The management of pheochromocytomas and paragangliomas (PPGLs) has long been one of the most complex challenges in clinical endocrinology and oncology. These rare neuroendocrine tumors, which arise from the adrenal medulla or the extra-adrenal sympathetic and parasympathetic paraganglia, possess a clinical unpredictability that often leaves physicians with more questions than answers. Because there are currently no definitive biochemical, histological, or imaging markers that can reliably distinguish a benign tumor from a malignant one, clinical guidelines have traditionally dictated that all PPGLs be treated as having metastatic potential. This cautious approach remains the standard even though approximately 75% of these tumors remain localized throughout a patient’s life.
To address this diagnostic and therapeutic gap, a team of researchers led by Camilo Jimenez, MD, from the Department of Endocrine Neoplasia and Hormonal Disorders at the University of Texas MD Anderson Cancer Center, has developed a pioneering treatment algorithm. Published in the Journal of Clinical Endocrinology & Metabolism (JCEM), the paper "Approach to the patient with metastatic pheochromocytoma and paraganglioma: advances in systemic therapy" introduces a framework designed to bring precision medicine to a field historically reliant on broad-spectrum, toxic interventions. The algorithm integrates tumor genotype and clinical phenotype to guide clinicians through a rapidly expanding landscape of systemic therapies, including radioligands, tyrosine-kinase inhibitors, and targeted molecular agents.
The Limitations of Traditional Staging and Therapy
For decades, the primary tool for assessing cancer progression has been the TNM (Tumor, Node, Metastasis) staging system. In the context of PPGLs, the TNM system relies on the size of the primary tumor and its anatomical location to predict the likelihood of spread. However, experts have increasingly recognized that this system is incomplete for neuroendocrine tumors. PPGLs are highly heterogeneous; a small tumor may behave aggressively while a large one remains indolent for years.
Until recently, the mainstay for treating metastatic or unresectable PPGLs was the "CVD" chemotherapy regimen—a combination of cyclophosphamide, vincristine, and dacarbazine. While CVD can be effective in shrinking tumors and controlling symptoms caused by catecholamine excess (such as severe hypertension and palpitations), it is associated with significant systemic toxicity. The emergence of newer therapies has provided alternatives, but the sheer variety of these options—ranging from the radiopharmaceutical Lutetium-177-DOTATATE to the oral medication belzutifan—has created a "paradox of choice" for clinicians. Without a structured way to match a specific patient to a specific drug, the risk of suboptimal treatment remains high.
A Molecular Roadmap: The Four-Cluster Algorithm
The cornerstone of the research by Dr. Jimenez and his colleagues is a classification system that moves beyond anatomy and into the molecular heart of the tumor. The algorithm categorizes patients into four distinct groups based on their molecular profile. These profiles are largely determined by the genetic mutations driving the tumor, such as mutations in the succinate dehydrogenase (SDHx) genes, the von Hippel-Lindau (VHL) gene, or the RET proto-oncogene.
Once a patient is assigned to a molecular group, the algorithm further subclassifies them based on the rate of disease progression. This is a critical distinction, as some metastatic PPGLs are slow-growing (indolent) and may only require monitoring or mild intervention, while others are rapidly progressive and necessitate immediate, aggressive systemic therapy. By combining genotype (what the tumor is) with phenotype (how the tumor behaves), the MD Anderson team provides a roadmap for selecting first-line and second-line treatments, as well as identifying candidates for ongoing clinical trials.
Clinical Application: A Case of Evolution and Adaptation
The practical utility of this algorithm is best illustrated by a case study detailed in the JCEM paper. In 2020, a 67-year-old male presented with a constellation of symptoms including progressive fatigue, abdominal pain, hypertension, and headaches. Diagnostic testing revealed a large, highly vascular primary tumor. Genetic screening identified a mutation consistent with paraganglioma syndrome type 4 (SDHD mutation).
Because the tumor’s location made it unresectable at the time of presentation, the medical team opted for CVD chemotherapy. The goal was cytoreduction—shrinking the tumor enough to allow for a safer surgical intervention. The strategy was initially successful; following chemotherapy and subsequent resection, the patient remained disease-free for two years. However, when the tumor eventually recurred, its behavior had changed.
