The economic burden of gastrointestinal stromal tumor (GIST) recurrence in patients who have received adjuvant imatinib therapy

Event-free survival as a predictor of overall survival and recurrence burden of patients with non-small cell lung cancer receiving neoadjuvant therapy

OBJECTIVES

Event-free survival has replaced overall survival as a primary end point in many recent and ongoing clinical trials. This study aims to examine the correlation between real-world event-free survival and overall survival and to assess the clinical and economic burden associated with disease recurrence among patients with resected stage II to III non-small cell lung cancer who received neoadjuvant therapy in the United States.

METHODS

This retrospective study used the Surveillance, Epidemiology, and End Results Medicare database (2007-2019) to identify patients with newly diagnosed, resected, stage II to IIIB (N2) non-small cell lung cancer who received neoadjuvant therapy. The correlation between real-world event-free survival and overall survival was assessed using the normal scores rank correlation and landmark analysis. Overall survival, all-cause health care resource use and costs, and non-small cell lung cancer-related health care resource use and costs were compared between patients with and without recurrence.

RESULTS

A total of 221 patients met the eligibility criteria (median follow-up time from neoadjuvant treatment initiation: 32.7 months). The mean age was 72.1 years, and 57.0% of patients were male. Real-world, event-free survival and overall survival are positively and significantly correlated (0.68; 95% CI, 0.52-0.79). Patients with recurrence had significantly shorter median overall survival (19.3 vs 116.9 months), 4.59 times increased risk of death (95% CI, 2.56-8.26), and significantly higher all-cause and non-small cell lung cancer-related health care resource use and costs (adjusted mean monthly costs per patient difference: $5758 and $3187, respectively [all P < .001]).

CONCLUSIONS

These findings help validate event-free survival as a clinically meaningful end point and strong predictor for overall survival and highlight the need for additional novel therapies that may delay or prevent recurrence in resectable stage II and III non-small cell lung cancer.

Disease-free survival as a predictor of overall survival in localized renal cell carcinoma following initial nephrectomy: A retrospective analysis of Surveillance, Epidemiology and End Results-Medicare datac

OBJECTIVES

This study aimed to assess whether disease-free survival (DFS) may serve as a predictor for long-term survival among patients with intermediate-high risk or high risk renal cell carcinoma (RCC) post-nephrectomy when overall survival (OS) is unavailable.

METHODS

The Surveillance, Epidemiology and End Results-Medicare database (2007-2016) was used to identify patients with non-metastatic intermediate-high risk and high risk RCC post-nephrectomy. Landmark analysis and Kendall's τ were used to evaluate the correlation between DFS and OS. Multivariable regression models were used to quantify the incremental OS post-nephrectomy associated with increased time to recurrence among patients with recurrence, adjusting for baseline covariates.

RESULTS

A total of 643 patients were analyzed; mean age of 75 years; >95% of patients had intermediate-high risk RCC at diagnosis; 269 patients had recurrence post-nephrectomy. For patients with versus without recurrence at the landmark points of 1, 3, and 5 years post-nephrectomy, the 5-year OS were 37.0% versus 70.1%, 42.3% versus 72.8%, and 53.2% versus 78.6%, respectively. The Kendall's τ between DFS and OS post-nephrectomy was 0.70 (95% CI: 0.65, 0.74; p < 0.001). After adjusting for baseline covariates, patients with one additional year of time to recurrence were associated with 0.73 years longer OS post-nephrectomy (95% CI: 0.40, 1.05; p < 0.001).

CONCLUSION

The significant positive association of DFS and OS among patients with intermediate-high risk and high risk RCC post-nephrectomy from this study supports the use of DFS as a potential predictor of OS for these patients when OS data are immature.

The Application of Virtual Therapeutic Drug Monitoring to Assess the Pharmacokinetics of Imatinib in a Chinese Cancer Population Group

PURPOSE

Imatinib is used in gastrointestinal stromal tumours (GIST) and chronic myeloid leukaemia (CML). Oncology patients demonstrate altered physiology compared to healthy adults, e.g. reduced haematocrit, increased α-1 acid glycoprotein, decreased albumin and reduced glomerular filtration rate (GFR), which may influence imatinib pharmacokinetics. Given that Chinese cancer patients often report raised imatinib plasma concentrations and wider inter-individual variability reported in trough concentration when compared to Caucasian cancer patients, therapeutic drug monitoring (TDM) has been advocated.

METHOD

This study utilised a previously validated a Chinese cancer population and assessed the impact of imatinib virtual-TDM in Chinese and Caucasian cancer populations across a dosing range from 200-800 mg daily.

