Adjuvant radiotherapy for gastrointestinal stromal tumor of the rectum

Radiotherapy in the management of rare gastrointestinal cancers: A systematic review

The aim of this analysis is to assess radiotherapy's role and technical aspects in an array of rare gastrointestinal (GI) cancers for adult patients. Collection data pertaining to radiotherapy and digestive rare cancers were sourced from Medline, EMBASE, and Cochrane Library. Preoperative chemoradiotherapy improved outcomes for patients with esophageal undifferentiated carcinoma compared with esophageal salivary gland types of carcinomas. For rare gastric epithelial carcinoma, perioperative chemotherapy is the common treatment. Adjuvant chemoradiotherapy showed no benefice compared with adjuvant chemotherapy for duodenal adenocarcinoma. Small bowel sarcomas respond well to radiotherapy. By analogy to anal squamous cell carcinoma, exclusive chemoradiotherapy provided better outcomes for patients with rectal squamous cell carcinoma. For anal adenocarcinoma, neoadjuvant chemoradiotherapy, followed by radical surgery, was the most effective regimen. For pancreatic neuroendocrine tumors, chemoradiotherapy can be a suitable option as postoperative or exclusive for unresectable/borderline disease. The stereotactic body radiotherapy (SBRT) is a promising approach for hepatobiliary malignancy. Radiotherapy is a valuable option in gastrointestinal stromal tumors (GIST) for palliative intent, tyrosine kinase inhibitors (TKIs) resistant disease, and unresectable or residual disease. Involved field (IF) radiotherapy for digestive lymphoma provides good results, especially for gastric extranodal marginal zone lymphoma (MALT). In conclusion, radiotherapy is not an uncommon indication in this context. A multidisciplinary approach is needed for better management of digestive rare cancers.

Colonic schwannoma: A case of unusual presentation and outcome

Background: Schwannomas are mesenchymal tumors arising from neural sheath cells and whose diagnosis is based on immunohistochemistery. The digestive and especially colonic location of this tumor is rare. Commonly described in elderly patient, their malignancy is unusual. Case report: We report the case of a 23-year-old girl, with learning disability, operated in emergency for acute peritonitis. Peroperatively, we discovered a peritonitis secondary to a bulky perforated cecal tumor. We performed a right colectomy and an ileostomy. The posterior margin of the resection was macroscopically involved. The diagnosis of colonic schwannoma was confirmed with immunopathological examination of the surgical specimen. Surgical exploration 4 months later and morphological investigations during 2 years showed stability of the tumoral residue in the right iliac fossa. However, we noticed, on CT scanning control 2 years postoperatively, the appearance of a mesenteric recurrence. Exploratory laparotomy confirmed the unresectability of this mesenteric mass and showed the presence of multiple parietal nodules whose biopsies revealed their neurofibromatous nature. The 4 year follow-up of the patient didn’t reveal any complication rather than need to right nephrostomy due to ureter compression by the primary tumoral residue. Discussion: Colonic schwannoma is a rare disease, commonly described in uncomplicated stages. The learning disability of our patient had favorized the absence of declared symptoms and promoted the evolution of the cecal swhannoma until its perforation. This complication was not described before. Local recurrence has been also rarely reported in the literature. Association with neurofibroma may be hereditary in a context of neurofibromatosis or sporadic. Conclusion: Colonic schwannoma may have polymorphic presentation mimicking malignant tumor in such cases. Not treated in time, it can lead to severe complications, such as tumoral perforation. Surgical resection remains the mainstay treatment. The slow evolutionary genius of schwannoma, even when incompletely resected by necessity, confirms its good prognosis.

Radiotherapy in the Management of Gastrointestinal Stromal Tumors: A Systematic Review

Simple Summary

Gastrointestinal stromal tumors are considered to be insensitive to radiotherapy. However, with the development of radiation techniques and the accumulation of cases, some studies have indicated that radiotherapy could help achieve objective response in advanced or metastatic gastrointestinal stromal tumors. Therefore, it is necessary to conduct a systematic review to reassess the role of radiotherapy in gastrointestinal stromal tumors. The purpose of this study was to draw the attention of scholars and clinicians to radiotherapy and promote further research on radiotherapy in gastrointestinal stromal tumors.

