Detection of Relapse by Low-dose Computed Tomography During Surveillance in Stage I Testicular Germ Cell Tumours

Background: Standard-dose computed tomography (SDCT) scans are associated with radiation exposure during stage I testicular cancer surveillance.

Objective: To evaluate low-dose CT (LDCT) for clinical use.

Design, setting, and participants: In this single-arm prospective study, patients on surveillance for stage I testicular germ cell tumour underwent SDCT and LDCT scans on their first visit after enrolment. The adequacy of LDCT image quality was assessed for subsequent use. Patients were followed with LDCT only and suspected relapse was confirmed by SDCT.

Outcome measures and statistical analysis: We assessed whether initial LDCT scans were of sufficient quality for routine clinical use. We compared mean differences in nodal size at relapse between LDCT and SDCT using a one-sample paired t test. The relapse free-rate was calculated using the Kaplan-Meier method.

Results and limitations: Of 257 patients, one was excluded because of inadequate image quality. At median follow-up of 5.25 yr, 35 patients had relapsed, 33 with retroperitoneal lymphadenopathy. The 2- and 5-yr relapse-free rates were 89.5% and 85.3%, respectively. The mean size of retroperitoneal nodal relapse was 17.3 and 17.5mm on the short axis, 23.2 and 22.7mm on the long axis, and 26.1 and 26.7mm on craniocaudal length for LDCT and SDCT, respectively. The mean difference between LDCT and SDCT was 0.14mm (p=0.55) short axis, -0.54mm (p=0.092) long axis, and -0.51mm (p=0.086) length. A limitation was the lack of a control arm.

Conclusions: LDCT image quality was adequate for clinical use, and retroperitoneal nodal relapse was detected with minimal differences seen between LD and SDCT. LDCT can be safely adopted and will decrease overall radiation exposure in stage I germ cell tumour surveillance.

Patient summary: We studied the use of low-dose computed tomography scans for detecting testicular cancer recurrence in lymph nodes of the abdomen and pelvis and found that they were safe, effective and would potentially reduce overall X-ray exposure. This trial is registered at ClinicalTrials.gov as NCT03142802.