Transition of treatment for patients with extra-abdominal desmoid tumors: nagoya university modality

A Desmoid Tumor Responding to Systemic Therapy With Tamoxifen and Sulindac

Desmoid tumors are locally aggressive benign tumors arising from connective tissue and are classified as soft tissue sarcomas that do not metastasize. The name is derived from the Greek word desmos that means tendon-like. These tumors are also known as aggressive fibromatosis and have an unpredictable natural history that varies depending on risk factors. They are treated as sarcomas because of their locally aggressive nature and a high local recurrence rate. The causes behind desmoid tumor development are enigmatic and their clinical course is unpredictable. Disease progression also varies widely depending on multiple syndromic risk factors. At this time, there is no scientific consensus over best treatment practices for this tumor type. Treatment can potentially be a combination of observation, systemic therapy, surgery or radiation therapy. Here, we have described a case of a female patient with a sporadic desmoid tumor that successfully responded to tamoxifen and sulindac.

Clinical results of active surveillance for extra-abdominal desmoid-type fibromatosis

BACKGROUND

The treatment of choice for desmoid-type fibromatosis (DF) has been changed to active surveillance (AS). However, few studies have reported clinical outcomes of AS modality in Asian countries. This study aimed to clarify the significance of AS as a DF treatment modality.

METHODS

A total of 168 lesions from 162 patients with extra-abdominal DF were included. The mean age at diagnosis was 39 years (1-88 years), and the median maximum tumor diameter at the first visit was 64.1 mm (13.2-255.8 mm). The clinical outcomes of AS and the risk factors requiring active treatment (AT) (defined as an event) from AS modality were investigated.

RESULTS

Of the 168 lesions, 94 (56%) were able to continue AS, with a 5-year event-free survival of 54.8%. Of the 68 lesions with PD, 21 (30.9%) lesions were able to continue AS. Neck location (p = 0.043) and CTNNB1 S45F mutation (p = 0.003) were significantly associated with the transition to AT, and S45F mutation was a significant factor associated with the transition to AT by multivariate analysis (hazard ratio: 1.96, p = 0.048). AT outcomes after AS were evaluable in 65 lesions, and 49 (75%) lesions did not require a transition to a second AT.

CONCLUSIONS

AS was revealed as an effective treatment modality. The transition to AT needs to be considered for neck location and CTNNB1 S45F mutation DF. Good results can be obtained by selecting a treatment method that considers the tumor location even in cases that require intervention.

Efficacy of auranofin as an inhibitor of desmoid progression

Anticancer drugs and molecular targeted therapies are used for refractory desmoid-type fibromatosis (DF), but occasionally cause severe side effects. The purpose of this study was to identify an effective drug with fewer side effects against DF by drug repositioning, and evaluate its efficacy. FDA-approved drugs that inhibit the proliferation of DF cells harboring S45F mutations of CTNNB1 were screened. An identified drug was subjected to the investigation of apoptotic effects on DF cells with analysis of Caspase 3/7 activity. Expression of β-catenin was evaluated with western blot analysis, and immunofluorescence staining. Effects of the identified drug on in vivo DF were analyzed using Apc1638N mice. Auranofin was identified as a drug that effectively inhibits the proliferation of DF cells. Auranofin did not affect Caspase 3/7 activity compared to control. The expression level of β-catenin protein was not changed regardless of auranofin concentration. Auranofin effectively inhibited the development of tumorous tissues by both oral and intraperitoneal administration, particularly in male mice. Auranofin, an anti-rheumatic drug, was identified to have repositioning effects on DF. Since auranofin has been used for many years as an FDA-approved drug, it could be a promising drug with fewer side effects for DF.

Breast Sarcomas, Phyllodes Tumors, and Desmoid Tumors: Epidemiology, Diagnosis, Staging, and Histology-Specific Management Considerations

