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| Journal of the New Zealand Medical Association,
22-September-2006, Vol 119 No 1242
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Osteosarcoma in New Zealand: an outcome study comparing
survival rates between 1981–1987 and 1994–1999
Hamish Curry, Geoffrey Horne, Peter Devane, Helen
Tobin
Osteosarcoma is the most common non haemopoietic primary
tumour of bone. The estimated incidence is approximately 4–5 per million,
occurring most commonly in the second decade of life (ages 11–20).1
The most recent WHO Classification of Tumours defines eight
different types of osteosarcoma:1conventional
osteosarcoma which is further delineated into three subtypes depending on
the predominant matrix present—osteoblastic (50%), fibroblastic (25%), and
chondroblastic (25%); telangectatic, small
cell, low grade central, parosteal, periosteal, high grade surface, and
secondary osteosarcoma.
The treatment of osteosarcoma is changing as the knowledge
of chemotherapy advances, and surgical techniques and prosthetics improve. The
treatment commonly involves pre- and post-surgical chemotherapy in combination
with surgery (either limb salvage or amputation).
In this study, we wanted to compare the data on patients
with osteosarcoma treated in New Zealand from 1994–1999 to data collected
from a similar study of a cohort from 1981–1987, and then assess if there
had been an improvement in 5-year outcomes.3
In particular, we wanted to assess if a more specific
histological classification had lead to improved outcomes being reported in
certain groups
MethodData was collected from the Cancer Registry at the
Ministry of Health. From 1994, reporting of documented cancers became a legal
requirement; data was collected from 1994 until July 1999. The raw data from
1981–1987 was also retrieved and analysed for comparison.
Information was gathered on patient age at diagnosis,
age at death, sex, tumour site, histological classification, and treatment type.
The coding of information and classification systems used by the Cancer Registry
had not changed between the two cohorts and this was used to enable comparison.
The overall 5-year outcome was collated.
Parosteal and periosteal osteosarcomas were excluded
because of their different behaviour and better outcome.1 In addition,
osteosarcoma of the skull, facial bones, and mandible were excluded (as they are
not treated by orthopaedic surgeons) as well as soft tissue osteosarcomas and
osteosarcomas of an unknown site.
Statistical analysis was performed on the 5-year
outcome results using the Fisher’s exact test to analyse whether a
statistically significant improvement had occurred. Patients with Paget’s
osteosarcoma were excluded from this analysis.
Results1981—1987 dataOf the original 104 cases in the 1981–87 study period,
4 skull osteosarcomas, 1 mandibular osteosarcoma, 1 soft tissue osteosarcoma, 1
osteosarcoma from an unknown site, and 1 sarcoma not specified were excluded,
thus leaving 96 cases of osteosarcoma (61 males and 35 females).
The age distribution of the cases is typical; it shows a
peak in the second decade of life and a further smaller peak in the seventh and
eighth decades (Figure 1).
Figure 1. Age distribution of New Zealand osteosarcoma
cases
 As shown in Figure 2, there were 76
tumours in the appendicular skeleton and 20 in the axial skeleton.
There were 89 cases of osteosarcoma which were not specified
histologically. Four osteosarcomas originated from Paget’s disease, and 3
were telangectactic osteosarcomas.
Staging was documented at the time of diagnosis. Of the 98
cases, 66 were tumours were intracompartmental. There were 11 cases where the
tumour was extracompartmental and 17 cases had metastases. The staging was not
specified in 4 cases.
Treatment consisted of combinations of chemotherapy, surgery
and radiotherapy. No specific data was available for the type of surgery
performed or the chemotherapy regime used.
1994–1999 dataIn the 1994–1999 study period there were 97 registered
cases of osteosarcoma. Of the original cohort, 6 mandibular osteosarcomas, 2
maxillofacial osteosarcomas, 1 abdominal osteosarcoma, and 1 soft tissue
osteosarcoma were excluded. In addition, 3 cases were excluded because the
diagnosis was made at autopsy. Thus 84 cases remained (46 males and 38 females).
A similar bimodal age distribution to the 1981–1987 cohort was found
(Figure 1).
There were 73 tumours in the appendicular skeleton and 11
tumours in the axial skeleton (Figure 2). Histologically, there were 67 cases of
osteosarcoma not otherwise specified; 6 cases were chondroblastic osteosarcoma,
5 were fibroblastic osteosarcoma. Four osteosarcomas originated from
Paget’s disease and there were 2 telangectactic osteosarcomas.
The tumour was intracompartmental in 22 cases while 8 cases
were extracompartmental and 23 cases had metastases. The staging was not
specified in 31 cases.
