Introduction/Background Para-aortic lymph nodes involvement in locally advanced cervical cancer is a determining factor in patient´s treatment as it determines radiotherapy field. PET/CT is used to assess lymph node involvement at this level, although it is not exempt from false negatives. Our aim is to compare PET/CT with para-aortic (PA) lymphadenectomy, in order to assess the false negative rate of this test, as well as the factors associated with a greater probability of false negatives.

Retrospective descriptive study Cases of locally advanced cervical cancer with negative PET/CT that underwent para-aortic lymphadenectomy from 2018 to 2022 were collected. During recruitment period, a new PET/CT technique was developed. Outcomes of both types of PET/CT were compared.

Results A total of 11 patients underwent radiological node staging with the first type of PET/CT and 12 patients with the new one. Mean age was 52,09 (±15,3). Epidermoid was the most frequent subtype (65,2%). Mean time between PET/CT and surgery were 21.77 days (±10.53). Mean number of lymph nodes obtained were 12.48 (±5.10). 91.3% (21) of patients had a negative pathological result and 8.7% (2) were positive (PET/CT false negatives). One patient presented macrometastasis and one patient isolated tumor cells. Negative predictive value of first type of PET/CT was 0.90 and that of the new one was 0.91. One of false negative cases had a unilaterally positive pelvic PET/CT and the other bilaterally.

Conclusion Our false negative rate of PET/CT was similar to that described in literature. No significant differences between the two types of PET/CT were observed. Pelvic lymph node involvement seems to be associated with a higher false negative PET/CT. After analyzing our data, we don´t have enough evidence to avoid performing PA lymphadenectomy in these patients as routine, having to individualize the risk-benefit in each case.