Breast sarcomas arise from connective tissues of the breast and account for fewer than 1% of all breast malignancies. They can be subclassified as primary breast sarcomas, which arise de novo and are histologically diverse, and secondary breast sarcomas, which arise as a result of radiation or lymphedema and are most commonly angiosarcomas. Two other connective tissue neoplasms that occur within the breast include phyllodes tumors and desmoid tumors, which exhibit a spectrum of behaviors. Malignant phyllodes tumors are biologically similar to primary breast sarcomas, whereas desmoid tumors are technically benign but often locally aggressive. Patients with breast sarcomas often present with a rapidly growing mass or, in cases of radiation-associated angiosarcoma, violaceous cutaneous lesions. Core needle biopsy is generally required to confirm the diagnosis of sarcomas. Staging workup includes MRI and chest imaging, although these are not required in the case of benign phyllodes or desmoid tumors. In general, localized breast sarcomas should be resected, with the extent of resection tailored to histologic subtype. Radiation and chemotherapy can be used in the neoadjuvant or adjuvant setting, but data are limited, so treatment decisions should be made on an individualized basis. Systemic therapy options for metastatic disease and refractory breast desmoids mimic those used for the same histologies when present in other sites. Given the rarity and heterogeneity of breast sarcoma, as well as limited literature describing these entities, expert multidisciplinary evaluation is crucial for optimal decision making.

Management of aggressive fibromatosis

Aggressive fibromatosis or desmoid tumor is a rare disease resulting from fibroblasts which do not metastasize. However, desmoid tumors belong to low-grade malignant tumors since they have high potential to infiltrate surrounding tissues, causing high local recurrence rates and may affect surrounding organs, threatening life quality and expectancy. Although surgery, watch and wait, radiotherapy, chemotherapy, high intensity focused ultrasound, ablation techniques or several agents have all been frequently investigated for the treatment of this type of disease, none are deemed as standard therapy for high recurrence rates that have been supported by any data. The present review retrieved literature on treatment options for desmoids to summarize the latest treatment modalities and refine their efficacy, as well as their side effects, in order to provide a more comprehensive treatment reference for clinicians.

Is mutation analysis of β-catenin useful for the diagnosis of desmoid-type fibromatosis? A systematic review

BACKGROUND

An accurate diagnosis is crucial to determine the treatment modality for desmoid-type fibromatosis, although the histopathological diagnosis is occasionally difficult to make. Many desmoid-type fibromatosis have been reported to have hotspot mutation of β-catenin gene (CTNNB1). In the present study, we performed a systematic review to verify the usefulness of CTNNB1 mutation analysis in the diagnosis of desmoid-type fibromatosis.

METHODS

A literature search from January 1990 to August 2017 was conducted. Three reviewers independently assessed and screened the literature for eligibility and determined the final articles to be evaluated. Data regarding the sensitivity, specificity, accuracy and usefulness of CTNNB1 mutation analysis in the diagnosis of desmoid-type fibromatosis were recorded. We rated each report according to the Grading of Recommendations Development and Evaluation approach.

RESULTS

The search yielded 90 studies, seven of which were included after the first and second screenings. The positive rate of CTNNB1 mutation in desmoid-type fibromatosis was 86.8%, but the cohort of six of the seven reports was already diagnosed histopathologically as desmoid-type fibromatosis. Therefore, the usefulness of CTNNB1 mutation analysis in a cohort that is difficult to diagnose histopathologically is not clear in this review. Nevertheless, CTNNB1 mutation showed very high specificity in desmoid-type fibromatosis, indicating the usefulness of CTNNB1 mutation analysis in its diagnosis in combination with histological examination.

CONCLUSION

Because the lack of data precludes any useful comparison with histological diagnosis, the evidence level is low. However, considering its specificity, CTNNB1 mutation analysis may be useful in cases in which the histopathological diagnosis is difficult.

Desmoid with biweekly methotrexate and vinblastine shows similar effects to weekly administration: A phase II clinical trial

Low-dose methotrexate (MTX) plus vinblastine (VBL) chemotherapy is an effective treatment for desmoid-type fibromatosis (DF). However, previous reports have described a weekly regimen, with no reports available on a biweekly one. The aim of this study was to determine the clinical outcomes of a biweekly regimen in a cohort prospectively treated in our single institution. Since 2010, we have prospectively treated refractory DF patients with biweekly MTX (30 mg/m² ) + VBL (6 mg/m² ). Efficacy, progression-free survival (PFS), and correlating factors were analyzed. Adverse events (AEs) were recorded. In total, 38 patients received low-dose MTX + VBL therapy, and its efficacy was assessed in 37 of them. Nineteen (51%) patients showed partial response (PR). Clinical benefit rate was 95%. PFS at 5 y was 80.8%. In PR cases, median time to response was 10 mo. Longer duration of therapy was significantly associated with the response of PR (P = .007) by univariate analysis. There was no clear association between various clinicopathological factors, including tumor size, location, catenin beta-1 (CTNNB1) mutation status with effect. Only 3 AEs of grade 3/4 were observed. Tumor regrowth after MTX + VBL discontinuation was observed in 5 (20%) of 25 patients. Biweekly administration of MTX + VBL chemotherapy was well tolerated compared with weekly administration, and its efficacy was anticipated in DF patents, although the time needed to achieve a response may be relatively long. The treatment interval should be determined taking into account both the condition of the tumor and the patient's preference.