The modality of treatment of cases in the 1994–1999
cohort was similar to the 1981–1987 cohort. No specific data was available
on the type of surgery performed or the chemotherapy used. Compared to the
1981–1987 cohort, many more patients had chemotherapy combined with
surgery plus there was a significant reduction in the use of radiotherapy (Table
1).
Table 1. Treatment modality comparison between
1981–87 and 1994–99 cohorts
OutcomeAll patient groups demonstrated an improved outcome in the
later cohort, except those with metastatic disease.
Patients with axial tumours had a poorer outcome when
compared to those with appendicular tumours. However both those with axial
tumours and those with appendicular tumours showed an improvement in outcome in
the later cohort.
There were twice as many pelvic osteosarcomas in the earlier
cohort which may partially account for the improved outcome in the later cohort.
Outcome was also broken down in terms of histological
classification for the later cohort. Cases of osteosarcoma in Paget’s
disease had the poorest 5-year outcome (25%). The group of osteosarcomas not
otherwise specified had a 5-year outcome of 42.3%—this is lower than the
5-year outcome of cases with fibroblastic osteosarcomas (60.0%), chondroblastic
osteosarcomas (50.0%), and telangectactic osteosarcomas (50.0%).
Statistical analysisUsing Fisher’s exact test, the improvement in 5-year
outcome between age groups within the cohorts reached statistical significance
in only in those patients older than 40 years (Table 2).
Table 2. Outcome statistics
*Cases of Paget’s
osteosarcoma excluded; †Unspecified staging not included;
‡Probability that the difference in 5-year outcome is
significant.
DiscussionThe most important finding in this study was the improved
5-year outcomes for patients presenting in New Zealand with osteosarcoma. This
improvement was seen throughout most age ranges and stages at presentation but
did not reach statistical significance, except in those patients older than 40
years
The outcome of osteosarcoma continues to improve with better
treatment. Kotz et al have demonstrated an improvement in survival rates in
primary osteosarcoma from 24% in 1965 to 62% in 1994.2 Despite ongoing
developments in the field of chemotherapy and surgery, the overall survival
rates of 55–70% have not changed significantly in the last 15 years,
however.4
One of the aims of this study was to assess if histological
classification had any effect on the outcome. This was not possible due to the
small numbers of specific histological subtypes. No comparison could be made
between the two cohorts, as the classification had changed in the intervening
period to become more specific. The review of subtypes found a poorer outcome of
osteoblastic osteosarcomas compared to other subtypes. The reason for this is
unclear.
There has been little literature surrounding this topic.
Hauben et al found that (in 570 patients less than 40 years of age) survival was
not affected by histological type.5 Our results of overall outcome in the
1994-1999 cohort are comparable to other studies.
For patients aged less than 40 years with a primary
osteosarcoma of an extremity, the 5-year survival rates range from 55–71%
in prospective trials.6–9 Our results compare favourably (60% for similar
patients).
Older patients (>40 years) with osteosarcoma generally do
not survive as long as younger patients. Our 5-year survival results for older
patients are lower than those in other studies in the literature where a 5-year
survival rate of 41.6% is quoted in one study.10
Patients with metastatic disease also have poorer outcomes.
In two studies, the 5-year survival was 24% and 29%, respectively.11,12 Again,
this rate is higher compared to our results.
Caution is necessary when comparing our outcome results with
other studies, as the patient inclusion criteria in those studies are often very
specific and they have higher numbers of cases. Specifically, the numbers of
patients older than 40 years and those with metastatic disease are much smaller
in the New Zealand cohorts, which makes comparison difficult.
Indeed, the main limitation of this study is its small
number of cases. Furthermore, incomplete data was available on the staging of
these tumours, histological grade, and on the presence of skip lesions which
thus made comparisons difficult.
We also acknowledge that more accurate results could have
been obtained if more defined data about histological grade, staging, and
treatment regimes were available.
Despite these reservations, we have shown a trend toward an
improved outcome of patients with osteosarcoma treated in New Zealand which is
similar to reports in the literature from other countries.
Author information:
Hamish Curry, Orthopaedic Registrar, Christchurch Hospital, Christchurch;
Geoffrey Horne, Professor of Orthopaedics, Wellington Hospital, Wellington;
Peter Devane, Orthopaedic Surgeon, Wellington Hospital, Wellington; Helen Tobin,
Orthopaedic Surgeon, Hutt Hospital, Lower Hutt
Acknowledgement: We
thank Gordon Purdie (Wellington School of Medicine) for the statistical
analyses.
Correspondence:
Hamish Curry, Orthopaedic Registrar, c/- Christchurch Hospital, Private Bag
4700, Christchurch. Email: hamishcurry@gmail.com
References:
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