695P - Assessment of the utility of CT scans in the long-term follow-up of metastatic non-seminomatous germ cell tumours (mNSGCT): The Late CT study

Background

Most patients (pts) with mNSGCT are cured by platinum based chemotherapy. A small proportion relapse usually in the first two years (yrs) and late relapses can occur with an estimated rate of up to 0.5-1% per yr. Late relapses, often due to a chemotherapy resistant residual teratoma differentiated highlights the importance of early detection to allow earlier surgical interventions and improve prognosis. We hypothesized that screening mNSGCT pts with ‘late CT scans’ could detect residual/recurrent disease at a treatable stage and reduce the risk of late relapses.

Methods

This prospective diagnostic study recruited pts with mNSGCT (RMH stage II-IV) who completed treatment 5-10 yrs prior to entry and had a CT scan with no evidence of disease following chemotherapy at least 3 yrs prior. All pts underwent a CT scan of the thorax, abdomen, and pelvis on entry. Pts with negative CT had annual follow up and a repeat CT at 5 yrs. Pts with equivocal CTs had a repeat CT in 6 months. The primary endpoint was the rate of CT-detected abnormalities due to NSGCT on initial scan.

Results

195 pts were recruited between 2006 and 2021, the no. for final analysis was 192. Median (IQR) age at consent: 36 (31-43) yrs. 93% had a testicular primary. Primary histology: mixed GCT (47%), embryonal (31%). Primary chemotherapy: BEP (76%), CBOP-BEP (14%). 90 (47%) underwent surgery: mature teratoma (52%), necrosis/fibrosis (24%). 187 pts underwent initial CT: normal 167, equivocal 14, abnormal 6. Recurrence was confirmed in 4 pts with abnormal CT and 1 pt with equivocal CT. The rate of CT-detected abnormality on initial scan: 5/187, 2.67% (95% CI 0.87, 6.13), false positive 33%. Of 182 pts who were recurrence-free on initial CT, 2/182 had a recurrence within the study period, 1.1% (95% CI 0.13, 3.91). 122 pts underwent 5-year CT, equivocal 7/122 but no confirmed recurrence. Of five pts with a recurrence on initial CT, two had at least a further recurrence. The 5-yr overall survival was 97% (95% CI 92-99) and the recurrence-free survival was 99% (95% CI 95-100).

Conclusions

A late follow-up CT at 5 yrs post-treatment detects a small but significant number of recurrent germ cell tumours. Recurrence after a negative late CT is low and further imaging may not be warranted.

Clinical trial identification

CCR2577 United Kingdom.

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.