MRI characteristics predict the efficacy of meloxicam treatment in patients with desmoid-type fibromatosis

INTRODUCTION

This study aimed to determine the clinical significance of MRI characteristics as a possible predictor of responsiveness to meloxicam treatment in patients with desmoid-type fibromatosis (DF). Additionally, it analysed the correlation between CTNNB1 mutation status and signal intensity of MRI.

METHODS

Forty-six patients consecutively treated with meloxicam composed this study. The low-intensity area (LIA) on T2-weighted MRI was determined. We divided patients into two groups based on the efficacy of meloxicam: a clinical benefit group (CB group, including CR: complete response; PR: partial response; and SD: stable disease) and non-clinical benefit group (NB group, including PD: progressive disease). Correlations of the efficacy with LIA and CTNNB1 mutation status with LIA were investigated.

RESULTS

In total, 11, 17 and 18 patients showed PR, SD and PD, respectively. The mean LIA ratio before treatment was significantly higher (P < 0.001) in the CB group than in the NB group. For predicting the efficacy, sensitivity was 68%, and specificity was 89% when setting the cut-off value as 20% for LIA. Mean changes in the LIA ratio before and after treatment were significantly higher (P = 0.01) in the CB group than in the NB group. Mean LIA ratio before treatment was significantly lower (P < 0.001) in the S45F mutation group than in the other mutation group. In multivariate analysis, the LIA ratio before treatment was a significant predictor of responsiveness (P = 0.02).

CONCLUSIONS

MRI characteristics were a useful predictor of the efficacy of meloxicam in DF patients. It may be possible to predict the clinical outcome more accurately when combined with other factors, such as CTNNB1 mutantion status.

Clinical features and treatment outcome of desmoid-type fibromatosis: based on a bone and soft tissue tumor registry in Japan

BACKGROUND

Treatment modality of desmoid-type fibromatosis (DF) has changed from surgery with a wide surgical margin to conservative treatment. In this study, tumor characteristics of DF, transition of the treatment modality, and clinical outcome of surgical treatment were analyzed based on data obtained from the bone and soft tissue tumor registry established in Japan.

METHODS

Data were collected as registration data and follow-up data. Five hundred and thirty registered cases of DF were identified, including 223 cases with follow-up data with or without surgical treatment.

RESULTS

The number of registered patients increased gradually. The frequency of surgical treatment was gradually reduced year by year. The 3-year local recurrence free survival (LRFS) was 77.7%, with tumor location and size tending to correlate with LRFS. Interestingly, there was no significant difference in LRFS between wide and marginal margin (P = 0.34).

CONCLUSIONS

The treatment modality has shifted from surgical to conservative treatment, with risk factors for surgical treatment similar to those noted in previous studies. The National registry system is crucial for a rare disease such as DF, and in the future, a population based registry system should be established to better comprehend the actual status of DF.

Magnetic Resonance Imaging-guided High-intensity Focused Ultrasound Applications in Pediatrics: Early Experience at Children's National Medical Center

Magnetic resonance imaging-guided high-intensity focused ultrasound (MR-HIFU) is a novel technology that integrates magnetic resonance imaging with therapeutic ultrasound. This unique approach provides a completely noninvasive method for precise thermal ablation of targeted tissues with real-time imaging feedback. Over the past 2 decades, MR-HIFU has shown clinical success in several adult applications ranging from treatment of painful bone metastases to uterine fibroids to prostate cancer and essential tremor. Although clinical experience in pediatrics is relatively small, the advantages of a completely noninvasive and radiation-free therapy are especially attractive to growing children. Unlike elderly patients, young children must deal with an entire lifetime of negative effects related to collateral tissue damage associated with invasive surgery, side effects of chemotherapy, and risk of secondary malignancy due to radiation exposure. These reasons provide a clear rationale and strong motivation to further advance clinical utility of MR-HIFU in pediatrics. We begin with an introduction to MR-HIFU technology and the clinical experience in adults. We then describe our early institutional experience in using MR-HIFU ablation to treat symptomatic benign, locally aggressive, and metastatic tumors in children and young adults. We also review some limitations and challenges encountered in treating pediatric patients and highlight additional pediatric applications which may be feasible in the near future.

