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MINI 04 - Clinical Care of Lung Cancer (ID 102)
- Event: WCLC 2015
- Type: Mini Oral
- Track: Treatment of Advanced Diseases - NSCLC
- Presentations: 1
MINI04.06 - During-Treatment PET Metabolic Tumor Volume (MTV) Instead of FDG Activity Is Predictive of Survival in Patients with Non-Small Cell Lung Cancer (ID 3174)
16:45 - 18:15 | Author(s): T.S. Lawrence
We have previously reported that tumor reduces in activity and volume during the course of radiotherapy (RT), and such changes were correlated with post-treatment “tumor response”, known as a significant factor for overall survival in patients with non-small cell lung cancer (NSCLC). This study aimed to determine whether the metabolic activity or metabolic tumor volume (MTV) obtained from the during-treatment FDG-PET is predictive of overall survival in NSCLC.
Patients with stage I-III NSCLC enrolled in prospective studies with during-treatment FDG-PET were eligible for this study. All patients were treated with a definitive course of RT + chemotherapy. FDG-PET/CT scans were acquired within 2 weeks before RT (pre-RT) and at about two thirds of the total dose delivered (during-RT). PET-MTVs were delineated by a tumor/aorta ratio of 1.5 autosegmentation combined with manual editing based on CT anatomy, as previously described (Mahasittiwat et al, 2013). FDG-activity was measured as maximum standard update value (SUVmax) and the average activity (SUVmean) of the defined MTV. Total lesion glycolysis (TLG) was computed as the product of MTV and SUVmean. CT gross tumor volume (CT-GTV) were also delineated in a consistent manner. Data are presented as mean (95% confident interval). P<0.05 is considered to be statistically significant.
A total of 129 patients with a minimum follow-up of 24 months (for surviving patients) were included in this study. The majority of subjects were male (73%), white (96%), current or former smokers (87%) with an average age of 67 years (range 45-92). Seventy-nine percent were treated with chemotherapy in combination with RT (dose range 45-90 Gy). Of the pre-RT PET parameters, neither SUVmax nor SUVmean was significant, while CT-GTV (P=0.03), PET-MTV (p=0.008), and PET-TLG (p=0.005) were all significant for overall survival. After 2/3 treatments were delivered, the mean SUVmax, SUVmean, CT-GTV, PET-MTV, and PET-TLG all decreased significantly (P<0.001) and remarkably (more than 30% reduction), with the PET-MTV showing the greatest extent of reduction. During-RT SUVmax or SUVmean were not significantly associated with overall survival, either as continuous variables or as binominal variables (split from median). While during-RT CT-GTV was a significant factor for survival (P=0.04), yet during-RT PET-MTV and PET-TLG as continuous variables were not. However, patients with during-RT PET-MTV values greater than the median had significantly shorter median survival (21 months, 95%CI: 12.1-32.0) than those of below the median (38 months, 95%CI: 29.0-89.9, p=0.01). The absolute reductions in SUVmax or SUVmean or CT-GTV were not, but changes of PET-MTV and PET-TLG during-RT were significantly associated with overall survival. Smaller reductions from Pre-RT to during-RT were associated with an increased risk of death for PET-MTV (HR=1.003, 95%CI: 1.001–1.006, P=0.01) and PET-TLG (HR=1.001, 95%CI: 1.000–1.001, P=0.02), respectively.
MTV instead of SUV during the course of RT are significantly associated with overall survival in patients with NSCLC. Larger MTV during-RT may lead to worse survival. RTOG1106/ACRIN6697 is ongoing to adapt radiation therapy plan to give higher dose to residual PET-MTV during-RT to improve tumor control and overall survival.
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