RESULTS

Staged dose titration to 800 mg daily, resulted in recapitulation to within the target therapeutic range for 50 % (Chinese) and 42.1% (Caucasian) subjects possessing plasma concentration < 550 ng/mL when dosed at 400 mg daily. For subjects with plasma concentrations >1500 ng/mL when dosed at 400 mg daily, a dose reduction to 200 mg once daily was able to recover 67 % (Chinese) and 87.4 % (Caucasian) patients to the target therapeutic range.

CONCLUSION

Virtual TDM highlights the benefit of pharmacokinetic modelling to optimising treatments in challenging oncology population groups.

National Utilization of Imatinib in the Management of Resected Gastrointestinal Stromal Tumors

BACKGROUND

Imatinib decreases recurrence risk and improves overall survival (OS) in localized gastrointestinal stromal tumors (GISTs); however, the extent to which patients receive appropriate treatment in the US has not been well characterized.

METHODS

Patients with non-metastatic, resectable GIST were included in this study (National Cancer Database, 2010-2015). Those with a low-risk of recurrence were classified as receiving overtreatment or guideline-concordant treatment, while those with a high-risk of recurrence were classified as receiving undertreatment or guideline-concordant treatment. Multivariable logistic regression was used to determine factors associated with non-concordant treatment. The association between non-concordant treatment and OS was evaluated using multivariable Cox regression and propensity score matching.

RESULTS

Among 3088 patients with high-risk GIST, 41% were undertreated, and among 3908 patients with low-risk GIST, 18.8% were overtreated. For patients with high-risk GIST, age > 60 years, African American race, and treatment at a community or comprehensive cancer program were associated with undertreatment. Among low-risk patients, small bowel primary, tumor size > 2 cm, and tumors with > 1 mitotic figure per 50 high-power fields were more likely to be overtreated. After propensity score matching, guideline-concordant therapy was associated with an 8.8% improvement in 5-year OS (81.9% vs. 73.1%, p = 0.002) for those with high-risk GIST and decreased risk of death (hazard ratio 0.63, 95% confidence interval 0.47-0.84). There was no statistically significant difference in survival for patients with low-risk GIST with the addition of imatinib overtreatment (overtreatment 93.9% vs. 89.6%, p = 0.053).

CONCLUSIONS

Nearly 30% of GIST patients do not receive guideline-concordant treatment and future work is needed to understand the factors driving non-concordant treatment.

Incidence of gastrointestinal stromal tumor in Chinese urban population: A national population-based study

BACKGROUND

Information on incidence of gastrointestinal stromal tumor (GIST), the most common type of mesenchymal tumor in gastrointestinal tract, was limited in China. This study aimed to estimate the incidence of GIST in urban population from mainland China in 2016.

METHODS

Urban Employee Basic Medical Insurance (UEBMI) and Urban Residence Basic Medical Insurance (URBMI) in China were used. The denominator of incidence was the total person-years of insured individuals in 2016 in the database, covering approximately 0.43 billion individuals. The numerator was the number of incident GIST cases in 2016.

RESULTS

The crude incidence in 2016 was 0.40 per 100,000 person-years (95% CI, 0.06-1.03). Male incidence was higher than female incidence (0.44 vs. 0.36, rate ratio: 1.22, p < 0.001). The mean age at diagnosis was 55.20 years (SD = 14.26) and the incidence among those aged 50 years or older was 2.63 times (0.84 vs. 0.32, p < 0.001) higher than those aged under 50. The highest incidence was observed in East China (2.29, 95% CI: 0.46-5.54).

CONCLUSIONS

The incidence of GIST in mainland China was lower than Europe, North America and Korea. The mean age at diagnosis of GIST in China was younger than that of Europe and Canada. This study provides useful information to further research, policy formulating and management of GIST.

Cost-effectiveness Analysis of Genetic Testing and Tailored First-Line Therapy for Patients With Metastatic Gastrointestinal Stromal Tumors

IMPORTANCE

Gastrointestinal stromal tumor (GIST) is frequently driven by oncogenic KIT variations. Imatinib targeting of KIT marked a new era in GIST treatment and ushered in precision oncological treatment for all solid malignant neoplasms. However, studies on the molecular biological traits of GIST have found that tumors respond differentially to imatinib dosage based on the KIT exon with variation. Despite this knowledge, few patients undergo genetic testing at diagnosis, and empirical imatinib therapy remains routine. Barriers to genetic profiling include concerns about the cost and utility of testing.

OBJECTIVE

To determine whether targeted gene testing (TGT) is a cost-effective diagnostic for patients with metastatic GIST from the US payer perspective.