Systematic Review of Clinical Outcomes Following Various Treatment Options for Patients with Extraabdominal Desmoid Tumors

BACKGROUND

Desmoid tumors (DT) are rare clonal proliferations that arise from mesenchymal cells. These tumors do not metastasize but are locally aggressive, and their growth may lead to significant morbidity. Their clinical course is both variable and unpredictable; tumors may rapidly progress but in other instances remain stable or regress without intervention.

AIMS

To examine current treatment of DT and assist with decision-making at time of presentation.

METHODS

A literature search was conducted of MEDLINE and Cochrane databases for published studies (1995-July 2015) using the search terms fibromatosis aggressive, desmoid with drug therapy, radiation therapy, prevention and control, radiotherapy, surgery, and therapy. Articles were categorized as surgery, radiation, surgery + radiation, systemic therapy, and front-line observation. Articles were included if they reported a retrospective or prospective comparative or observational study with an analyzed sample size of 10 patients or more with confirmed diagnosis of desmoid tumor and described one of the following clinical outcomes: relapse- or progression-free survival, local control rate, response rate.

RESULTS

258 articles were reviewed; following screening for eligibility, 54 were identified; following full-text screen, 31 were included in final evaluation. The control rate for patients treated with a "wait and see" observational approach compared favorably with management with surgery and resulted in disease control rates of between 60 and 92%.

CONCLUSIONS

Decision-making in this rare tumor is complicated by the range of treatment options available. Our evidence supports use of an upfront observational approach.

Immunohistochemical staining with non-phospho β-catenin as a diagnostic and prognostic tool of COX-2 inhibitor therapy for patients with extra-peritoneal desmoid-type fibromatosis

Background

Immunohistochemical staining with conventional anti-β-catenin antibody has been applied as a diagnostic tool for desmoid-type fibromatosis (DF). This study aimed to evaluate the diagnostic and prognostic value of immunohistochemical staining with anti-non-phospho β-catenin antibody, which might more accurately reflect the aggressiveness of DF, in comparison to the conventional anti-β-catenin antibody.

Methods

Between 2003 and 2015, 40 patients with extra-peritoneal sporadic DF were prospectively treated with meloxicam or celecoxib, a COX-2 inhibitor, therapy. The efficacy of this treatment was evaluated according to Response Evaluation Criteria in Solid Tumors (RECIST). Immunohistochemical staining was performed on formalin-fixed material to evaluate the expression of β-catenin and non-phospho β-catenin, and the positivity was grouped as negative, weak, moderate, and strong. DNA was isolated from frozen tissue or formalin-fixed materials, and the CTNNB1 mutation status was determined by direct sequencing.

Results

Of the 40 patients receiving COX-2 inhibitor treatment, there was one with complete remission, 12 with partial remission, 7 with stable disease, and 20 with progressive disease. The mutation sites in CTNNB1 were detected in 22 (55%) of the 40 cases: T41A (17 cases), S45F (3 cases), and T41I and S45P (1 each). The positive nuclear expression of non-phospho β-catenin showed a significant correlation with positive CTNNB1 mutation status detected by Sanger method (p = 0.025), and poor outcome in COX-2 inhibitor therapy (p = 0.022). In contrast, nuclear expression of β-catenin did not show a significant correlation with either CTNNB1 mutation status (p = 0.43) or outcome of COX-2 inhibitor therapy (p = 0.38).

Conclusions

Nuclear expression of non-phospho β-catenin might more appropriately reflect the biological behavior of DF, and immunohistochemical staining with non-phospho β-catenin could serve as a more useful diagnostic and prognostic tool of COX-2 inhibitor therapy for patients with DF.