The recurrence was no longer classified as "rapidly progressing," though it was deemed incurable. Under the new algorithm, the medical team shifted away from the toxic CVD regimen. They instead initiated radiopharmaceutical therapy with Lutetium-177-DOTATATE, a targeted treatment that delivers radiation directly to cells expressing somatostatin receptors. While this therapy required intensive care unit (ICU) monitoring during administration, it represented a more targeted approach than traditional chemotherapy.
The patient’s journey eventually led to the use of belzutifan, a selective small-molecule inhibitor of hypoxia-inducible factor 2α (HIF2α). Belzutifan, which received U.S. Food and Drug Administration (FDA) approval for certain PPGL-related conditions in 2025, offered a convenient oral alternative that resulted in sustained symptomatic improvement. This case underscores a central tenet of the MD Anderson algorithm: treatment must evolve alongside the tumor.
Belzutifan and the Shift Toward Targeted Inhibitors
The inclusion of belzutifan in the treatment algorithm marks a significant milestone in the history of PPGL therapy. The drug is the result of 25 years of scientific research into the pseudohypoxia pathway. In patients with certain genetic mutations, the body’s cells behave as if they are deprived of oxygen, even when oxygen levels are normal. This "pseudohypoxia" triggers the overproduction of HIF2α, which in turn drives tumor growth and the formation of new blood vessels (angiogenesis).
Dr. Jimenez notes that while belzutifan is a "lovely medication" that provides a much-needed option for patients with pseudohypoxic tumors, it is not a universal cure. "It doesn’t work for everyone, and it doesn’t cure the disease," Jimenez stated during a presentation at the ENDO 2025 conference. "But it works for some patients for some time. It’s the beginning of finding better answers."
The drug’s approval and its placement as a potential first-line option for specific molecular subtypes signify the transition of PPGL treatment from "one-size-fits-all" chemotherapy to a more nuanced, pathway-focused oncology.
Global Implications and the Democratization of Care
One of the most significant aspects of the MD Anderson algorithm is its intended global reach. Dr. Jimenez, who serves on the European Society for Medical Oncology (ESMO) guideline panel, designed the framework to be adaptable to different healthcare environments. He acknowledges that while the United States has access to the latest FDA-approved drugs and advanced genetic sequencing, many regions do not.
"The algorithm is designed with everybody around the world in mind," Jimenez explained. In lower-resource settings, the algorithm encourages clinicians to focus on the rate of disease progression and the most effective obtainable therapy. If genetic testing or belzutifan is unavailable, the algorithm still provides a logical framework for using more accessible treatments, such as chemotherapy, but with a more sophisticated understanding of when and why those choices are being made.
The challenge of "democratizing" this level of care is substantial. Molecular subtyping requires specialized laboratory equipment and expertise that remain prohibitively expensive in many countries. Furthermore, even when a drug like belzutifan is approved by multiple regulatory agencies, its cost and distribution can limit its availability to the general population.
The Future of Orphan Disease Research
As a designated "orphan disease," PPGL presents unique hurdles for clinical research. The small number of patients makes it nearly impossible for a single institution—or even a single country—to recruit a large enough population for a traditional Phase 3 clinical trial. Such trials are the gold standard for proving the efficacy of new drugs, but they require massive funding and international cooperation.
Dr. Jimenez remains realistic about these limitations. He emphasizes that the current data in the field, while promising, often comes from smaller cohorts. This makes the need for rigorous, high-quality data even more pressing. The algorithm is intended to be a living document, one that will be updated as international collaborations yield more robust evidence.
The shift toward molecular-based treatment for PPGLs mirrors broader trends in oncology, where the "organ of origin" is becoming less important than the "mutation of origin." By focusing on the underlying biology of the tumor, the MD Anderson team is helping to transition PPGL management into the era of personalized medicine.
For patients, this shift offers the hope of not only longer survival but also a better quality of life. By avoiding the broad-spectrum toxicity of older treatments when more targeted options are available, clinicians can tailor interventions to the individual needs of the patient. As Dr. Jimenez concludes, while the underlying biology of these tumors remains the same across the globe, the individual situations of patients are vastly different, and their treatment plans should reflect that reality.
