Influence of tumor cell proliferation and sex-hormone receptors on effectiveness of radiation therapy for dogs with incompletely resected meningiomas.
OBJECTIVE
To assess the influence of tumor cell proliferation and sex-hormone receptors on the efficacy of megavoltage irradiation for dogs with incompletely resected meningiomas.


METHODS
Longitudinal clinical trial.


METHODS
20 dogs with incompletely resected intracranial meningiomas.


METHODS
Dogs were treated with 48 Gy of radiation administered 3 times per week on an alternate-day schedule of 4 Gy/fraction for 4 weeks, using bilateral parallel-opposed fields.


RESULTS
Tumor proliferative fraction measured by immunohistochemical detection of proliferating cell nuclear antigen (PFPCNA index) ranged from 10 to 42% (median, 24%). Progesterone receptor immunoreactivity was detected in 70% of tumors. Estrogen receptor immunoreactivity was not detected. An inverse correlation was found between detection of progesterone receptors and the PFPCNA index. The overall 2-year progression-free survival (PFS) rate was 68%. The only prognostic factor that significantly affected PFS rate was the PFPCNA index. The 2-year PFS was 42% for tumors with a high PFPCNA index (value > or = 24%) and 91% for tumors with a low PFPCNA index (value < 24%). Tumors with a high PFPCNA index were 9.1 times as likely to recur as were tumors with a low PFPCNA index.


CONCLUSIONS
This study confirms the value of irradiation for dogs with incompletely resected meningiomas. Prognostic value of the PFPCNA index suggests-that duration of treatment and interval from surgery to start of irradiation may affect outcome. Loss of progesterone receptors in some tumors may be responsible for an increase in PFPCNA index and may indirectly affect prognosis after radiation therapy.
Théon
A P
AP
Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis 95616, USA.
Lecouteur
R A
RA
Carr
E A
EA
Griffey
S M
SM
D000818:Animals; D002455:Cell Division; D018572:Disease-Free Survival; D004283:Dog Diseases / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D004285:Dogs; D005260:Female; D007150:Immunohistochemistry; D008137:Longitudinal Studies; D008297:Male; D008577:Meningeal Neoplasms / Q000473:pathology / Q000532:radiotherapy / Q000662:veterinary*; D008579:Meningioma / Q000473:pathology / Q000532:radiotherapy / Q000662:veterinary*; D011379:Prognosis; D018809:Proliferating Cell Nuclear Antigen / Q000032:analysis*; D018714:Radiotherapy, Adjuvant; D011960:Receptors, Estrogen / Q000032:analysis*; D011980:Receptors, Progesterone / Q000032:analysis*
D018809:Proliferating Cell Nuclear Antigen; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone