New research findings demonstrated that patients with different types of early stage non-small-cell lung cancer (NSCLC) can benefit from treatment with stereotactic body radiosurgery (SBRT).

In a presentation on October 4, 2011, at the American Society of Radiation Oncology (ASTRO) 53rd annual meeting held in Miami, FL, USA, Frank Lagerwaard, MD, radiation oncologist at VU University Medical Center (Amsterdam, The Netherlands; www.vumc.com) reported that potentially operable patients with stage I NSCLC who were treated with stereotactic ablative radiotherapy (SABR), which is another term for SBRT, achieved comparable tumor control rates to those treated with the current surgical standard of care. Thirty-three percent of the patients in the study were treated with Varian Medical System’s (Palo Alto, CA, USA) RapidArc delivered on a Novalis TX linear accelerator from Varian and Brainlab, AG (Feldkirchen, Germany).

NSCLC is considered stage I when the tumor is small and has not spread to nearby lymph nodes or distant sites within the body. The standard of care is typically surgery that involves removal of a section of the affected lung. Complications of this kind of surgery can include chest wall pain, atrial fibrillation, wound infections, and pneumonia. “Based on the results of our analysis, SABR appears to be an important option to be considered by all patients presenting with early-stage lung cancer,” said Dr. Lagerwaard, lead study author. “These data also support ongoing randomized clinical trials comparing surgery and SABR in potentially operable stage I NSCLC.”

SABR involves treating the tumor with a targeted high-energy radiation beam. The radiation is intended to damage tumor cell DNA and kill the cancer cell. Complications of SABR in treating NSCLC may include radiation-induced pneumonitis, chest wall complications (pain, rib fractures, chest wall swelling), fatigue, cough, and difficulty breathing.

Dr. Lagerwaard and colleagues retrospectively reviewed records of lung cancer patients treated between 2003 and 2010 to find those who could have been surgical candidates, based on their tumor characteristics and overall health, but who instead received SABR. A total of 177 patients (101 males and 76 females) were evaluated in the study. Medical records demonstrated that at three years’ posttreatment, 93% of SABR-treated patients included in the study did not show local tumor regrowth. This is comparable to previously reported outcomes for patients who received surgery for treatment of NSCLC.

Median overall survival (OS) for the operable patients who received SABR was 61.5 months with one-, three- and five-year survival rates of 94.7%, 84.7 %, and 51.3%, respectively. Thirty-day mortality in patients who received SABR was 0%. This compared favorably to an earlier report by other researchers predicting that, for patients undergoing a lobectomy (removal of the affected lobe of the lung), 2.6% would have been predicted to die within 30 days (based on the Thorascore model, Falcoz PE, 2007).

Forty-two percent of patients in the study reported no early side effects with the SABR treatments. Those that did experience early side-effects experienced fatigue (25%), cough (14%), local chest wall pain (11%), and dyspnea (10%), with some patients reporting more than one side effect. Late side effects of SABR consisted of radiation pneumonitis for which medication was needed in 2% of patients and rib fractures in 3% of patients.

In another presentation, Jeffrey Bradley, MD, associate professor of radiation oncology at Washington University in St. Louis (MO, USA) summarized early results from a prospective phase I/II study to determine the optimal dose of stereotactic body radiotherapy (SBRT) for early-stage non-small-cell lung cancer (NSCLC) located in the central part of the lung, close to the bronchial tree (main airway). The study enrolled 24 patients with stage 1 NSCLC.

According to Dr. Bradley, an earlier study of SBRT for lung cancer did not differentiate between peripheral and central tumors. Patients with both types were enrolled in a prospective dose-escalation study that started by delivering three treatments of 8 Gy each and increased up to 24 Gy at each of three treatments. “From that experience, the investigators described excessive toxicity for tumors located within 2 cm of the proximal bronchial tree and warned of potential toxicity,” Dr. Bradley said. “Based on that report, we launched this prospective phase I/II study in an effort to help determine a viable treatment protocol for centrally located early-stage lung cancers. The Radiation Therapy Oncology Group [RTOG] followed along and also has a prospective dose escalation study ongoing for this population.” The RTOG is a US clinical cooperative group funded by the National Cancer Institute (Bethesda, MD, USA) to conduct cancer treatment research.

Each patient enrolled in Dr. Bradley’s study received five SBRT treatments. Five patients received a dose of 9 Gy units per treatment; six received 10 Gy each time; six received 11 Gy each time; and five received 12 Gy each time. The overall primary tumor control rate was 95.5%.

Sixteen of the 24 patients remain alive with a projected three-year overall survival rate of 45.7%, a projection that is based on the published data on this medically inoperable group. Treatment-related toxicities remained tolerable at doses up to 12 Gy, with only one patient developing a grade 3 pneumonitis. The trial will proceed to phase II to measure efficacy at a dose level of 5 x 11 Gy.

“To date, local tumor control has been excellent for the patients in this trial,” said Dr. Bradley. “This study, along with others, will help determine a viable SBRT treatment protocol for centrally-located early-stage lung cancer, which could provide a treatment option for patients with this inoperable disease.”

“The findings from these two studies show the importance of continuing to evaluate new treatments for lung cancer. Advancements in radiotherapy have the potential to help treat early-stage lung cancer without some of the complications of surgery, and they appear to offer inoperable patients a viable treatment option,” said Dow Wilson, Varian’s chief operating officer.

Varian’s high-energy linear accelerators, and the company’s RapidArc radiotherapy technology, are indicated to provide stereotactic radiosurgery and precision radiotherapy for lesions, tumors, and conditions anywhere in the body when radiation treatment is indicated. While clinical studies such as those highlighted here may support the effectiveness of Varian’s technology when used for radiotherapy or radiosurgery, individual results may vary.

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