- Email: [email protected]
Re: Metastatic Involvement of a Retrieved Inferior Vena Cava Filter
Volume 15
Number 7
Henri Marret, MD, and Jean-Philippe Cottier, MD, PhD Departments of Gynaecology, Obstetrics, Fetal Medecine and Human Reproduction (H.M.) and Neuroradiology (J.-P.C.) Bretonneau University Hospital 2 Boulevard Tonnellé 37044 Tours, France E-mail: [email protected]
Re: Metastatic Involvement of a Retrieved Inferior Vena Cava Filter From: John A. Kaufman, MD Dotter Interventional Institute Oregon Health & Science University L342, 3181 SW Sam Jackson Park Road Portland, OR 97201 E-mail: [email protected] Editor: The recent letter by Neeman et al (1) presents a uniquely documented case of venous tumor embolization and nicely restates the widely recognized inadequacies of our knowledge about vena cava filters. However, the letter is also an example of how an isolated fact from a single case viewed in retrospect can have undue influence on opinion. The letter was stimulated by the finding of adherent tumor cells on the struts of a retrieved vena cava filter. The patient described is a 19-year-old man with metastatic osteosarcoma and known lower-extremity deep vein thrombosis complicated by pulmonary emboli. The patient underwent placement of a retrievable vena cava filter before major lower extremity surgery with the intention to remove the device in the postoperative period. The filter was in place for 14 days. Before retrieval, the cavogram was normal. The authors were surprised to find adherent material on the filter, which on pathologic analysis included metastatic tumor cells. The authors expressed significant concern about this finding, especially that the retrieval procedure might have resulted in a shower of tumor cells, or that, left in place, the filter could have represented a locus for metastatic growth. Using this case as an example, the authors decry the liberalization of indications for filter placement and specifically characterize the introduction of retrievable filters as a potentially “dangerous situation” because of the natural tendency to further relax indications. As the authors have associated retrievable filters with the word “dangerous” in this forum, it is important to recognize in the same forum that (1) inferior vena cava filter placement in this patient was indicated; (2) retrieval of the device was performed entirely at the authors’ prerogative, and, based on the timing of publication, probably represented an offlabel application; (3) small amounts of adherent material are commonly found on retrieved vena cava filters despite clean appearance on cavograms; and (4) only a portion of the originally blood-borne tumor cells could have stopped on the filter struts; most probably passed through the device. Worrying about the release of tumor cells during filter removal, or the possibility for local growth of a metastatic
DOI: 10.1097/01.RVI.0000133555.17746.57
Letters to the Editor
•
775
deposit should the filter not have been retrieved, fails to acknowledge the true implication of their finding: that tumor cells in greater numbers have already been hematogenously delivered to the lungs. Last, the indications for filter retrieval in this patient are not readily apparent from the data provided in the letter: in the setting of metastatic osteosarcoma (even before the hematogenous shower), deep vein thrombosis with pulmonary emboli, and major surgery, why take the filter out? Were there objective data to support high probability of cure and normal life expectancy in this patient? The authors’ use of this case as a springboard for generalized commentary on vena cava filters is one more example of the largely retrospective non– hypothesis-based literature on filters. All optional vena cava filters are approved for permanent implantation, so retrieval is never mandatory. Approval for retrieval has been granted without change in current indications for placement, or the addition of indications for retrieval. Despite the weakness of existing data, it is safe to conclude that the risk of complications resulting from filters in the inferior vena cava increases with time (2). In the absence of rigorous scientific evidence, removal of this type of vena cava filter should be considered only in patients who exhibit stability with first-line therapy (anticoagulation) or prophylaxis for venous thromboembolic disease during the optional period of the device, are unlikely to require subsequent caval interruption in the near future, and who have reasonable life expectancies. Most importantly, the decision to retrieve a filter should always be individualized and include a balanced assessment of current and future risk. References 1. Neeman Z, Auerbach A, Wood BJ. Metastatic involvement of a retrieved inferior vena cava filter. J Vasc Interv Radiol 2003; 14:1585. 2. Decousus H, Leizorovicz A, Parent F, et al. A clinical trial of vena caval filters in the prevention of pulmonary embolism in patients with proximal deep-vein thrombosis. Prevention du Risque d’Embolie Pulmonaire par Interruption Cave Study Group. N Engl J Med 1998; 338:409 – 415.