Abstract

Gastrointestinal stromal tumors (GISTs) are considered insensitive to radiotherapy. However, a growing number of case reports and case series have shown that some lesions treated by radiotherapy achieved an objective response. The aim of the study was to perform a systematic review of all reported cases, case series, and clinical studies of GISTs treated with radiotherapy to reevaluate the role of radiotherapy in GISTs. A systematic search of the English-written literature was conducted using PubMed, Web of Science, and Embase databases. Overall, 41 articles describing 112 patients were retrieved. The included articles were of low to moderate quality. Bone was the most common site treated by radiotherapy, followed by the abdomen. In order to exclude the influence of effective tyrosine kinase inhibitors (TKIs), a subgroup analysis was conducted on whether and which TKIs were concurrently applied with radiotherapy. Results showed that radiotherapy alone or combined with resistant TKIs could help achieve objective response in selected patients with advanced or metastatic GISTs; however, survival benefits were not observed in the included studies. Pain was the most common symptom in symptomatic GISTs, followed by neurological dysfunction and bleeding. The symptom palliation rate was 78.6% after excluding the influence of effective TKIs. The adverse reactions were mainly graded 1–2. Radiotherapy was generally well-tolerated. Overall, radiotherapy may relieve symptoms for GIST patients with advanced or metastatic lesions and even help achieve objective response in selected patients without significantly reducing the quality of life. In addition to bone metastases, fixed abdominal lesions may be treated by radiotherapy. Publication bias and insufficient quality of included studies were the main limitations in this review. Further clinical studies are needed and justified.

Recent Advancements in the Treatment of Rectal Gastrointestinal Stromal Tumor: In Era of Imatinib

Gastrointestinal stromal tumors (GIST) are the most common mesenchymal tumor of the gastrointestinal tract, with an annual incidence of 10–15 cases per million. However, rectal GIST has a low incidence, accounting for approximately 0.1% of all rectal tumors. The treatment of rectal GISTs is still controversial and the relative unified guidelines and consensus opinions are inadequate. Treatment is based primarily on the clinical experience of the physician. The widespread application of neoadjuvant imatinib therapy allows diversification of treatment, especially in the choice of surgical methods. Herein, we reviewed the most recent literature and summarized the new progress in rectal tumor treatment, with the aim of providing patients with more systematic and individualized therapeutic strategies.

Simultaneous Integrated Boost Intensity-Modulated Radiotherapy for Locally Advanced Drug-Resistant Gastrointestinal Stromal Tumors: A Feasibility Study

Background

As an emerging clinical problem, locally advanced drug-resistant gastrointestinal stromal tumors (LADRGISTs) has relatively few therapeutic schemes. Although radiotherapy is not often considered for GISTs, it could be a valuable contributing modality. The aim of our study is to explore a safe and effective radiation regimen for LADR-GISTs.

Methods

Three patients with LADR-GISTs were treated with simultaneous integrated boost intensity-modulated radiation therapy (SIB-IMRT) plans. In the SIB-IMRT plans, gross target volume (GTV) was divided into GTV-outer, GTV-mid, and GTV-center. And the prescribed dose of planning gross target volume (PGTV) and GTV-outer were both set to 50.4 Gy in 28 fractions. GTV-mid and GTV-center were simultaneously boosted to 60–62 Gy and 62–64 Gy respectively. For comparison purposes, conventional IMRT (Con-IMRT) plans with uniform dose distribution were generated for same optimization objectives without a dose boost to GTV-mid and GTV-center. All plans were optimized to make sure that deliver at least 95% of the prescription dose was delivered to PGTV. Isodose distribution, dose profiles, conformity indexes (CIs), monitor units (MUs), and dose volume histogram (DVH) was evaluated for each individual patient. After the three patients were treated with SIB-IMRT plans, the relative changes in the tumor size and CT values by CT scanning were also tracked.

Results

Compared with Con-IMRT plans, SIB-IMRT plans saw a significant increase from D₉₅ to D₂ of the GTV. With steeper dose gradients in the dose profiles, SIB-IMRT plans had GTV-mid and GTV-center accumulated with higher dose mainly by delivering extra 93 MUs in average. However, there was no significant difference in CIs and organs at risks (OARs) DVH. The relative changes in tumor size and CT values of the three patients in follow up were up to the Choi criteria and the three patients were all assessed as partial response.

