Prognostic factors for refractory pheochromocytoma and paraganglioma after ¹³¹I-metaiodobenzylguanidine therapy

Objective

Given the rarity of refractory pheochromocytoma and paraganglioma (PPGL), outcomes and prognostic factors after ¹³¹I-metaiodobenzylguanidine (¹³¹I-mIBG) treatment still remain unclear. Therefore, this study evaluated whether baseline characteristics at initial ¹³¹I-mIBG therapy and imaging response to repeated ¹³¹I-mIBG therapy could be prognostic factors for refractory PPGL.

Methods

All patients [n = 59 (male/female = 35/24), median age; 49.3 years] with refractory PPGL who received ¹³¹I-mIBG therapy at our institution between September 2009 and September 2019 were retrospectively reviewed for the effects of the following factors on overall survival: age, sex, hypertension, diabetes mellitus, palpitations, constipation, cancer pain, catecholamines values, past history of therapy (external beam radiation for bone metastasis, operation, and chemotherapy), metastasis sites, and response to ¹³¹I-mIBG treatments.

Results

Throughout the follow-up period, 18 patients died from disease exacerbation. The estimated 5- and 10-year survival rates were 79.4% and 67.2% from the initial diagnoses of refractory PPGL and 68.5% and 49.9% from the first ¹³¹I-mIBG therapy, respectively. The multivariate Cox proportional hazards model showed that progressive disease (PD) [hazard ratio (HR) 96.3, P = 0.011] and constipation (HR 8.2, P = 0.024) were adverse prognostic factors for overall survival after initial ¹³¹I-mIBG therapy. The log-rank test demonstrated that PD in response to ¹³¹I-mIBG therapies (P < 0.0001) and constipation (P < 0.01) were correlated with poor survival rates.

Conclusions

Response to repeated ¹³¹I-mIBG treatment can be a strong predictor of prognosis after initial ¹³¹I-mIBG therapy for refractory PPGL. Repeated ¹³¹I-mIBG therapy may be a good option for controlling refractory PPGL. (author)