Drs Neeman and Wood respond: We are pleased our letter to the editor has generated such a thoughtful response from our distinguished colleague, Dr. Kaufman, who is an expert in this area (1). Overall, we have very similar opinions. We were in no way attempting to “influence opinions”, as suggested. We had an interesting finding of metastases to a temporary filter that raised some questions and wanted to present those questions to the Journal of Vascular and Intervascular Radiology readership. Indications for temporary filters are controversial and without multidisciplinary consensus. As Dr. Kaufman states, there are inadequacies in our knowledge about vena cava filters. We strongly believe in the clinical role of filters, but feel that caution is advised as temporary filters saturate the market. Several important pieces of information were absent from Dr. Kaufman’s letter that respectfully deserve mention. Most important, the 19-year-old patient in our study is alive and disease-free 21 months after filter removal, enjoying school and a normal life, free of venous symptoms. Dr. Kaufman implies that filter removal was not indicated in
DOI: 10.1097/01.RVI.0000133556.86268.A6
776
•
Letters to the Editor
this patient. To answer his question: yes, there are data to suggest that cure and a normal life expectancy are possible for this patient. To condemn all cancer patients to permanent filter placement just because the statistics of their cancer are unfavorable is bad medicine. Cancer patients often receive substandard care because of assumptions regarding life expectancy and cure. Permanent filter placement could subject these patients to fairly common long-term complications. Our patient was 19-years-old (2). The SIR quality improvement guidelines for 2003 state in the section on contraindictions: “for pediatric and young adult patients, filter placement indications should be strict because the long term effects and durability of the devices are not precisely known” (3). Dr. Kaufman’s comments about retrospective, non-hypothesis driven literature are accurate. This was exactly our main point. Dr. Kaufman states that removal of a filter should be considered only in patients who “. . . are unlikely to require subsequent caval interruption in the near future and who have reasonable life expectancies.” Who defines reasonable? With improved more reliable temporary devices available today, safe removal of temporary filters may be performed within a limited time-window and even repeated as needed. There is an important clinical role for temporary filters that needs to be defined. We believe in the principle so much that we are developing a prototype temporary filter that may have advantages over those currently available. The details of this particular case are less important than the underlying principles. The temperospatial evolution of cancer is a poorly understood process. Millions of cancer cells are often circulating in the bloodstream (even with some small primary tumors) and are cleared by the immune
July 2004
JVIR
system. The exact process of metastatic spread is poorly defined. Thus, it is possible that a foreign body like a filter could alter the pattern of spread in some way, similar to a nidus for infection. As Dr. Kaufman states, hematogenous showering of cells to the lungs may have occurred concurrently, but lung disease has subsequently responded to therapy. The question remaining is whether local filter tumor would have responded to therapy as well. Designing trials to study treatments that could be considered standard practice is admittedly difficult. Practice patterns driven by pragmatism often dictate standards of care in the absence of scientific proof, but such is life. We should not become complacent and allow this paradigm to relegate academic medicine to the reporting of clinical practice, lest we become reporters instead of scientists. References 1. Kaufman JA. Re: Metastatic involvement of a retrieved inferior vena cava filter. J Vasc Interv Radiol 2004; 15:775. 2. Neeman Z, Auerbach A, Wood BJ. Metastatic involvement of a retrieved inferior vena cava filter. J Vasc Interv Radiol 2003; 14:1585. 3. Grassi CJ, Swan TL, Cardella JF, et al. Society of Interventional Radiology Standards of Practice Committee: quality improvement guidelines for percutaneous permanent inferior vena cava filter placement for the prevention of pulmonary embolism. J Vasc Interv Radiol 2003; 14(9 part 2):S271–S275.