Conclusions

The proposed SIB-IMRT may be a potential technique for achieving objective response and prolonging survival of selected GISTs patients.

Radiotherapy for Gastrointestinal Stromal Tumors

OBJECTIVE

Gastrointestinal stromal tumors (GISTs) are rare mesenchymal tumors of the gastrointestinal tract, which frequently cause intraabdominal metastases. The current standard of care is surgery for localized cases, and adjuvant imatinib is recommended for tumors with a high risk of recurrence. To date, radiotherapy has not been commonly accepted as a part of multimodality treatment approach other than palliation. However, recently published case reports and some small series suggest that radiotherapy is a valuable option for controlling locally progressive, drug-resistant disease. The aim of this review is to provide a viewpoint from a radiation oncologist concerning the management of GISTs, especially rectal GIST, and clarify the role and technical aspects of radiotherapy in the treatment approach.

DATA SOURCES

A comprehensive search in PubMed using the keywords "radiotherapy for rectal GIST" and "rectal GIST" was undertaken. The literature search included the related articles after 1995.

STUDY SELECTION

The main articles including rectal GIST case reports and GIST series containing rectal cases were the primary references.

RESULTS

Surgery is the mainstay of treatment. However, to date, radiotherapy is included in the multidisciplinary treatment strategy of rectal GISTs in some circumstances with palliative, adjuvant, or definitive intent using different treatment doses and fields.

CONCLUSIONS

Recently reported long-term local control rates indicate that GIST is a radiosensitive disease. This makes radiotherapy a valuable alternative in GIST management with curative intent, especially in patients who (1) cannot tolerate or are resistant to chemotherapy agents, (2) have an unresectable disease, (3) have a gross or microscopic residual disease after surgery, and (4) have a recurrent disease.

Local excision of rectal schwannoma using transanal endoscopic microsurgery: A case report

INTRODUCTION

Schwannoma is a neoplasm originating from the neural crest cells (schwann cells) that form nerve sheaths. These tumors are thought to be benign with little risk of malignant transformation. They rarely affect the gastrointestinal tract, and primary rectal involvement is extremely rare. Until 2013, only 11 cases of anorectal schwannoma have been reported. Optimal surgical treatment of rectal schwannoma has not been established.

PRESENTATION OF CASE

We herein describe a 70-year-old woman with a submucosal tumor arising from the posterior wall of the rectum with features mimicking a gastrointestinal stromal tumor. After discussing the operative procedures and obtaining written informed consent, we attempted local excision of the tumor using a transanal endoscopic microsurgery (TEM). The tumor was proved to be S-100 positive schwannoma on immuhistochemical studies. Her postoperative course was uneventful, and there is no evidence of tumor recurrence as of 6 months after surgical excision.

DISCUSSION

An extremely rare rectal schwannoma was successfully treated using a TEM without compromising anorectal function.

CONCLUSION

TEM is a feasible approach for local excision of rectal tumors with low risk of malignancy.

Considering the role of radiation therapy for gastrointestinal stromal tumor

Gastrointestinal stromal tumors (GISTs) are rare mesenchymal tumors arising in the gastrointestinal tract. Over the last decade, the management and prognosis of GISTs has changed dramatically with molecular characterization of the c-kit mutation and the adoption of targeted systemic therapy. Currently, the standard of care for resectable tumors is surgery, followed by adjuvant imatinib for tumors at high risk for recurrence. Inoperable or metastatic tumors are treated primarily with imatinib. Despite excellent initial response rates, resistance to targeted therapy has emerged as a common clinical problem, with relatively few therapeutic solutions. While the treatment of GISTs does not commonly include radiotherapy, radiation therapy could be a valuable contributing modality. Several case reports indicate that radiation can control locally progressive, drug-resistant disease. Further study is necessary to define whether radiation could potentially prevent or delay the onset of drug resistance, or improve outcomes when given in combination with imatinib.

Abdominal schwannomas: case report with literature review

Schwannomas are rare tumors that arise from Schwann cells in neural sheaths. They are commonly found in the central nervous system, spinal cord, or peripheral nerves of the body. Occasionally, they occur in the gastrointestinal tract, with the stomach being the most common site. However, colorectal and retroperitoneal schwannomas are very rare. Preoperative diagnosis is often difficult and definitive treatment entails surgical excision. We herein present 3 cases of intraabdominal schwannomas.