DESIGN, SETTING, AND PARTICIPANTS

This economic evaluation developed a Markov model to compare the cost-effectiveness of TGT and tailored first-line therapy compared with empirical imatinib therapy among patients with a new diagnosis of metastatic GIST. The main health outcome, quality-adjusted life years (QALYs), and costs were obtained from the literature, and transitional probabilities were modeled from disease progression and survival estimates from randomized clinical trials of patients with metastatic GIST. Data analyses were conducted October 2019 to January 2020.

EXPOSURE

TGT and tailored first-line therapy.

MAIN OUTCOMES AND MEASURES

The primary outcome was QALYs and cost. Cost-effectiveness was defined using an incremental cost-effectiveness ratio, with an incremental cost-effectiveness ratio less than $100 000/QALY considered cost-effective. One-way and probabilistic sensitivity analyses were conducted to assess model stability.

RESULTS

Therapy directed by TGT was associated with an increase of 0.10 QALYs at a cost of $9513 compared with the empirical imatinib approach, leading to an incremental cost-effectiveness ratio of $92 100. These findings were sensitive to the costs of TGT, drugs, and health utility model inputs. Therapy directed by TGT remained cost-effective for genetic testing costs up to $3730. Probabilistic sensitivity analysis found that TGT-directed therapy was considered cost-effective 70% of the time.

CONCLUSIONS AND RELEVANCE

These findings suggest that using genetic testing to match treatment of KIT variations to imatinib dosing is a cost-effective approach compared with empirical imatinib.

KIT exon 11 and PDGFRA exon 18 gene mutations in gastric GIST: proposal of a short panel for predicting therapeutic response

Background

GIST is the most common mesenchymal tumor of gastrointestinal tract and is more frequent in stomach. Its main mutations affect KIT and PDGFRA genes. Full genetic analysis panels are currently used to study mutations in GIST and other tumors. Considering that in gastric GIST KIT gene mutations in exon 11 are sensitive to IM whereas PDGFRΑ gene mutations in exon 18 (D842V) are resistant to the same drug, the aim of this study is to focus on these two molecular targets as a short alternative panel for predicting therapeutic response in gastric GIST which might optimize resources.

Methods

The genotypes of 38 cases of primary GIST were determined by performing bidirectional DNA sequencing.

Results

Exon 11 of KIT gene showed mutations in 65.3% and the exon 18 of PDGFRA gene showed 9% of cases. So it was possible to determine a subgroup of tumors which presented mutations in KIT exon 11 and PDGFRA exon 18.

Conclusion

Considering all of the foregoing analyzed globally, the application of short panel has impact on the cost and time of release of results to the physician, allowing a rapid approach to patients eligible for treatment with the target therapy.

Subepithelial rectal gastrointestinal stromal tumor - the use of endoscopic ultrasound-guided fine needle aspiration to establish a definitive cytological diagnosis: a case report

Background

Gastrointestinal stromal tumors are the most common mesenchymal neoplasms affecting the gastrointestinal tract. The stomach is the most common location to be affected, and the rectum one of the rarest, but the whole gastrointestinal tract remains susceptible. Gastrointestinal stromal tumors account for only 0.1% of rectal tumors. Currently, endoscopic ultrasound plays an essential role in the diagnostic process of gastrointestinal stromal tumors, especially when the affected sites have a worse outcome and higher morbidity rates.

Case presentation

We describe the case of a 68-year-old white Japanese man with a history of long-term mild rectal pain and tenesmus. A digital rectal examination revealed a right palpable solid mass ranging from 3 to 7 cm from his anal verge. A colonoscopy was performed and showed a 5 cm elevated lesion covered by normal mucosa, located 4 cm above the pectineal line. Endoscopic ultrasound confirmed the diagnosis of a homogeneous hypoechoic mass with areas of necrosis as a rectal subepithelial lesion originating at the fourth layer (muscularis propria). He then underwent endoscopic ultrasound-guided fine needle aspiration of the lesion, followed by cytological and immunohistochemistry evaluation. The evaluation showed spindle and epithelioid cells of variable sizes, in fascicles separated by stroma, which reacted firmly and consistently to CD117/c-kit and CD34, and negative to desmin and S-100 protein. There was weak staining for nuclear Ki-67 in the tumor cells. A diagnosis of rectal gastrointestinal stromal tumor was confirmed. After a multidisciplinary meeting, an abdominoperineal resection of his rectum was performed. The pathology of the specimen confirmed the diagnosis of rectal gastrointestinal stromal tumor. He is now asymptomatic after 3 months’ follow-up and is on adjuvant therapy with a tyrosine-kinase inhibitor.

Conclusions

Gastrointestinal stromal tumors are rare tumors, and among the variety of primary location sites, the rectum is one of the rarest. The localization of this type of tumor has worse outcomes and higher morbidity rates. We report this rare case to emphasize the need for precise diagnosis and the important role of endoscopic ultrasound-guided fine needle aspiration in such situations.