Ziv Neeman, MD and Bradford J. Wood, MD Department of Radiology/Special Procedures, N.I.H, 10 Center Drive, Building 10, Clinical Center, Room 1C 660, Bethesda, MD; E-mail: [email protected]
Number 7
Henri Marret, MD, and Jean-Philippe Cottier, MD, PhD Departments of Gynaecology, Obstetrics, Fetal Medecine and Human Reproduction (H.M.) and Neuroradiology (J.-P.C.) Bretonneau University Hospital 2 Boulevard Tonnellé 37044 Tours, France E-mail: [email protected]
Re: Metastatic Involvement of a Retrieved Inferior Vena Cava Filter From: John A. Kaufman, MD Dotter Interventional Institute Oregon Health & Science University L342, 3181 SW Sam Jackson Park Road Portland, OR 97201 E-mail: [email protected] Editor: The recent letter by Neeman et al (1) presents a uniquely documented case of venous tumor embolization and nicely restates the widely recognized inadequacies of our knowledge about vena cava filters. However, the letter is also an example of how an isolated fact from a single case viewed in retrospect can have undue influence on opinion. The letter was stimulated by the finding of adherent tumor cells on the struts of a retrieved vena cava filter. The patient described is a 19-year-old man with metastatic osteosarcoma and known lower-extremity deep vein thrombosis complicated by pulmonary emboli. The patient underwent placement of a retrievable vena cava filter before major lower extremity surgery with the intention to remove the device in the postoperative period. The filter was in place for 14 days. Before retrieval, the cavogram was normal. The authors were surprised to find adherent material on the filter, which on pathologic analysis included metastatic tumor cells. The authors expressed significant concern about this finding, especially that the retrieval procedure might have resulted in a shower of tumor cells, or that, left in place, the filter could have represented a locus for metastatic growth. Using this case as an example, the authors decry the liberalization of indications for filter placement and specifically characterize the introduction of retrievable filters as a potentially “dangerous situation” because of the natural tendency to further relax indications. As the authors have associated retrievable filters with the word “dangerous” in this forum, it is important to recognize in the same forum that (1) inferior vena cava filter placement in this patient was indicated; (2) retrieval of the device was performed entirely at the authors’ prerogative, and, based on the timing of publication, probably represented an offlabel application; (3) small amounts of adherent material are commonly found on retrieved vena cava filters despite clean appearance on cavograms; and (4) only a portion of the originally blood-borne tumor cells could have stopped on the filter struts; most probably passed through the device. Worrying about the release of tumor cells during filter removal, or the possibility for local growth of a metastatic
DOI: 10.1097/01.RVI.0000133555.17746.57
Letters to the Editor
•
775
deposit should the filter not have been retrieved, fails to acknowledge the true implication of their finding: that tumor cells in greater numbers have already been hematogenously delivered to the lungs. Last, the indications for filter retrieval in this patient are not readily apparent from the data provided in the letter: in the setting of metastatic osteosarcoma (even before the hematogenous shower), deep vein thrombosis with pulmonary emboli, and major surgery, why take the filter out? Were there objective data to support high probability of cure and normal life expectancy in this patient? The authors’ use of this case as a springboard for generalized commentary on vena cava filters is one more example of the largely retrospective non– hypothesis-based literature on filters. All optional vena cava filters are approved for permanent implantation, so retrieval is never mandatory. Approval for retrieval has been granted without change in current indications for placement, or the addition of indications for retrieval. Despite the weakness of existing data, it is safe to conclude that the risk of complications resulting from filters in the inferior vena cava increases with time (2). In the absence of rigorous scientific evidence, removal of this type of vena cava filter should be considered only in patients who exhibit stability with first-line therapy (anticoagulation) or prophylaxis for venous thromboembolic disease during the optional period of the device, are unlikely to require subsequent caval interruption in the near future, and who have reasonable life expectancies. Most importantly, the decision to retrieve a filter should always be individualized and include a balanced assessment of current and future risk. References 1. Neeman Z, Auerbach A, Wood BJ. Metastatic involvement of a retrieved inferior vena cava filter. J Vasc Interv Radiol 2003; 14:1585. 2. Decousus H, Leizorovicz A, Parent F, et al. A clinical trial of vena caval filters in the prevention of pulmonary embolism in patients with proximal deep-vein thrombosis. Prevention du Risque d’Embolie Pulmonaire par Interruption Cave Study Group. N Engl J Med 1998; 338:409 – 415.
