LETTER TO THE EDITOR
Mechanisms behind intracoronary radiation therapy failure
Francis Q. Almeda, MD* and
Gary L. Schaer, MD
* Section of Cardiology, Rush-Presbyterian–St. Luke’s Medical Center, 1021 Jelke, 1653 W. Congress Parkway, Chicago, Illinois 60612, USA
Falmeda{at}aol.com
We read with great interest the study by Ajani et al., "The Outcome of Percutaneous Coronary Intervention in Patients With In-Stent Restenosis Who Failed Intracoronary Radiation Therapy" (1). Limited data are available on the outcomes of patients with in-stent restenosis (ISR) who undergo treatment using intracoronary radiation therapy (IRT) and subsequently "fail," and the study by Ajani and colleagues provides new data on this important subject. The investigators reported that the rate of failed IRT was 29%. This is similar to findings from our institution where we reported a 15.6% failure rate after IRT for ISR in a broad range of patients (2). In our study, ostial location and smaller postprocedural minimal luminal diameter were correlated with subsequent failure after IRT. Do the investigators of this current study have information regarding the effects of these factors on influencing long-term clinical outcomes in their patient cohort?
In this current study, cutting balloon angioplasty (CBA) was utilized in only 2% of cases after failed IRT. Because of the potential for minimizing arterial injury, reducing the proliferative neointimal response, achieving a greater postprocedural minimal luminal diameter, and decreasing slippage due to "watermelon seeding," CBA has been shown to be a safe and feasible strategy for the treatment of ISR (3); however, the impact of CBA in combination with IRT for the treatment of ISR has not been well established. We recently reported data from our institution which showed that the strategy of CBA and IRT using Sr-90 for ISR was associated with similar major adverse cardiac events (death, myocardial infarction, and target vessel revascularization) at 6 months compared to percutaneous transluminal coronary angioplasty (PTCA) and IRT in 102 consecutive patients (20.0% vs. 29.8%, p = 0.36) (4). Thus, although CBA has the potential of avoiding geographic miss by limiting the mismatch between the injured and irradiated arterial segments, it does not appear to offer any clinical advantage over conventional balloon angioplasty in combination with IRT, although further studies are needed to clarify this issue. The mechanism behind this observed lack of benefit for the treatment of ISR may be that, although CBA appears to increase neointimal tissue extrusion, intravascular ultrasound studies have shown that CBA, unlike PTCA, is associated with minimal stent overexpansion (5).
The majority of the patients in the current study presented with a focal pattern of restenosis. Did the clinical presentation of these patients differ from those who presented with diffuse or edge restenosis?
In the study by Ajani et al. (1), the mean time to first target vessel revascularization (TVR) was 173 ± 127 days after the index procedure. Other studies have noted that in patients who "fail" IRT, treatment with brachytherapy delays the time to the first TVR (295 ± 206 days) compared to the placebo group (202 ± 167 days) (p = 0.03) (6). Preliminary data from our medical center suggests that up to 25% of patients who ultimately "fail" IRT present more than eight months after the index treatment, and in these patients the mean duration to TVR was 14.2 ± 3.7 months (7). Do the investigators of the current study (1) have data on patients who failed IRT and who presented beyond the traditional time period for restenosis (six to nine months)?
Although glycoprotein IIb/IIIa inhibitors (GPI) have been shown to be beneficial in a wide variety of coronary interventional procedures, the impact of these agents on improving outcomes in patients with ISR using IRT is not clearly defined. One study showed that the utilization of GPI in conjunction with IRT for ISR was associated with similar death, myocardial infarction, and TVR compared to IRT without GPI (19.5% vs. 23.7%, p = 0.511) (8). What was the rate of utilization of GPI in the current study, and did this influence the outcome?
The study by Ajani and co-workers contributes greatly to our understanding of the issues surrounding the optimal implementation of IRT in this high-risk population. Assessing the risk for IRT failure and elucidating the mechanisms underlying these adverse events will contribute significantly to the application of IRT for ISR in the drug-eluting stent era.
 |
References
|
|---|
1. Ajani AE, Waksman R, Cheneau E, et al. The outcome of percutaneous coronary intervention in patients with in-stent restenosis who failed intracoronary radiation therapy. J Am Coll Cardiol. 2003;41:551–556[Abstract/Free Full Text]
2. Almeda FQ, Chua DY, Nathan S, et al. Correlates of failure following treatment with Sr-90 beta irradiation for in-stent restenosis. Catheter Cardiovasc Interv. 2003. In press
3. Almeda FQ, Klein LW. Cutting balloon angioplasty: to cut is to cure? J Invasive Cardiol. 2002;14:725–727[Medline]
4. Almeda FQ, Chua DY, Nathan S, et al. Clinical outcomes of the patients treated with the cutting balloon and Sr-90 beta-irradiation for in-stent restenosis. Cardiovasc Radiat Med. 2002;3:12–15[CrossRef][Medline]
5. Ahmed JM, Mintz GS, Castagna M, et al. Intravascular ultrasound assessment of the mechanism of lumen enlargement during cutting balloon angioplasty treatment of in-stent restenosis. Am J Cardiol. 2001;88:1032–1034[CrossRef][Medline]
6. Prpic R, Teirstein PS, Reilly JP, et al. Long-term outcome of patients treated with repeat percutaneous coronary intervention after failure of gamma-brachytherapy for the treatment of in-stent restenosis. Circulation. 2002;106:2340–2345[Abstract/Free Full Text]
7. Chua DY, Almeda FQ, Senter S, et al. Predictors of late cardiac events following treatment with Sr-90 beta irradiation for instent restenosis (abstr). Cardiovasc Radiat Med 2003. In press
8. Almeda FQ, Chua DY, Senter S, et al. Clinical outcomes of patients treated with and without glycoprotein IIb/IIIa inhibitors and Sr-90 beta irradiation for in-stent restensis (abstr). Presented at the Society of Cardiac Angiography and Intervention 26th Annual Scientific Sessions, Boston, MA, May 2003
|
Top
References