A secondary analysis of FDG spatio-temporal consistency in the randomized phase II PET-boost trial in stage II-III NSCLC.

Abstract

PURPOSE

FDG-PET scans have shown spatial consistency in NSCLC patients before and following chemoradiotherapy, implying radioresistance. We hypothesized that patients, who received FDG-PET redistributed dose painting, would demonstrate reduced spatial consistency when compared to registered patients or to escalated dose treatment.

CONCLUSION

FDG redistributed boosting did not reduce FDG spatial consistency from pre-treatment to post-treatment, which was highly variable among patients. The study found high numbers of patients with lung inflammation after treatment.

METHODS

Stage II-IIIB, inoperable NSCLC patients were randomized in a phase II trial (NCT01024829) to (chemo)radiotherapy of either homogeneous boosting to the primary tumor, or redistributed inhomogeneous boosting to the GTV subvolume (FDG-SUV > 50% SUV_max). Patients who could not be boosted (≥72 Gy) received 66 Gy in 24 fractions. Spatial consistency of pre-treatment and post-treatment (3 months) FDG-PET scans was measured by various overlap fraction thresholds.

RESULTS

66/82 patients analyzed received randomized treatment in the trial. Thresholds of 50% SUV_max pre-treatment and 70% SUV_max post-treatment yielded a median overlap fraction of 0.63 [interquartile range: 0.15-0.93], with similar results for other thresholds. No significant differences were found among overlap fractions of the treatment groups. A high incidence of FDG-uptake in normal lung (grade-1 pneumonitis: 73%) was found post-treatment.