Functional Imaging in Lung SBRT

Stereotactic body radiation therapy (SBRT) is becoming a new standard for unresectable lung
metastases and primary lung cancers.

However, it is becoming increasingly common for patients to undergo multiple courses of lung
SBRT to synchronous and/or metachronous lung lesions. Further, the indications for SBRT are
being expanded to patients who have very poor pulmonary function such as FEV1 < 0.5 L or DLCO
< 35% predicted, who have large tumors (>3 cm), or who have centrally located lesions that
abut great vessels and mainstem bronchi. Little is known about the safety of such treatments,
especially the impact on pulmonary function, quality of life, and on functional changes
within the lung itself. Radiation dose constraints and capturing functional changes on
imaging are not well studied in this setting.

The current study aims to evaluate the utility of advanced imaging to measure lung function
prior to and after treatment and to assess the feasibility of using this data to adapt SBRT
planning. SPECT/CT will be used to measure ventilation and perfusion changes while. CT
ventilation scans will be used to correlate functional changes observed on diagnostic
SPECT/CT. Dynamic contrast enhanced MRI (DCE-MRI) will also be used to explore local vascular
changes in the treated tumor. In patients whose tumors lie close to the heart, cardiac MRI
will be used to investigate whether high doses of radiation per fraction are associated with
changes in cardiac function. These imaging modalities may be used to potentially predict
toxicity and patient response with the ultimate goal of prospectively adapt dose to
individual patient and tumor characteristics. Lung function prior to and post-treatment will
also be measured as a correlate of functional imaging changes. Identifying areas of the lung
that are sub-functional or low-functioning may offer an opportunity to adapt stereotactic
ablations that spare functional lung thereby making SBRT treatments to higher risk patients
safer.

Inclusion Criteria:

- Patients receiving SBRT lung treatment and who have any one of the following high risk
features:

- Lung lesion > 5 cm

- DLCO < 35%

- FEV1 < 0.5 L

- Central lung tumors (defined as within 2 cm from the proximal bronchial tree)

- Tumors that abut the great vessels, trachea, spinal cord, or esophagus

- Prior lobectomy or pneumonectomy

- Prior lung radiation (SBRT or conventional definitive lung radiation)

- Patients must be 18 years of age or older

Exclusion Criteria:

- Patients who have received targeted agents or systemic potentially radiosensitizing
chemotherapy within 2 weeks of lung SBRT start

- Pregnancy or lactation

- Unable to tolerate MRI without anesthesia

- Inability cooperate with the scans