Relation of clinical success in coronary brachytherapy to dose.
Intravascular brachytherapy is the primary treatment for coronary in-stent restenosis. Variations in dose in the treated artery may represent a potential cause of treatment failure. We compared dose distributions in patients who had developed recurrent restenosis (treatment failure) with those in patients who remained event free at 9 months (treatment success). We followed 140 patients who were receiving brachytherapy for in-stent restenosis with 4 radiation delivery devices to identify treatment failures and successes. Through a nested case-control construct, treatment failures (n = 14) were compared 1:2 with treatment successes (n = 28) matched by radiation delivery system and in-stent restenosis lesion pattern. The dose absorbed by 90% of the artery encompassed by the external elastic membrane (D(90)EEM) was calculated by applying intravascular ultrasound at 2-mm intervals along the treated lesion. Dose calculations were performed using dose kernel integration techniques generated from Monte Carlo simulations. The mean minimum D(90)EEM in treatment failures was 7.46 +/- 1.98 Gy, and that in treatment successes was 8.87 +/- 1.13 Gy (p = 0.007). Using a minimum dose threshold of 8.4 Gy, a minimum D(90)EEM <or=8.4 Gy occurred in 13 patients (93%) whose treatment failed but only in 9 patients (32%) whose treatment was a success (p <or=0.001). No confounding variables were found to be statistically significant between treatment failures and successes. In conclusion, current brachytherapy dose prescriptions allow for inter- and intralesion variations in dose. Arteries that receive <or=8.4 Gy at any point along the external elastic membrane are more likely to result in treatment failures. Dosimetry guided by intravascular ultrasound may be critical to ensure adequate dose delivery and outcomes.
Section of Cardiovascular Medicine, Department of Internal Medicine, Yale School of Medicine and West Haven VA Hospital, New Haven, Connecticut 06510, USA.
Harsimran S
HS
Singh
Ning
N
Yue
Nassir
N
Azimi
Ravinder
R
Nath
Kenneth B
KB
Roberts
Steven
S
Pfau
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001918:Brachytherapy; D016022:Case-Control Studies; D003237:Connecticut; D017023:Coronary Angiography; D023903:Coronary Restenosis / Q000175:diagnosis / Q000532:radiotherapy*; D003331:Coronary Vessels / Q000000981:diagnostic imaging / Q000528:radiation effects; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011879:Radiotherapy Dosage; D012189:Retrospective Studies; D013223:Statistics as Topic; D016896:Treatment Outcome; D018084:Ultrasonography, Interventional