Pediatric Mesothelioma Tumors: The European Expert Group Contribution.

Background and Aims: In adults with mesothelioma, cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (CRSHIPEC) is a standard of care in limited tumor, but long-term survival is very uncommon. Very little is known about the characteristics of this tumor in the pediatric population. Methods: The EXPeRT group of very rare pediatric tumors reviewed retrospectively children and youths (≤21 year) diagnosed in Europe with mesothelioma tumors treated between 1987 and 2018. Results: Thirty three patients were identified, 14 males and 18 females. Only one exposure to asbestos was documented. Primary tumor was located into the peritoneum (23 patients), pleura (2), vagina (2), pericardium (1), and in multiple sites (5). Histology was multicystic peritoneal mesothelioma (MCPM; 6 patients; median age 14.1year, range 2.2-21.1) or malignant (27 patients; median age 13.4 year, range 0.2- 18.7): epithelioid (21), biphasic (4) and unspecified (2). All patients with MCPM are alive despite 4 peritoneal relapses, after surgery (5 patients) and CRS-HIPEC (1pt). Metastasis at diagnosis were present in 9/27 patients with malignant mesothelioma. Among them, first line treatment was heterogeneous: preoperative chemotherapy (14 cases), exclusive surgery (3 cases), exclusive chemotherapy (5 cases), adjuvant chemotherapy (3 cases) or palliative (2 cases). Response rate to cisplatin-pemetrexed was 50% (6/12 cases) with no response to other regimens (0/12 cases). Two patients have long term tumor controlwith targeted therapy. CRS-HIPEC was performed in 19 patients (upfront 3 cases, after neoadjuvant therapy 12 patients, or after tumor progression 6 cases, including 3 twice). After a median follow-up of 6.7y (range, 0-20), 5 year overall and event free survivals are respectively 82.3% (95%IC 67.8-99.9) and 45.1% (95%IC 28.4-71.7). Conclusions: Pediatric Mesothelioma is exceptional and seems to be different from its adult counterpart with few asbestos exposures and a better outcome. Cisplatin-pemetrexed regimen showed some efficacy. Relapses could be salvaged with active therapy including CRS-HIPEC. Targeted therapy should be considered.