18F-fluorodeoxyglucose PET-CT-guided pelvic chemoradiation therapy using helical tomotherapy for locally advanced carcinoma cervix without para-aortic nodal disease: Clinical and patient-reported outcomes from a prospective phase 2 study.

Introduction: Locally advanced carcinoma cervix (LACC) is a heterogeneous disease with variable combinations of primary tumour extensions with or without nodal involvement. Metabolic information from 18 fluro-deoxyglucose positron emission tomography combined with contrast-enhanced computerized tomography (FDG PET-CT) may potentially augment treatment decision-making for LACC. This study ascertained FDG-PET CT influence on chemoradiation therapy (CTRT) decisions in LACC. We report oncologic and patient-reported outcome measures (PROMs).

Methods: FDG PET-CT scans were reviewed independently by two nuclear medicine specialists and two radiation oncologists. Pelvic CTRT plan digressions were documented and therapy was adapted accordingly. Pelvis radiation (50 Gy/25#/5 weeks) using tomotherapy with weekly cisplatin was used in node-negative disease. Dose-escalated simultaneous integrated boost (SIB) 60 Gy/25#/5 weeks was delivered to involved pelvic nodes. All received brachytherapy. Post-treatment PET-CT scans were at 6 months. Functional assessment of cancer therapy scores were calculated at baseline, treatment completion, 3 months, 1 year and 3 years.

Results: Between November 2015 and January 2018, 85 patients were screened, and 77 consented. Extrapelvic disease was seen in 12 (16%) patients (9 para-aortic nodes, 2 distant metastases and 1 synchronous carcinoma breast); 60 patients were included in the final analysis. Decision changes were seen in 10/77 (13%) screened, 8/60 (13%) included and 32 (53.3%) received SIB. Post-treatment, 27 (45%) had grade 2 GI/GU/GYN toxicity, one (2%) had grade 3 GI and five (8.3%) had grade 3 neutropenia. At median follow-up of 54.2 months (95% CI 52.8-58.3), 5-year local failure, pelvic nodal and para-aortic nodal-free survival were 86.8% (95% CI 78.0-96.6), 85.2% (95% CI 76.1-95.3) and 85.2% (95% CI 76.2-95.4). Functional assessment of cancer therapy trial outcome index (FACT TOI) improved by 10.43 at 3 months with no further decline. Grade 3 toxicity was noted for abdominal pain in one (1.7%), cystitis in four (6.7%) and lymphoedema in one (1.7%) at 5 years.

Conclusion: PET-CT resulted in major decision changes in 13%. PET-adapted CTRT was associated with acceptable toxicity, encouraging long-term survival and improvement in PROMS.