Patients with locally advanced cervical cancer (LACC) are treated with external beam radiotherapy (ERBT), concomitant chemotherapy and brachytherapy (BT). Pathological nodes in the pelvis and para-aortic region are often boosted by ERBT. However, high dose volumes around the nodes may damage nearby organs at risk. Coverage probability planning (CovP) is a new method, allowing for a simultaneous integrated boost (SIB) with a central nodal hot spot and a steep extra nodal dose gradient towards the surroundings (1). CovP is currently being used in the multicenter prospective EMBRACE II study (2) and has been used routinely at AUH since 2015 (3). The aim was to analyze the long-term recurrence pattern of boosted nodes for patients treated at AUH by use of CovP based SIB.

135 consecutive patients with LACC treated between Nov 2015-April 2019 were analyzed. Of these 60 (44%) were included in EMBRACE. Diagnostic nodal work up included FDG PET-CT and MRI. All patients were discussed in a multidisciplinary forum. Nodes were considered pathological based on signal, size and morphology. Surgical nodal staging was not used. EBRT consisted of whole pelvis 45 Gy/25 fx +/- para-aortic irradiation and SIB to 55 Gy/25 fx or 57.5 Gy/25 fx according to the expected BT contribution (2). Concomitant weekly cisplatin was given routinely unless curtailed by age, comorbidity, performance status or toxicity. 89/135 (66%) received weekly cisplatin but only 50/135 (37%) achieved 5 courses. MRI guided adaptive BT was performed in all patients. The EMBRACE II planning aims (2) were used for both EBRT and BT. Nodal follow-up was based on routine MRI and PET-CT at 3 months and MRI 12 months after treatment. Additional imaging and biopsy were performed at suspicion of any recurrence.

Pathological nodes on imaging at diagnosis was found in 66/135 (49%) with a range of 1-7 nodes per patient. Total number of nodes treated with SIB was 184 of which 20 (11%) were para-aortic. 91% of the nodes were PET-CT positive. Median follow-up time was 20 months. Six patients had SIB node recurrence. In total 7 (4%) SIB nodes recurred resulting in a 3-year actuarial SIB control rate of 93%. All recurrent SIB nodes were located in the pelvis and all were PET-CT positive at diagnosis. Median nodal volume was 2.0 and 4.2 cm³ in controlled and recurrent SIB nodes, respectively. Only one of the patients with a recurring SIB node had received Cisplatin.

Despite a low completion rate of concomitant cisplatin, this study demonstrates a satisfying long-term control rate of pathological nodes treated by CovP based SIB in unselected patients with LACC. The results lend support to the utilization of CovP for SIB of both pelvic and para-aortic nodes. Confirmation is awaited from the EMBRACE II study.

References

1) Ramlov, Radiother Oncol, 2017, 123:158-163

2) Pötter, Clin Transl Radiat Oncol, 2018, 9:48-60

3) Lindegaard, Acta Oncologica, 2017, 56:1479-1486