734P - Primary retroperitoneal germ-cell tumours (pR-GCT): Evaluation of treatment outcomes of an international collaboration (PRIMERE study-IGG05)

Background

pR-GCT corresponds to the clinical case of retroperitoneal ascertained GCT without radiological evidence of primary testicular tumor and accounts for up to 40 % of extragonadal GCTs. An occult primary testicular tumor is often missed at diagnosis. Treatment modalities and outcomes have not been specifically addressed, preventing robust recommendations. We performed an international call to assess prognosis of treatment outcomes of these patients.

Methods

Clinical, pathological and treatment data pts with pR-GCT between 04/1988 and 01/2022 were retrospectively collected across 4 referral centers. Kaplan Meier methods, univariable and multivariable Cox regression models (MCRMs) were used.

Results

Ninety-nine patients (median age 37 yrs - IQR: 29-45) were collected. Ninety-three (94%) had histological diagnosis by biopsy or primary retroperitoneal lymph-node dissection (RPLND): 60 (62.5%) had non-seminomatous pR-GCTs (pR-NSGCTs) and 33 (34.4%) had seminomatous pR-GCTs (pR-SGCTs). IGCCCG prognostic allocation was possible in 91 pts: 34 (35.8%) were good, 23 (24.2%) intermediate and 34 (35.8%) poor risk, respectively. All pts underwent cisplatin-based chemotherapy, usually BEP regimen (94.9%). After chemotherapy, 25 (25.3%) pts underwent orchiectomy: viable tumor was present in 8 (32%), burn-out lesions in 6 (24%) and no lesion in 11 (44%) cases. After a median follow-up of 45 mos (IQR:15-90), the 5-years OS was 58%, being 85% in case of pR-SGCT and 46% in case of pR-NSGCT. According to IGCCCG classification 5-years OS was 83.3% for good, 57% for intermediate and 42% for poor risk patients, respectively. No difference in term of OS (60% vs 56%, p-value 0.81) was observed between patient who had or not radical orchiectomy. At MCRMs only IGCCCG poor risk category (HR 3.2, CI: 1.18-8.84, p-value 0.02) was independent predictors of a worse OS.

Conclusions

Eventually, a significant proportion of pts with a pR-GCT had a misclassified primary testicular tumor. 5 yrs-OS according to IGCCCG classification is worse than expected. The role of a surgical exploration of the suspected primary tumor remains controversial and the existence of a real category of p-GCT cannot be excluded.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

Patrizia Giannatempo.

Funding

Has not received any funding.

Disclosure

P. Giannatempo: Financial Interests, Personal and Institutional, Advisory Board: Pfizer, Astellas, MSD, Merk, Janssen; Financial Interests, Personal and Institutional, Local PI: AstraZeneca. All other authors have declared no conflicts of interest.