Endocrine Abstracts

Introduction: Malignant pheochromocytoma (MPheo) is diagnosed by the presence of invasion of adjacent structures or distant metastasis. Predictive factors of malignancy for pheochromocytoma (Pheo) are not well known.

Material and methods: We retrospectively analyzed clinical, biochemical, radiological characteristics as predictors for malignancy in patients with Pheo in two Spanish tertiary hospitals during the past 35 years. We also evaluated time of recurrence, most frequent locations of metastatic lesions, and surgical and other therapeutic modalities.

Results: We reviewed 80 patients diagnosed with Pheo (8 MPheo, 10%). Metastatic disease/invasion of adjacent structures was present in 4/8 at the time of diagnosis, and become evident in 4/8 after surgical removal of the primary tumor, within 7 years (range 1–8). Age at diagnosis was similar in both groups (MPheo 52.1yrs; range 15–73 vs Pheo 51.5yrs, range 13–76; (P=0.481)). Males comprised 62.5% versus 40.8% of the MPheo and Pheo group, respectively. (P=0.216). Prevalence of hypertension was similar in both groups [MPheo, 3/8, 3/8 (37.5%) and non-MPheo 32/72 (44.4%); P=0.109]. All 8 MPheo patients had elevated catecholamines (urinary and/or plasma) with an average of 5.6 times the reference value. MIBG imaging was performed in 4/8 patients, and all of them had positive scans. MPheo was unilateral in 7/8 patients; the patient with bilateral MPheo was diagnosed of MEN2a. Tumor size was significantly higher in MPheo than in non-MPheo patients (10.1 vs 5.7 cm, P=0.038). Metastatic lesions were found in the liver (n=4), bone (n=3), vascular (n=3), and distant lymph node (n=2). Resection of the primary mass was performed in 2 out of 4 patients with initial metastatic disease. 2/8 MPheo patients underwent surgery of metastatic lesions. Non-surgical treatment was also implemented in 6/8 (75%), 5/6 received high-dose MIBG and 1/6 chemotherapy (vincristine, dacarbazine and cyclophosphamide). Evaluation of the best overall response according to the RECIST1.1 Criteria was conducted in 6 out of 8 MPheo. Complete response was achieved in 2/6 patients (one treated with chemotherapy and another with high-dose MIBG; cumulative dose of 600mCi). Partial response was found in 1/6, and tumor progression was assessed in 3/6. Mean follow-up was 6 years.

Conclusion: No association was found regarding age or sex on the development of MPheo. The only clinical difference between MPheo and non-MPheo was the greater tumor size at diagnosis in the former. Due to the absence of clear predictors for malignancy in Pheo, long-term follow-up after surgery is mandatory in these patients.