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Gastrointestinal stromal tumors (GISTs) are known to be poorly responsive to conventional chemotherapy and historically considered resistant to radiotherapy. In the past the mainstay of GIST treatment was surgery, but the introduction of tyrosine kinase inhibitors (TKIs) imatinib and sunitinib marked the beginning of a new era in the treatment of GIST patients. To date, radiotherapy for GIST has not been administered in clinical practice except for limited palliative settings and there are no clear data on the administration of radiotherapy, alone or in combination with TKIs, with a purely cytoreductive intent. We describe the clinical case of a 48-year-old woman with metastatic GIST treated with external radiotherapy in a critical supraclavicular tumor localization progressively increasing in size with several symptoms and not responsive to systemic TKI therapies. We obtained an initial shrinkage of the mass and subsequent stabilization with an immediate and clear clinical benefit. Although the historical medical literature considered GISTs resistant to radiation therapy, our clinical case suggests this treatment may be appropriate in selected patients.

Schwannoma of ascending colon treated by laparoscopic right hemicolectomy

Schwannomas of the colon are rare and are difficult to diagnose preoperatively, since they often defy endoscopic and radiographic detection. Immunohistochemical stains are useful postoperatively to confirm this tumor, but more reliable diagnostic techniques (such as colonoscopic biopsy with immunohistochemistry) have emerged to enhance preoperative diagnostic accuracy. Here we report an instance of schwannoma arising in the ascending colon, where immunohistochemical staining of a preoperative biopsy facilitated diagnosis. After laparoscopic resection, histologic examination was confirmatory.

Radiotherapy in the treatment of gastrointestinal stromal tumor

Gastrointestinal stromal tumors (GISTs) are uncommon mesenchymal tumors of the gastrointestinal tract. Up to one-third of GISTs are malignant with a high rate of metastasis. Surgical resection is the mainstay of care for patients with resectable disease. Imatinib mesylate, a selective tyrosine kinase inhibitor, is the current standard of care for GISTs that cannot be completely resected or in cases of metastatic GIST. Although often overlooked, radiation therapy is a viable option for select patients with GIST. We report the case of a patient with unresectable GIST who was treated with local radiotherapy and achieved long-term response. We also present a review of the literature regarding the use of radiotherapy in the treatment of GIST. GIST has been shown to be a radiosensitive tumor. Radiotherapy can offer long-term local control and should be considered in the adjuvant or palliative setting. The role of radiotherapy delivered concurrently with imatinib in the treatment of GIST may warrant further investigation.

Gastrointestinal stromal tumor of the rectum: an analysis of seven cases

PURPOSE

Gastrointestinal stromal tumors (GISTs) rarely originate in the rectum. We investigated the clinicopathologic characteristics of rectal GISTs.

METHODS

We analyzed the medical records of seven patients who underwent surgery for GIST of the rectum between 1998 and 2003.

RESULTS

There were two men and five women with a median age of 55 years (range, 41-72 years) at the time of diagnosis. The median follow-up period was 23 months (range, 7-75 months). The chief symptoms were hematochezia, constipation, and anal pain. All patients underwent curative resection; in the form of abdominoperineal resection in five patients, transanal excision in one, and Hartmann's operation with prostatectomy in one. The median tumor size was 6.6 cm (range, 1-12 cm). Four patients received adjuvant radiation therapy. Local recurrence developed in two patients; 54 months and 23 months after surgery, respectively.

CONCLUSION

The common symptoms of rectal GIST were the same as those of other rectal tumors. Curative surgical resection should be done, but further studies are necessary to investigate better adjuvant treatment strategies for patients with rectal GISTs.

Gastrointestinal stromal tumor of the anal canal: an unusual presentation

BACKGROUND

Gastrointestinal stromal tumors (GIST) of the stomach are the most frequent followed by those of the intestinal tract, while colon and rectum represent rare sites. GIST of the anal canal are extremely rare. They have been studied along with GIST of the rectum, as a single entity, and along with them they represent 5% of GIST. GIST arising from the anal canal account for only 2%-8% of the anorectal GIST. Thus anal GIST must be considered an exceptional case.

