Early PET/CT scans for assessing treatment responses of non-small cell lung cancer for SBRT boost: what to do with scans from multiple scanners.

Chemoradiation remains the standard of care for the nonsurgical treatment of advanced non-small cell lung cancer (NSCLC) but local recurrence rates of 30-40% are documented. We examined the early PET/CT responses of NSCLC treated with standard chemoradiation in a prospective single institutional trial of early 18F-2-deoxy-D-glucose-PET/CT scans to help define patients appropriate for dose escalation with SBRT. 48 patients with stage IIA, IIB or IIIA-B NSCLC with no or non-bulky (</= 3.0 cm) lymphadenopathy were included. Approximately one month following chemoradiation, PET-CT was performed to assess responses. Since many patients came from outside facilities, the ability to directly compare pre- and post therapy PET/CT SUV values is compromised. Thus, patients had their pre- and post-chemoradiation PET/CT SUV's assessed where possible, but also reviewed in a blinded manner by two experienced nuclear medicine physicians who scored the results on a subjective scale of FDG uptake to assess treatment responses. A high level of agreement was found between the reading nuclear medicine physicians: 0.76 (95% CI of 0.6 to 0.92). Disease progression occurred in 16% of scans including new metastatic or regional failures. 77% of patients had significant improvement in FDG uptake in the primary tumor but only 4.2% had complete resolution. Mediastinal adenopathy had resolved or significantly improved in 90%. This good, but not complete reduction of FDG uptake in the primary tumor suggests that it may be an appropriate target for local intensified radiation boost.