Drs Neeman and Wood respond: We are pleased our letter to the editor has generated such a thoughtful response from our distinguished colleague, Dr. Kaufman, who is an expert in this area (1). Overall, we have very similar opinions. We were in no way attempting to “influence opinions”, as suggested. We had an interesting finding of metastases to a temporary filter that raised some questions and wanted to present those questions to the Journal of Vascular and Intervascular Radiology readership. Indications for temporary filters are controversial and without multidisciplinary consensus. As Dr. Kaufman states, there are inadequacies in our knowledge about vena cava filters. We strongly believe in the clinical role of filters, but feel that caution is advised as temporary filters saturate the market. Several important pieces of information were absent from Dr. Kaufman’s letter that respectfully deserve mention. Most important, the 19-year-old patient in our study is alive and disease-free 21 months after filter removal, enjoying school and a normal life, free of venous symptoms. Dr. Kaufman implies that filter removal was not indicated in
DOI: 10.1097/01.RVI.0000133556.86268.A6
776
•
Letters to the Editor
this patient. To answer his question: yes, there are data to suggest that cure and a normal life expectancy are possible for this patient. To condemn all cancer patients to permanent filter placement just because the statistics of their cancer are unfavorable is bad medicine. Cancer patients often receive substandard care because of assumptions regarding life expectancy and cure. Permanent filter placement could subject these patients to fairly common long-term complications. Our patient was 19-years-old (2). The SIR quality improvement guidelines for 2003 state in the section on contraindictions: “for pediatric and young adult patients, filter placement indications should be strict because the long term effects and durability of the devices are not precisely known” (3). Dr. Kaufman’s comments about retrospective, non-hypothesis driven literature are accurate. This was exactly our main point. Dr. Kaufman states that removal of a filter should be considered only in patients who “. . . are unlikely to require subsequent caval interruption in the near future and who have reasonable life expectancies.” Who defines reasonable? With improved more reliable temporary devices available today, safe removal of temporary filters may be performed within a limited time-window and even repeated as needed. There is an important clinical role for temporary filters that needs to be defined. We believe in the principle so much that we are developing a prototype temporary filter that may have advantages over those currently available. The details of this particular case are less important than the underlying principles. The temperospatial evolution of cancer is a poorly understood process. Millions of cancer cells are often circulating in the bloodstream (even with some small primary tumors) and are cleared by the immune
July 2004
JVIR
system. The exact process of metastatic spread is poorly defined. Thus, it is possible that a foreign body like a filter could alter the pattern of spread in some way, similar to a nidus for infection. As Dr. Kaufman states, hematogenous showering of cells to the lungs may have occurred concurrently, but lung disease has subsequently responded to therapy. The question remaining is whether local filter tumor would have responded to therapy as well. Designing trials to study treatments that could be considered standard practice is admittedly difficult. Practice patterns driven by pragmatism often dictate standards of care in the absence of scientific proof, but such is life. We should not become complacent and allow this paradigm to relegate academic medicine to the reporting of clinical practice, lest we become reporters instead of scientists. References 1. Kaufman JA. Re: Metastatic involvement of a retrieved inferior vena cava filter. J Vasc Interv Radiol 2004; 15:775. 2. Neeman Z, Auerbach A, Wood BJ. Metastatic involvement of a retrieved inferior vena cava filter. J Vasc Interv Radiol 2003; 14:1585. 3. Grassi CJ, Swan TL, Cardella JF, et al. Society of Interventional Radiology Standards of Practice Committee: quality improvement guidelines for percutaneous permanent inferior vena cava filter placement for the prevention of pulmonary embolism. J Vasc Interv Radiol 2003; 14(9 part 2):S271–S275.
Ziv Neeman, MD and Bradford J. Wood, MD Department of Radiology/Special Procedures, N.I.H, 10 Center Drive, Building 10, Clinical Center, Room 1C 660, Bethesda, MD; E-mail: [email protected]