Decade of SBRT Use Seals Its Role in Early Lung Cancer

Pam Harrison

November 03, 2014

Long-term experience using high-dose stereotactic body radiotherapy (SBRT) confirms that this highly focused, rigidly delivered, and tightly controlled radiation approach results in excellent local control and minimal toxicity in most patients with medically inoperable, early-stage lung cancer, report researchers from the Cleveland Clinic Foundation.

"When we developed our program in 2003, we decided early on to stick with one form of delivery and be very conservative in order to understand how SBRT worked, not only from a cancer point of view but also from a safety point of view, because these patients are relatively fragile," Gregory Videtic, MD, a radiation oncologist at the Cleveland Clinic Foundation, stated at a news briefing during the 2014 Chicago Multidisciplinary Symposium in Thoracic Oncology.

"And over our 10-year experience with SBRT, only 13% of patients had any form of toxicity related to the SBRT," Dr Videtic commented. He added that it was also striking that SBRT is very good at eradicating the tumor at the treatment site, even though it is the comorbidities that patients present with initially that drives their overall survival rate.

Dr Videtic is also associate professor of radiation oncology at the Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, Ohio. In this study, he and his colleagues surveyed their prospective SBRT registry for all patients with medically inoperable non–small cell lung cancer (NSCLC) who were treated with 50 Gy in five fractions ― the so-called "50 -in-5" regimen ― between October 2003 and December 2012.

The system used from the outset by the Cleveland Clinic is the Novalis/BrainLAB platform. Patients are prepared for the delivery of SBRT in this platform through the use of BodyFIX (Elekta AB) ― essentially, a vacuum bean bag that is moulded to the patient to provide rigid immobilization.

"We also consistently use abdominal compression to make sure there is very little motion when we deliver the SBRT," Dr Videtic explained.

A system called ExacTrac (Brainlab AG) helps clinicians verify that they are accurately targeting and delivering the radiation to the malignant lesion only and not to normal structures.

During the 10 years of experience using SBRT for this patient population, 300 patients and a total of 340 lesions were treated at the Cleveland Clinic. The median age of the patients was 74 years; more than half were women, and the median forced expiratory volume (FEV1) was 59% of predicted.

The median tumor diameter was 2.4 cm, and for some 36% of the tumors treated with SBRT, biopsy results were unavailable or the biopsy specimens were nondiagnostic.

The primary reason for being ineligible for surgery was pulmonary (in about two thirds of patients), and slightly more than 18% of patients were tobacco smokers at the time they received SBRT.

Most patients required only one course of SBRT, which is initiated on a Monday and is finished on the following Friday.

However, 15% of patients required two or more courses of SBRT, owing to the recurrence of a second early cancer.

No High-Grade Toxicity

"There were no grade 4 or 5 toxicities," Dr Videtic reported, "and in general, 75% to 80% of the toxicities that these patients experienced were minor and resolved within short periods of time."

Several years into the Cleveland Clinic SBRT program, clinicians began to divide patients into two groups, those with central lesions in the middle of the chest (roughly 34% overall), and those with noncentral lesions closer to the ribs.

Patients with tumors closer to the ribs did experience more chest wall toxicity (15.5%) than those with tumors in the middle of the chest (11.7%).

However, as Dr Videtic emphasized, "it didn't seem to matter where the tumor was ― in the middle of the chest or in the periphery of the chest ― SBRT is still very safe, and it doesn't drive any extra toxicity."

The median follow-up period for the group overall was approximately 18 months.

At the time of the current analysis, almost 47% of the patients were still alive.

Table. Five-Year Actuarial Disease Control and Survival Rates

  Local Control Distant Metastases - Free Disease Failure - Free Overall Survival
Central lesions 79% 49.5 37.2 18.3
Noncentral lesions 74.5% 56.7 34.3 20.3

"Even though we might have eradicated the cancer in the lung, as time went on, the cancer appeared distantly," Dr Videtic noted. At about 5 years, roughly half of the patients did develop some form of metastatic disease, "although this is not out of keeping with some of the surgical series we might see," Dr Videtic noted.

On the other hand, overall survival rates at 5 years were modest because the initial comorbidities that restricted the use of surgery in these patients drove much of the survival risk.

"This is an amazing technology for a population of patients who previously had no other options," Dr Videtic concluded. "Given that lung cancer is so preponderant, between 15,000 to 20,000 people a year could be considered for SBRT because they can't handle surgery."

Standard of Care

Asked to comment on the study, Stephen Hahn, MD, professor and chair, Department of Radiation Oncology, University of Pennsylvania's Perelman School of Medicine in Philadelphia, told Medscape Medical News that SBRT is more labor intensive than standard radiation therapy. It requires considerably more physician and technical input than standard radiation approaches, and imaging is critical to the success of the technique, he said.

This may restrict its use in smaller centers where they may not have the capacity to offer SBRT, he suggested.

On the other hand, virtually all academic centers are now able to offer SBRT to appropriate candidates.

In fact, SBRT rapidly became standard of care after its introduction because short-term outcomes suggested the approach is highly efficacious, as Dr Hahn suggested.

"What we didn't have until now were 10-year follow-up data, which is why the Cleveland Clinic experience is so important," Dr Hahn said. Even if short-term outcomes did support the use of SBRT in medically inoperable early lung cancer, "we did not know if patients might develop severe toxicity 5 or 10 years out, because radiation can do that," he elaborated.

"And this study gives us more confidence about the local control achieved with SBRT as well as the absence of side effects 10 years after treatment."

Dr Hahn will soon be moving from Philadelphia: as of January 1, 2015, he will be the head of the Division of Radiation Oncology and chair of the Department of Radiation Oncology at the University of Texas MD Anderson Cancer, in Houston.

Neither Dr Videtic nor Dr Hahn has disclosed any relevant financial relationships.

Chicago Multidisciplinary Symposium of Thoracic Surgery. Abstract 116. Presented October 30, 2014.

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