Incidence

2823 Neuro-Oncology cases were diagnosed between 1 January 1987 and 31 December 1996. This sample includes all BC residents diagnosed with either benign disease or malignant tumours during this ten-year period.

Linear regression analysis of the incidence and mortality trends indicates that incidence tends to increase on average by almost 13 cases each year (p-value < 0.001) and mortality increases on average by 4 cases a year (p-value = 0.02). To determine if those trends are only due to the growth and aging of BC population age-standardized incidence and mortality rates were calculated.

These rates are standardized to the age distribution of the 1991 Canadian Population. The plot indicates only a very slight increasing trend of approximately 1 case per 400,000, per year in the incidence (p-value = 0.061) and no increase in mortality.

These rates are standardized to the age distribution of the 1991 Canadian Population. The plot indicates only a very slight increasing trend of approximately 1 case per 400,000 per year in the incidence (p-value = 0.061) and no increase in mortality.

Age

The age of patients diagnosed in BC during these ten years ranges from 0 to 99 years. Three quarters of diagnosed patients were 39 year old and older, median age at diagnosis was 57 years and the mean was 53.1 years. Age distribution is presented on the histogram below:

REFERRAL

The plot shows that the majority (72.3%) of diagnosed cases was referred to BCCA. It also suggests that the number of non-referred cases tends to increase over the ten years. Linear regression analysis indicates that this number increases on average by 9 cases per year (p < 0.001). Such increase is not only due to increase in incidence; relative to the total number of diagnosed cases the percent of non-referred cases increases by about 2 each year (p = 0.001).

Astrocytoma

As indicated in the table of the incidence by diagnosis type astrocytoma has the most frequent diagnosis (57.95% of incidence). Severity of the disease is reflected by its grade.

The plot indicates substantial difference in survival for the four grades of astrocytoma. The estimates for Grade 1 diagnosis are rather unreliable, due to the low number of cases in the sample; the estimated median survival for this grade is longer than 10 years. The median survival for Grade 2 is 4.9 years, 95% confidence interval for this estimate is from 4.1 to 6.7 years. The median survival time for Grade 3 is only 1 year with 95% confidence interval is from 0.9 to 1.3 years. The median survival time for Grade 4 is even shorter: 0.6 year with 95% confidence interval of 0.6 to 0.7 year.