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Multiple factors help determine when to begin treatment with systemic therapy for patients with radioactive iodine (RAI)-refractory differentiated thyroid cancer (DTC), including the pace of progression, tumor size, and location. Despite the many questions regarding tumor size, it is not the only factor that determines eligibility for systemic therapy, explains Manisha H. Shah, MD.
For patients who present with RAI-refractory DTC, Naifa L. Busaidy, MD, recommends active surveillance for 3 months with CT scan to determine the rate of progression. It is important to determine how rapidly the tumor is progressing before pursuing systemic therapy, particularly for patients with indolent disease. This should be considered along with location and tumor size, Busaidy adds.
Most patients are diagnosed with RAI-refractory DTC by an endocrinologist or a surgeon, who has been seeing the patient for years, states Gary L. Clayman, DMD, MD. For these patients, it is important to begin multidisciplinary care early, even if the medical oncologist does not become the primary physician, notes Marcia S. Brose, MD, PhD. Oncologists can provide a certain level of reassurance for patients through the potentially rapid availability of systemic therapy, should the need arise, Brose adds.
Based on clinical trial data from studies looking at sorafenib and lenvatinib, the median progression-free survival is lower for patients with poor-differentiated histology compared with other histologic subtypes, notes Brose. Patients with this subtype could be candidates for trials looking at combination therapies and aggressive therapy, given the higher risk for progression, notes Brose.
Symptoms should be considered in addition to size, location, and rate of progression, notes Francis P. Worden, MD. Additionally, whether or not to initiate systemic therapy should involve a conversation between the physician and the patient. Moreover, not only does the location of the tumor play a role in the occurrence of symptoms, it also helps predict response. In general, patients with primarily pulmonary disease are more likely to respond to systemic therapy than patients with brain metastases, notes Worden.