How hot is too hot? Use of PET to evaluate response to radiation therapy for patients with cervical cancer

Purpose This study sought to determine the relationship between cervical cancer recurrence and post-treatment change in standardized uptake value (SUV) of ¹⁸ F-2-fluoro-2-deoxy-D-glucose-positron emission tomography (FDG-PET) in the cervix and lymph nodes. Methods A retrospective study of patients who received curative intent radiation therapy for biopsy-proven stage I-IVA locally advanced cervical cancer from 2009–2021 was performed. Percent differences in SUVs at the cervix and the most avid and distant lymph nodes were calculated from pre- and post-treatment scans and used as independent variables for analyses. The primary outcome was recurrence rate, and secondary outcomes were overall and progression-free survival. Results 55 patients met eligibility criteria. Recurrence rate was 27% (15/55); of these, 33% had local recurrence (5/55) and 67% had distant recurrence (10/55). Median percent decrease of cervical SUV after treatment in those with and without recurrence was similar (71.4 vs 68.8, p = 0.89); this remained consistent when analyzing those with local recurrence only (70.5, p = 0.95). When the percent decrease in cervical SUV was examined in intervals (< 25%, 25–50%, 50–75%, > 75%), this was also not predictive of local (p = 0.91) or overall (p = 0.75) recurrence. Median percent decrease at the most avid and distant lymph node in those with and without recurrence was not significantly different (p > 0.05). Neither change in cervical nor lymph node SUV were associated with overall or progression-free survival. Conclusion Changes in SUV after treatment are likely not a reliable stand-alone marker for predicting recurrence or survival in locally advanced cervical cancer after treatment with radiation therapy.