Kidney tumors comprise approximately 6% of all
childhood cancers. WT is the most common primary renal
neoplasm in children. The exact incidence and outcome of
these tumors in Pakistan is unknown. Although our study
is a single institution experience, biases regarding patient
selection have to be considered. In the absence of larger
cohorts this may represent some of our patient characteristics
and help promote better understanding of our population.
In our study the most common histopathological
subtype was WT (91%). The median age at the time of
diagnosis was 4 years, which is slightly higher than reported
from developed countries but similar to the data
reported from Sudan, Nigeria and other developing countries[
2,
6,
10-
13]. Boys outnumbered girls with a ratio of 1.5:1, again consistent with literature from other resource
poor countries[
14-
16]. This may either be a true reflection
of sex predilection for the disease or a gender bias
in our culture where males are brought preferentially to
medical attention than females.
The first Wilms tumor trial from the United Kingdom
Children Cancer Study Group (UKCCSG) reported abdominal
mass as the most common presenting symptom
with comparable reports from other studies[6,13,17,18].
Fever, abdominal pain, gross hematuria, and hypertension
are other frequently seen symptoms in these children[2].
Similar observations were seen in our study population.
A substantial proportion (74%) of our patients presented
as advanced stage disease (Stage III and IV). This is another significant factor that determines the outcome.
Davidson and others[19] have reported a similar pattern
of advanced stage disease in developing countries. In
our study the relapse free survival of children with WT
was 56% that compares with the reported figures from
developing countries but still far less than the developed
countries[4,6,13,20]. Older age and advanced stage of
the disease found in our children at presentation might
have contributed to the poorer outcome. The outcome in
five children is unknown as they were lost to follow-up,
two of them just after completion of therapy and 3 after
relapse. Loss to follow-up and abandonment of treatment
are factors known to contribute to poor survival[8,21].
All relapses seen in our children with WT were seen within
6 months of completion of therapy. Early relapses have
been associated with poor outcome and may reflect more
aggressive nature of disease seen in children residing in
developing countries[22]. The most frequent sites of relapse
reported in children with WT are the lungs, while
original tumor bed, liver, brain and bone are less frequently
involved[23]. In our observation primary tumor bed
was the predominant site of relapse seen in all patients
with combination of lung and/or liver metastasis. The relapses
were seen more in children who had pre-operative
chemotherapy (PC). Under staging because of difficulty
of assessing nodal spread and alteration in histology with
PC has been known to increase local relapses as shown
in SIOP 6 trial[24]. All 5 NWTS trials have been based
on upfront nephrectomy (UN) with risk adapted chemotherapy/
radiotherapy and recommendation that all children
who had inoperable tumors at diagnosis be treated
as Stage III to overcome the above mentioned issues. The
International Society of Pediatric Oncology (SIOP) on the
other hand uses PC to decrease the risk of tumor spillage.
With the excellent outcome of children treated on either
of the two regimens the aim is now to decrease the risk of
potential long term sequelae without altering the efficacy.
Cardiotoxicity secondary to anthracyclines and effects on
growth and fertility after abdominal irradiation are the
major long term sequelae seen in these patients[25].
In our patients advanced disease at diagnosis resulting
in inadequate local control even with delayed nephrectomy,
further delay in radiation because of parental anxiety and concerns, intra-operative tumor spillage and intolerance
to chemotherapy could be some of the risk factors
for relapses in our patients. Multidisciplinary team approach
comprising of surgeons, radiation and pediatric
oncologist with development of expertise in their respective
fields is essential for improving the outcome of these
children. Uniform protocols need to be established to give
standard of care to all and to evaluate the outcome in a
more significant manner. Collaborative efforts also need
to be established between the caregivers and different
centres involved in the care of these children as all facilities
may not be available at a single institute.
In contrast to WT, recurrences in CCSK are usually
seen 3 years after completion of treatment. The most
preferential sites of recurrences are bone and local bed
of tumor followed by brain and liver[26]. The only child
with CCSK diagnosed and treated at our hospital relapsed
after 24 months. Another unusual finding in our study was
a child with RTK who presented at 8 years of age. The
NWTS reported RTK being more frequently seen in children
less than 2 years of age with only one out of 142 children
above 8 years of age[27]. Although the prognosis
is better for older children, our patient died early during
chemotherapy secondary to infection.
A significant proportion (22%) of our children left
after the establishment of diagnosis. The exact reasons
for leaving were not ascertained but inadequate finances,
ignorance, lack of support in terms of lodging and misconceptions
about the disease as reported in other studies,
were the most probable factors[6,7,13,19].
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