Radiosurgery for brain metastasis: impact of CTV on local control.
OBJECTIVE
The purpose of the present analysis was to assess whether adding a 1 mm margin to the gross tumour volume (GTV) improves the control rate of brain metastasis treated with radiosurgery (RS).


METHODS
All the patients had one or two brain metastases, 30 mm or less in diameter, and only one isocentre was used for RS. There were 23 females and 38 males. The median age was 54 years (34-76). The median Karnofsky performance status was 80 (60-100). At the time of RS, 23 patients had no evidence of extracranial disease and 38 had a progressive systemic disease. Thirty-eight patients were treated up-front with only RS. Twenty-three patients were treated for relapse or progression more than 2 months after whole brain radiotherapy. From January 1994 to July 1995, clinical target volume (CTV) was equal to GTV without any margin (33 metastases). From August 1995 to August 2000, CTV was defined as GTV plus a 1 mm margin (45 metastases). A dose of 20Gy was prescribed to the isocentre and 14Gy at the margin of CTV.


RESULTS
The median follow-up was 10.5 months (1-45). The mean minimum dose delivered to GTV was 14.6Gy in the group without a margin and 16.8Gy in the group with a 1 mm margin (P<0.0001). The response of 11 metastases was never assessed because patients died before the first follow-up. Ten metastases recurred, eight in the group treated without a margin and two in the group treated with a 1 mm margin (P=0.01). Two-year local control rates were 50.7+/-12.7% and 89.7+/-7.4% (P=0.008), respectively. Univariate analysis showed that the treatment group (P=0.008) and the tumour volume (P=0.009) were prognostic factors for local control. In multivariate analysis, only the treatment group with a 1 mm margin was an independent prognostic factor for local control (P=0.04, RR: 5.8, 95% CI [1.08-31.13]). There were no significant differences, either in overall survival rate or in early and late side effects, between the two groups.


CONCLUSIONS
Adding a 1 mm margin to the GTV in patients treated with RS significantly improves the probability of metastasis control without increasing the side effects.
Noël
Georges
G
Department of Radiation Oncology, Groupe Pitié-Salpêtrière, Assistance Publique-Hôpitaux de Paris, 47-83, Bd de l'Hôpital, 75651 Cedex 13, Paris, France.
Simon
Jean Marc
JM
Valery
Charles Ambroise
CA
Cornu
Philippe
P
Boisserie
Gilbert
G
Hasboun
Dominique
D
Ledu
Dominique
D
Tep
Bernadette
B
Delattre
Jean Yves
JY
Marsault
Claude
C
Baillet
François
F
Mazeron
Jean Jacques
JJ
D000230:Adenocarcinoma / Q000473:pathology / Q000556:secondary* / Q000601:surgery*; D000328:Adult; D000368:Aged; D001932:Brain Neoplasms / Q000473:pathology / Q000556:secondary* / Q000601:surgery*; D016371:Cranial Irradiation; D018572:Disease-Free Survival; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016634:Radiosurgery / Q000379:methods*