N. Fukunagajohnson et al., PATTERNS OF FAILURE FOLLOWING TREATMENT FOR MEDULLOBLASTOMA - IS IT NECESSARY TO TREAT THE ENTIRE POSTERIOR-FOSSA, International journal of radiation oncology, biology, physics, 42(1), 1998, pp. 143-146
Citations number
8
Categorie Soggetti
Oncology,"Radiology,Nuclear Medicine & Medical Imaging
Purpose: Craniospinal radiation (CSRT) followed by a boost to the enti
re posterior fossa (PF) is standard postoperative therapy for patients
with medulloblastoma. A large proportion of recurrences after treatme
nt are local, with approximately 50-70% of recurrences occurring in th
e PF. It is unclear, however, whether these failures are occurring in
the original tumor bed or outside the tumor bed, but still within the
PF. With improved diagnostic imaging, better definition of tumor volum
es, and the use of three-dimensional conformal therapy (3D CRT), we ma
y be able to restrict the boost volume to the tumor bed plus a margin
without compromising local control. This retrospective study analyzes
the patterns of failure within the PF in a series of patients treated
with radiation therapy (RT). Methods: From July 1986 through February
1996, 114 patients >18 months and <18 years with medulloblastoma were
treated at the University of Michigan and Children's Hospital of Phila
delphia, with RT following surgical resection. Of 114, 27 (24%) were f
ound to have a recurrence and form the basis for this study. RT consis
ted of CSRT followed by a boost to the entire posterior fossa. Some pa
tients received adjuvant chemotherapy. Patient's preoperative magnetic
resonance imaging (MRI) and/or computerized tomagraphy (CT) studies w
ere used to compare the original tumor volume with the specific region
of local relapse. Failure was defined as MRI or CT evidence of recurr
ence or positive cerebrospinal fluid cytology. Relapse was scored as l
ocal, if it was within the original tumor bed, and regional if it was
outside of the tumor bed but still within the PF. Results: The median
age of the 27 patients who relapsed was 8.6 years. Three patients were
<3 years old. Of 27, 21 had disease localized to the PF. Of 26, 22 pa
tients received chemotherapy during their treatment regimen; 1 patient
did not have information on systemic treatment. The median dose of RT
to the craniospinal axis was 32.5 Gy and to the PF was 55.2 Gy. The m
edian time to recurrence was 19.5 months. Local failure within the tum
or bed as any component of first failure occurred in 52% (14 of 27) of
all failures, but as the solitary site of first failure in only 2 of
27 failures. Of 14 patients who failed in the tumor bed, II also faile
d in the spine, 8 of 14 also failed within the PF but outside the tumo
r bed, and 7 of 14 failed in all three locations. Local failure within
the PF but outside the tumor bed as any component of first failure oc
curred in 41% (11 of 27) of all failures, but as the solitary site of
first failure in only 1 of 27 failures. Of II patients who failed in t
he PF but outside the tumor bed, 9 also failed in the spine, 8 also fa
iled within the tumor bed, and 7 failed in the all three locations. Of
the failures outside the tumor bed but still within the PF, 7 of II f
ailed in the leptomeninges, 1 in the brainstem parenchyma, and 3 in th
e PF parenchyma. Of 7 who failed in the PF leptomeninges, 6 also faile
d within the spine. Failure within the spine as any component of first
failure occurred in 70% (19 of 27) of all failures and as the only si
te of first failure in 5 of 27 patients. Of 19 patients who failed in
the spine, 11 also failed in the tumor bed, 9 also failed within the P
P but outside the tumor bed, and 9 failed in the all three locations.
Conclusions: Leptomeningeal failure is a common component of failure a
nd occurs in the leptomeninges of the PF, as well as the spine, Isolat
ed tumor bed failure is a rarely observed event and occurred in only 2
of 27 failures described here, Similarly, parenchymal (nonleptomening
eal) failures in the PF but outside of the tumor bed were rare: 4 pati
ents recurred in this manner, only 1 of whom was an isolated event wit
hout other sites of recurrence. Our data suggest that, when the entire
PF is treated, very few failures develop in isolation in the PF outsi
de the tumor bed. Further studies will be necessary to determine if RT
to the tumor bed alone will suffice as opposed to a boost to the enti
re PF. The former approach, using 3D CRT, may minimize ototoxicity and
other morbidity associated with full PF irradiation. (C) 1998 Elsevie
r Science Inc.