing writer.