Abstract:
Abstract # 800040
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2003-11-04T21:21:00Z
2003-11-14T15:54:00Z
2003-11-14T15:54:00Z
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Purpose: To determine whether combined radiation therapy
(XRT) and radiofrequency (RF) ablation increases endpoint survival over XRT or
RF ablation alone in a animal tumor model.
Materials and Methods: R3230 mammary adenocarcinoma (1.0 –
1.5 cm) was implanted subcutaneously in 36 female Fischer 344 rats. Tumors were
randomized into four experimental groups: (a) conventional monopolar RF (70° C
for 5 minutes) alone (n=8), (b) RF ablation followed by 20Gy external beam
radiation (1Gray per minute) within 2 hours (n=10) (c) single dose 20Gy
radiation alone (n=8), and (d) no treatment (n=10). The time when the tumor
reached 3.0 cm in diameter (survival endpoint) was recorded. The effect of
treatments on endpoint survival was analyzed by means of analysis of variance
statistics.
Results: Of the animals treated with combined FR and XRT,
local control, manifest by complete resolution of the tumor, was achieved in 9
of 10 (90%) animals. This was significantly greater than the local control
obtained in the RF alone group (1 of 8, 12.5%) (p<0.01). No local tumor
control was seen in the control group of XRT alone group. Endpoint survival was
greatest for the combined treatment group at 55 ± 17 days. Additionally, all
three animals who died prior to 60 days succumbed to metastatic disease of the
lung. Significantly lower survival was achieved for XRT alone (39.5 ± 14 days),
RF alone (30.6 ± 15 days), and the control group (13.6 ± 6 days) (all p<
0.01 compared to combined therapy).
Conclusions: The addition of single high dose radiation as
an adjuvant to RF ablation dramatically improves outcomes. Local cure of
subcutaneous mammary tumors can be achieved, and increased survival compared to
either RF or XRT alone has been observed. Further parametric and optimization
study of this paradigm is warranted in anticipation of potential introduction
of this synergy into the clinic.
Horkan MD, C,
Hot Topic: RF Tumor Ablation: Reduced Tumor Growth with Adjuvant External Beam Radiation in a Rat Breast Tumor Model. Radiological Society of North America 2003 Scientific Assembly and Annual Meeting, November 30 - December 5, 2003 ,Chicago IL.
http://archive.rsna.org/2003/3800040.html