CASE PRESENTATION

A 78-year-old man was referred to our Institution for an anal mass, in absence of any symptom. The patient was treated by local excision. An histological diagnosis of a low grade GIST was made. No further treatment was necessary. No local recurrence of distant metastases were found at follow-up.

CONCLUSION

At the moment, only ten cases of c-kit positive anal GIST are reported in the literature. These few data are not sufficient to establish a widely accepted approach for this neoplasia. We recommend to perform an initial local excision, to define the risk of aggressive behavior and the resection margins and proceed to a more aggressive treatment, if the GIST belongs to high or very high risk group. The role of adjuvant therapy is still uncertain. Although inhibitors of tyrosine-kinase receptor needs further studies before their routine use, their role in case of distant or local recurrence has been accepted. Patients' close follow up is mandatory to disclose as soon as possible local recurrences or metastases.

Interstitial cells of Cajal in health and disease. Part II: ICC and gastrointestinal stromal tumours

Mesenchymal tumours in the gastrointestinal tract have long been problematic in terms of diagnosis, prognosis and therapy, but recent advances in immunohistochemistry and related therapies have allowed more specific diagnosis. In particular, the recognition that both the interstitial cells of Cajal (ICC) and many gastrointestinal stromal tumours (GISTs) are positive for c-kit and CD34 and have other features similar to those of ICC has led to the use of imatinib, a novel small molecule therapy that blocks the CD117/c-kit tyrosine kinase receptor, which shows remarkable efficacy in treatment of malignant and metastatic GISTs as well as other malignancies.

Imatinib mesylate in the treatment of gastrointestinal stromal tumour

Imatinib mesylate is a selective and potent small-molecule inhibitor of tyrosine kinases, including Kit, platelet-derived growth factor receptor, and the BCR-Abl fusion protein. Kit plays an important role in gastrointestinal stromal tumours (GISTs) and is one of the most exciting therapeutic targets discovered so far. Clinical trials have consistently shown the dramatic efficacy of imatinib mesylate in patients with GIST. This article will review the development and pharmacology of this small-molecule inhibitor and summarise the clinical trials of imatinib mesylate for the treatment of GIST. Although imatinib mesylate has significantly improved the outcomes of most patients with advanced GIST, unanswered questions remain: what is the role of imatinib mesylate in the pre- and postoperative settings? What is the mechanism of the antitumour activity of imatinib? How do you manage patients whose tumours are refractory to imatinib mesylate?

Sigmoid schwannoma: A rare case

Schwannomas are rare tumors derived from the cells of Schwann that form the neural sheath. When located in the gastrointestinal tract, they constitute together with leiomyoma, leiomyoblastoma, and leiomyosarcoma, the gastrointestinal stromal tumors (GIST). Peripheral nerve sheath tumors represent 2-6% GIST with most common location, the stomach and the small intestine. Schwannomas of the colon and rectum are extremely rare and radical excision with wide margins is mandatory, due to their tendency to recur locally and become malignant, if left untreated. In the present study, we report a rare case of a sigmoid schwannoma, which was successfully treated in our department and reviewed the literature.

The role of surgery in the management of gastrointestinal stromal tumors (GISTs) in the era of imatinib mesylate effectiveness

Surgical resection is the treatment of choice for the gastrointestinal stromal tumors (GISTs). In the literature, the 5-year patient survival after surgical resection, ranged from 48 to 80%, before the era of imatinib mesylate and the exploration of the prognostication criteria. Imatinib mesylate targets an intracellular signaling molecule of the natural history and malignant development of GISTs, and increased the 5-year survival rate, after the resection of primary low-risk GISTs, to similar values to the normal population. For high-risk GISTs, current knowledge which is still under expansion, show major improvement at the 1-year survival rate of more than 90% versus less than 50% before imatinib era. After surgical resection, for both low and high malignant potential GISTs, a closed control directed to the early identification of confined resectable recurrences, is required. This paper assesses the current knowledge of GIST management, motivated by a case of patient with intermediate risk GIST.

