AT WCLC 2016

VIENNA (FRONTLINE MEDICAL NEWS) – Stereotactic body radiotherapy (SBRT) proved too toxic for many of patients recruited into a multinational phase II trial with centrally-located lung tumors.

The majority of patients experienced some type of adverse effect, with 28% experiencing serious (grade 3-5) adverse effects.

“Our major concern now is that we had six cases of grade 5 bleedings,” Karen Lindberg, MD, said at the World Conference on Lung Cancer. “Tumor location seems to be a risk factor for bleeding,” she added, with five of the six cases seen in patients who had tumors close to a main bronchus (group A). The other case was in patient who had tumors close to a lobular bronchus (group B).

“The classical definition of a centrally-located lung tumor is a tumor residing within or touching an imaginary zone 2 cm around the proximal bronchial tree,” explained Dr. Lindberg of Karolinska University Hospital and the Karolinska Institutet in Stockholm, who presented the first results of the Nordic HILUS Trial.

“When we designed this study we wanted to look at very centrally located tumors, so we tightened up this definition to look at tumors that occurred within 1 cm around the proximal bronchial tree,” she said at the meeting, which was sponsored by the International Association for the Study of Lung Cancer.

During the trial, SBRT was to be delivered at a dose of 7 Gray (Gy) in 8 fractions at 65%-75% isodose lines to ultra-centrally-located tumors. Dose constraints were stipulated for tumors situated very close to the spinal cord, contralateral main bronchus, and trachea, with some dosing recommendations on reducing the dose delivered to tumors that were ipsilateral to the main bronchus, or very close to the esophagus or heart.

A total of 74 patients with centrally-located, locally progressive tumors, which were less than 5 cm in size and due to non–small-cell lung cancer (NSCLC) or metastatic lung disease from another solid tumor, were recruited. Patients had to have a good performance status and life expectancy of 3 months.

Patients with brain metastases or tumors that reached through the wall of a main bronchus were excluded as were those who were taking any concomitant systemic therapy.

The mean age of the recruited patients was 71 years; 58 (78%) had NSCLC, of which 20 (27%) had adenomas and 19 (26%) had squamous cell cancers. Of those with secondary lung tumors, eight (11%), had primary renal cell carcinoma and four (5%) had colorectal cancer.

After a follow-up of 18.6 months, 31 (42%) patients had died.

The most common adverse events reported were grade 1-2 dyspnea, cough, and fatigue. However, there was a high rate of grade 3 (dyspnea, fatigue, pain, pneumonitis, and heart rhythm disturbance), 4 (pain, lung infection, fever, heart rhythm disturbance, fistula, and pneumothorax) and 5 toxicities (pneumonitis and bleeding).

Bleeding often occurred without warning and had an acute onset and toll.

Seven patients (six in group A and one in group B) may have suffered grade 5 side effects; six patients experienced lethal hemoptysis after a median of 15.5 months (2.5-21 months) and one patient suffered from a lethal pneumonitis 5 months post study treatment. The reintroduction of TKIs may also have played a role, Dr. Lindberg suggested.

SBRT for early stage NSCLC is very effective and “generates outstanding tumor control”, said Feng-Ming Kong, MD, of Indiana University, Indianapolis, who was invited to comment on the findings.

Most studies of SBRT have looked at peripherally-located tumors, however, so the study by the NORDIC Study Group provides valuable information on a more centrally-located approach. The big question of course is what caused the bleeding.

“What percentage of TKI patients had bleeding and how many of them had a TKI without bleeding?” Dr. Kong asked. Other questions around dosing remain: How much radiation was delivered to the great vessels such as the pulmonary artery, and how much of the dose hit critical structures? And, were tumors invading the pulmonary artery?

“SBRT may be applied for centrally-located tumors safely with other prescription regimens, she suggested, such as 10-11 Gy given in 5 fractions. That is assuming that “the dose limits of normal tissues are strictly controlled and the patients are carefully selected to exclude T4 diseases for adjacent organ invasion.”

The NORDIC SBRT Study Group conducted the study. Dr. Lindberg had no conflicts of interest to disclose. Dr. Kong has received research grants from the National Cancer Institute (part of the National Institutes of Health) and speakers honorarium and travel support from Varian Medical.