No systematic synthesis of all cases of spontaneous tumor lysis syndrome (STLS) in adult patients with solid tumors is available to date. Herein, we aim to recognize specific STLS characteristics and parameters related to a worse prognosis. We conducted a systematic search for randomized controlled trials, cohorts, case-control studies, and case reports. The primary endpoints were death and the need for renal replacement therapy (RRT) due to STLS. We estimated crude odds ratios (ORs) with 95% confidence intervals (95%CI) via univariate binary logistic regression. We included one cohort of 9 patients and 66 case reports of 71 patients [lung cancer 15(21.1%)]. Regarding the case reports, most patients [61(87.1%)] had metastatic disease [liver 46(75.4%)], developed acute kidney injury [59(83.1%)], needed RRT [25(37.3%)], and died due to STLS [36(55.4%)]. Metastatic disease, especially in the liver [p= 0.035; OR (95%CI): 9.88 (1.09, 89.29)] or lungs [p= 0.024; 14.00 (1.37, 142.89)], was significantly associated with STLS-related death compared to no metastasis. Cases resulting in death had a significantly higher probability of receiving rasburicase monotherapy than receiving no urate-lowering agents [p= 0.034; 5.33 (1.09, 26.61)], or the allopurinol-rasburicase combination [p= 0.023; 7.47 (1.40, 39.84)]. Patients receiving allopurinol were less likely to need RRT compared to those not receiving it or those receiving rasburicase. In conclusion, current anecdotal evidence demonstrated that metastatic disease, especially in the liver and lungs, may be associated with STLS-related death compared to no metastatic status. Careful surveillance of high-risk cases within larger studies is essential to identify markers predicting morbidity or mortality.Supplementary InformationThe online version contains supplementary material available at 10.1007/s12032-023-02108-4.