Simple resection of truncal desmoid tumors: A case series

Desmoid tumors of the extra-abdominal and abdominal wall have been associated with morbidity due to the aggressive nature of the surgery and high recurrence rates. Surgery that does not cause functional impairment is desired for patients with desmoid tumors. In the present study, among patients with desmoid tumors who were prospectively and consecutively treated with identical conservative treatment with meloxicam, a selected patients of patients were treated with less invasive surgery than wide-resection. Out of 60 patients pathologically diagnosed with desmoid tumors, 9 patients with tumors refractory to conservative treatment and 4 patients who refused to receive this type of treatment were treated with planned simple resection. Subsequently, the clinical outcome of the patients and the mutational status of the catenin β-1 (CTNNB1) gene in the tumors were analyzed. The mean age of the 13 patients that underwent planned simple resection was 39 years, and the tumors were located in the abdominal wall in 6 cases, the chest wall in 4 cases and the neck in 3 cases. All excised specimens were evaluated and positive microscopic margins were identified; however, during the mean follow-up period of 30 months, 12/13 cases, 7 of which had T41A mutations and 5 of which had no mutations (wild-type), did not develop recurrence. Only 1 initial case with an S45F mutation in the CTNNB1 gene developed recurrence. The results of the present prospectively treated with simple resection and retrospectively analyzed study suggest that planned simple resection could serve as a therapeutic modality for extraperitoneal desmoid tumors, particularly truncal ones with a wild-type or T41A mutational status.

Primary and recurrent sporadic desmoids: Prognostic factors influencing recurrence-free survival after complete gross resection

INTRODUCTION

There is continuing controversy over the significance of prognostic factors in sporadic desmoid-type fibromatosis (DF). Further, only limited data is available in the literature concerning second recurrence in patients with recurrent DF. The purpose of this study was to identify prognostic factors influencing recurrence-free survival (RFS) and to determine rates of local recurrence (LR) in patients with primary and recurrent DF.

METHODS

Fifty-three consecutive patients with DF who underwent surgery at a single institution were identified. As a result of strict exclusion criteria, a homogeneous cohort of thirty-two patients who received macroscopically complete resection was included in this study and split into a primary (PG) and recurrent disease (RG) group. Clinicopathological parameters and immunohistochemical markers were retrospectively and independently analyzed in both groups.

RESULTS

The local recurrence rate was 35% for the PG and 33% for the RG. The PG's calculated median time to relapse was 17 months, and the RG's was 29 months. The estimated 1-, 5-, and 8-year RFS rates for the PG were 75%, 64%, and 55% while the corresponding RFS rates for the RG were 69%, 69%, and 52%, respectively. In primary disease, extraabdominal tumor location was the only significant adverse prognostic factor associated with worse RFS (p = 0.008). Whereas in recurrent disease, age ≥40 yrs (p = 0.022) and R0 margin status (p = 0.049) correlated with a significantly better outcome.

CONCLUSION

Recurrence in primary and recurrent DF is characterized by different predictive factors and benefits from distinct therapeutic strategies. Immunohistochemical markers are valuable tools in the diagnosis of DF, although have limited potential in predicting the outcome.

Characteristics of cultured desmoid cells with different CTNNB1 mutation status

Desmoid tumors are benign mesenchymal neoplasms with a locally aggressive nature. The mutational status of β‐catenin gene (CTNNB1) is presumed to affect the tumorous activity of the cells. In this study, we isolated three kinds of desmoid cell with different CTNNB1 status, and compared their characteristics. Cells were isolated from three patients with abdominal wall desmoid during surgery, all of which were resistant to meloxicam treatment. The mutational status of the CTNNB1 exon 3 was determined for both parental tumor tissues and isolated cultured cells. β‐catenin expression was determined with immunohistochemistry. Responsiveness to meloxicam was investigated with MTS assay together with COX‐2 immunostaining. mRNA expressions of downstream molecules of Wnt/β‐catenin pathway were determined with real‐time RT‐PCR. Three kinds of cell isolated from desmoid tumors harboring different CTNNB1 mutation status (wild type, T41A, and S45F), all exhibited a spindle shape. These isolated cells could be cultured until the 20th passage with unchanged proliferative activity. Nuclear accumulation of β‐catenin was observed in all cultured cells, particularly in those with S45F. Proliferating activity was significantly suppressed by meloxicam (25 μmol/L, P < 0.007) in all three cell cultures, of which parental desmoid was resistant to meloxicam clinically. The mRNA expressions of Axin2, c‐Myc, and Cyclin D1 differently increased in the three cultured cell types as compared with those in human skin fibroblast cells (HDF). Inhibitors of Wnt/β‐catenin pathway downregulated Axin2, c‐Myc, and Cyclin D1 significantly. Isolated and cultured desmoid tumor cells harboring any one of the CTNNB1 mutation status had unique characteristics, and could be useful to investigate desmoid tumors with different mutation status of CTNNB1.

Treatment and follow-up strategies in desmoid tumours: a practice guideline

OBJECTIVES

We set out to determine the optimal treatment options-surgery, radiation therapy (rt), systemic therapy, or any combinations thereof-for patients with desmoid tumours once the decision to undergo active treatment has been made (that is, monitoring and observation have been determined to be inadequate).provide clinical-expert consensus opinions on follow-up strategies in patients with desmoid tumours after primary interventional management.

