Standard RECIST criteria can misclassify a significant response as "stable disease." A desmoid tumor can shrink dramatically in volume (from a "softball" to a "pencil") but maintain its length, showing no change by RECIST. This suggests clinicians are likely underestimating the true benefit of therapies.

As more effective treatments for desmoid tumors become available, a critical unmet need is emerging: knowing when to stop therapy. Future research must focus on identifying signals, such as radiologic changes on MRI, to guide treatment duration. This will help clinicians avoid both the risk of early relapse from stopping too soon and the toxicity of unnecessary overtreatment.

Desmoid tumors exhibit highly variable behavior, acting as a chronic disease in some patients while being manageable in others. This necessitates a personalized, long-term treatment strategy rather than a standard protocol, often requiring a diverse armamentarium of therapeutic options to be used over a patient's lifetime as needs change.

While new systemic treatments for desmoid tumors can effectively control the disease and improve quality of life by managing symptoms, they introduce their own set of side effects. This creates a clinical challenge where the positive impact on the tumor must be carefully weighed against the negative impact of the treatment itself on the patient's daily life.

Desmoid tumors can shrink without treatment, a phenomenon seen in up to 35% of patients under observation. This inherent biological behavior makes it difficult to prove that continued tumor reduction during long-term therapy is solely due to the drug's effect.

The standard of care for desmoid tumors has shifted away from upfront surgery due to high recurrence rates and poor patient outcomes. Experts now recommend systemic or other local therapies first, reserving surgery only for emergencies or after careful multidisciplinary team review.

Following cryoablation, imaging of a desmoid tumor may show a paradoxical increase in size. This is often a temporary inflammatory response, not disease progression. In one case, initial swelling was followed by symptom improvement and eventual tumor shrinkage, a key finding for interpreting post-procedure scans.

The approval of effective therapies like nirogacestat creates an ethical dilemma. For patients with progressing tumors, continuing to use a placebo arm in clinical trials may no longer be appropriate, challenging future research design for this rare disease.

Patients on niragacestat for desmoid tumors often experience rapid symptom improvement. However, this clinical benefit significantly precedes radiological response (tumor shrinkage on scans), which can take over five months to appear. This disconnect is crucial for managing patient expectations and assessing early treatment efficacy.