Normal and Oncogenic Forms of the Receptor Tyrosine Kinase Kit

Kit is a receptor tyrosine kinase (RTK) that binds stem cell factor. This receptor ligand combination is important for normal hematopoiesis, as well as pigmentation, gut function, and reproduction. Structurally, Kit has both an extracellular and intracellular region. Theintra-cellular region is comprised of a juxtamembrane domain (JMD), a kinase domain, a kinase insert, and a carboxyl tail. Inappropriate expression or activation of Kit is associated with a variety of diseases in humans. Activating mutations in Kit have been identified primarily in the JMD and the second part of the kinase domain and have been associated with gastrointestinal stromal cell tumors and mastocytosis, respectively. There are also reports of activating mutations in some forms of germ cell tumors and core binding factor leukemias. Since the cloning of the Kit ligand in the early 1990s, there has been an explosion of information relating to the mechanism of action of normal forms of Kit as well as activated mutants. This is important because understanding this RTK at the biochemical level could assist in the development of therapeutics to treat primary and secondary defects in the tissues that require Kit. Furthermore, understanding the mechanisms mediating transformation of cells by activated Kit mutants will help in the design of interventions for human disease associated with these mutations. The objective of this review is to summarize what is known about normal and oncogenic forms of Kit. We will place particular emphasis on recent developments in understanding the mechanisms of action of normal and activated forms of this RTK and its association with human disease, particularly in hematopoietic cells.

The GIST of targeted cancer therapy: a tumor (gastrointestinal stromal tumor), a mutated gene (c-kit), and a molecular inhibitor (STI571)

Although gastrointestinal stromal tumor (GIST) is the most frequent mesenchymal neoplasm of the gastrointestinal tract, until recently it has been an obscure disease. Now, there is widespread scientific and clinical interest in GIST because its principal pathogenetic defect has been identified and a specific molecular inhibitor of GIST has been developed. Most GISTs contain a gain-of-function mutation in the c-kit proto-oncogene. Mutation results in constitutive activation of the Kit receptor tyrosine kinase, which induces cellular proliferation. STI571 is an oral agent that selectively inhibits Kit. It is a landmark development in cancer treatment and marks a new era of targeted molecular therapy. Its efficacy proves that a specific inhibitor can counteract the effects of a genetic defect responsible for neoplasia. Although STI571 was first applied to GIST only 2 years ago, it has already revolutionized the treatment of patients with metastatic disease and is also currently being tested as an adjuvant therapy after the resection of primary GIST.

Clinical management of gastrointestinal stromal tumors: before and after STI-571

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal neoplasm of the gastrointestinal tract. Until recently, surgery has been the only effective therapy for GIST. However, even after complete resection of tumor, many patients still eventually die of disease recurrence. Conventional chemotherapy and radiation therapy have been of limited value. Within the last few years, it was discovered that most GISTs have a gain-of-function mutation in the c-kit proto-oncogene. This results in ligand-independent activation of the KIT receptor tyrosine kinase and an unopposed stimulus for cell growth. STI-571 is a small molecule that selectively inhibits the enzymatic activity of the ABL, platelet-derived growth factor receptor, and KIT tyrosine kinases and the BCR-ABL fusion protein and is a landmark development in cancer therapy. Its clinical development marks a new era of rational and targeted molecular inhibition of cancer that emanates from direct collaborations between scientists and clinicians. It provides proof of the principle that a specific molecular inhibitor can drastically and selectively alter the survival of a neoplastic cell with a particular genetic aberration. The advent of STI-571 has markedly altered the clinical approach to GIST. It has proven to be effective in metastatic GIST and is also under investigation as a neoadjuvant and adjuvant therapy.

Gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are mesenchymal gut tumors that differ dramatically from other histologically similar neoplasms, such as leimomyomas, leiomyosarcomas (LMS), and neural tumors. Complete surgical removal remains the best current therapy for GISTs, but even major resections are associated with recurrence in approximately 90% of cases. GISTs are remarkably resistant to irradiation and standard chemotherapy; there is no role for treatment with those modalities. Treatment of advanced GIST patients with STI571, a novel selective tyrosine kinase inhibitor, results in remission rates that approach 60% and overall tumor control rates of 85%. Selected groups of patients, as based on tumor mutational status, have response rates as high as 80%. To date, STI571 therapy remains the only systemic treatment for GISTs to have meaningful clinical activity. Though other molecularly targeted therapies exist in oncology (eg, trastuzumab), STI571 is one of the first that applies a drug specifically designed to inhibit the product of a constitutively-activating mutation that drives pathogenesis of a solid tumor. Its use can serve as a paradigm for designing molecularly targeted therapies for other malignancies.