Abstract 129P
Background
SBRT for lung cancers located near the chest wall (CW) may result in local pain which is not always attributed to the SBRT. Longitudinal FDG PET (PET) images were investigated to asses PET’s role in diagnosing such pain.
Methods
Clinical records and PET images of patients (pts) treated with SBRT from 2009-2023 were reviewed. Pts were divided into those whose tumors were close (or distant) to the CW, defined as the Planning Target Volume touching (or not) the CW. Post-SBRT PET images obtained to assess tumor response after SBRT were exported to a commercial tool measuring SUV mean, SUV maximum and the Total Lesion Glycolysis (TLG) of the visible manually contoured hypermetabolic CW regions corresponding to the SBRT location. SUV metrics were compared between symptomatic (sympt) vs. asymptomatic (asympt) pts, using t-tests. For pts without apparent hypermetabolic regions, the CW adjacent to the SBRT location was contoured manually at 3 consecutive CT slices.
Results
There were 108 pts with Stage I lung cancer who received SBRT: 73 with tumors near CW and 56/73 with post-SBRT PET images (mean 1.8, range 1-13 PET scans per pt), comprising the analyzable population. Median age was 73 (range: 60-89); 64% were females and median follow-up time (FU) was 32 months (mo) (range: 3-169). Eleven pts (19.6%) reported CW pain near the SBRT location which could not be explained otherwise; 9/56 pts (16%) developed rib fractures and 5 pts with long FU (median 66 mo, range: 60 to 169) had CW heterotopic ossification. There was a significant difference in SUV mean between sympt vs. asympt pts (1.7 ± 0.44 vs 1.34 ± 0.44, respectively, p value 0.02), but not in SUV max (2.65 ± 0.87 vs. 2.08 ± 1.02, respectively, p value 0.095). No significant difference was observed in the TLG between sympt vs. asympt pts (22.66 ± 12.44 vs. 27.26 ± 36.9, respectively, p value 0.69).
Conclusions
This is the first cohort study to quantitatively demonstrate a significant (p=0.02) difference in CW PET signal for patients who did or did not develop CW toxicity after SBRT. PET is a valuable diagnostic tool for visualizing symptomatic post-SBRT CW injury (“CW myositis”), clarifying nonspecific CW pain, and possibly providing an early predictor for CW injury.
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.