Outcomes of Oral Vinorelbine in Progressive Desmoid Fibromatosis—Letter
Authors: Chuanxi Zheng, Li Min, Chongqi Tu
Journal: Clinical Cancer Research (2021)

We read with great interest the article by Mir and colleagues that evaluated the efficacy and safety of oral vinorelbine in patients with advanced desmoid fibromatosis (ref. 1). However, we believe that there may yet be some questions left unanswered.A flat dose of vinorelbine lower than the dose routinely used in other solid tumors was chosen to balance the efficacy of drug use against toxic side effects (2). The authors demonstrated that if the tumor-related pain did not remit in the therapeutic period, treatment prolongation until symptomatic improvement was considered. While the authors did not describe the time to best response in each patient, rendering it challenging to evaluate the optimal duration of vinorelbine administration. For the patients who were initially stable on oral vinorelbine but had tumor growth after discontinuation, reinstitution of vinorelbine was again effective to control disease progression, indicating these patients benefited from the prolongated treatment duration. Thus, the appropriate duration of oral vinorelbine for patients with progressive desmoid fibromatosis warrants further elaboration. In addition, the authors did not describe whether the patients with progressive disease under the treatment of a dose of 90 mg would obtain disease stabilization by escalating the dosage to a standard dose of 60–80 mg/m2, although it might be accompanied by more adverse events.Second, the use of RECIST-defined responses to define outcomes among patients with solid tumors remains controversial. Although Mir and colleagues mentioned the potential limitations of RECIST, the interpretation of their results merits further discussion. Assessment of treatment response to systemic therapy for desmoid fibromatosis relying on unidimensional measurement may underestimate patient benefit (3). Because of its unique histologic components, desmoid fibromatosis exhibiting a biologic response to systemic treatment may not shrink (4). Collagenization usually indicates maturation and biological quiescence, presenting a low T2-weighted signal on MRI. In contrast, high T2-weighted signal intensity denotes more aggressive behavior. Thus, the T2-weighted signal intensity can early reflect the biological response of desmoid fibromatosis to systemic therapy. The authors described that the decreased imaging density was observed in several patients who initially achieved stable disease but subsequently experienced partial response during the follow-up. Presumably, these patients had partial response under vinorelbine treatment using the criterion of T2 signal intensity change. More recently, the Choi criteria and revised Choi criteria were shown to be more strongly associated with progression-free survival of patients with desmoid fibromatosis than RECIST 1.1 (5). At the same time, quantitatively analyzing the early change in intralesional heterogeneity through a radiomics score for desmoid fibromatosis under chemotherapy could improve the prediction of dimensional progression (5). However, the use of T2 signal intensity change to assess early response to systemic treatment in desmoid fibromatosis requires further investigation.We commend the authors for their work, and expect that exploration of the issues mentioned above could provide more information to help manage advanced desmoid fibromatosis, and emphasize the necessity for a consistent radiological standard to evaluate the treatment response of desmoid fibromatosis to systemic therapy.No disclosures were reported by the authors.See the Response, p. 2120This work was supported by the National Natural Science Foundation of China (grant nos. 81702664 and 81801852) and the National Key Research and Development Program of China (grant nos. 2016YFC1102003 and 2017YFB0702604).