METHODS

This guideline was developed by Cancer Care Ontario's Program in Evidence-Based Care and the Sarcoma Disease Site Group. The medline, embase, and Cochrane Library databases, main guideline Web sites, and abstracts of relevant annual meetings (1990 to September 2012) were searched. Internal and external reviews were conducted, with final approval by the Program in Evidence-Based Care and the Sarcoma Disease Site Group.

RECOMMENDATIONS TREATMENTS

Surgery with or without rt can be a reasonable treatment option for patients with desmoid tumours whose surgical morbidity is deemed to be low.The decision about whether rt should be offered in conjunction with surgery should be made by clinicians and patients after weighing the potential benefit of improved local control against the potential harms and toxicity associated with rt.Depending on individual patient preferences, systemic therapy alone or rt alone might also be reasonable treatment options, regardless of whether the desmoid umours are deemed to be resectable.

RECOMMENDATIONS FOLLOW-UP STRATEGIES

Undergo evaluation for rehabilitation (occupational therapy or physical therapy, or both).Continue with rehabilitation until maximal function is achieved.Undergo history and physical examinations with appropriate imaging every 3-6 months for 2-3 years, and then annually.

A systematic review of active treatment options in patients with desmoid tumours

INTRODUCTION

We conducted a systematic review to determine the optimal treatment options in patients with desmoid tumours who have declined observational management.

METHODS

A search was conducted of the medline and embase databases (1990 to September 2012), the Cochrane Library, and relevant guideline Web sites and conference materials.

RESULTS

One systematic review and forty-six studies met the preplanned study selection criteria; data from twenty-eight articles were extracted and analyzed. For local control, three studies reported a statistically significant difference in favour of surgery plus radiotherapy (rt) compared with surgery alone, and one study did not; two studies reported the lack of a statistical difference between surgery plus rt and rt alone in maintaining local control. Multivariate risk factors for local recurrence included positive surgical margins and young patient age. Single-agent imatinib led to a progression-free survival rate of 55% at 2 years and 58% at 3 years. Methotrexate plus vinblastine led to a progression-free survival rate of 67% at 10 years. Significant toxicities were reported for all treatment modalities, including surgical morbidity, and rt- and chemotherapy-related toxicities.

CONCLUSIONS

In patients who have declined observational management, the local control rate was higher with surgery plus rt than with surgery alone. However, the additional rt-related complications should be considered in treatment decision-making. Surgery, rt, and systemic therapy are all reasonable treatment options for patients with desmoid tumours.

CTNNB1 S45F mutation predicts poor efficacy of meloxicam treatment for desmoid tumors: a pilot study

We hypothesized that patterns of CTNNB1 (β-catenin) mutations would affect the outcome of conservative therapy in patients with desmoid tumors. This study aimed to determine the significance of CTNNB1 (β-catenin) mutations in predicting the treatment outcome in patients with desmoid tumors treated with meloxicam, a cyclooxygenase-2 (COX-2) selective inhibitor. Between 2003 and 2012, consecutive thirty-three patients with extra-peritoneal sporadic desmoid tumors were prospectively treated with meloxicam as the initial systemic medical therapy. The efficacy of meloxicam was evaluated according to Response Evaluation Criteria in Solid Tumors (RECIST). DNA was isolated from frozen tissue or formalin-fixed materials. CTNNB1 mutation analysis was performed by direct sequencing. Positivity of nuclear β-catenin staining by immunohistochemistry was compared with the status of CTNNB1 mutations. The correlation between the efficacy of meloxicam treatment and status of CTNNB1 mutations was analyzed. Of the 33 patients with meloxicam treatment, one showed complete remission (CR), 7 partial remission (PR), 12 stable disease (SD), and 13 progressive disease (PD). The following 3 point mutations were identified in 21 of the 33 cases (64%): T41A (16 cases), S45F (4 cases) and S45P (one case). The nuclear expression of β-catenin correlated significantly with CTNNB1 mutation status (p = 0.035); all four cases with S45F mutation exhibited strong nuclear expression of β-catenin. S45F mutation was significantly associated with a poor response (all cases; PD) (p = 0.017), whereas the other mutations had no impact on efficacy. The CTNNB1 mutation status was of significant prognostic value for meloxicam treatment in patients with sporadic desmoid tumors.