Cancer Causes Control (2014) 25:407–408 DOI 10.1007/s10552-014-0342-1
LETTER TO THE EDITOR
Reply to comments by Dr. Frisch and Dr. Van Howe Manit Arya • Ruoran Li • Asif Muneer Michel P. Coleman
•
Received: 19 December 2013 / Accepted: 8 January 2014 / Published online: 17 January 2014 Ó Springer International Publishing Switzerland 2014
Dear editor, We appreciate the opportunity to respond to the thoughtful comments by Dr. Frisch and Dr. Van Howe. They suggest the need for a trend test to determine whether the changes in age-standardized rates are statistically significant. We used variance-weighted least squares linear regression to estimate the average year-onyear change in the incidence rate per 100,000 men per year between 1979 and 2009. The average annual increase in the incidence rate is numerically small at 0.007 (95 % CI 0.005–0.010) per 100,000 per year, but it is statistically significant (p \ 0.001). This modeled trend represents an absolute increase in the age-standardized incidence rate of 0.22 per 100,000, or about a 20 % increase over the 31-year period 1979–2009. Frisch and Van Howe recommend examination of trends in the age-specific incidence rates by calendar period and by birth cohort (both in 10-year age intervals). The trend in incidence rates in England over the 30-year period 1980–2009 varied with age (Fig. 1; Table 1). For men in the four 10-year age groups 30–69 years at diagnosis, the mean absolute increase in incidence every five years was between 0.03 and 0.17—these increases are again small
M. Arya (&) A. Muneer Department of Urology, University College Hospital, London, UK e-mail: [email protected] M. Arya Barts Cancer Institute, Queen Mary University of London, London, UK R. Li M. P. Coleman Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, Keppel Street, London, UK
numerically, but all are statistically significant at the 5 % level. The increases ranged between 28 and 59 % over the 30-year period; in other words, the age-specific rates rose by about 1–2 % per year. The linear regression models fitted the data well, and there is little evidence of any departure from linear drift, though incidence increased somewhat more markedly among men aged 60–69 years after 2000 (Fig. 1). Incidence fluctuated slightly for men aged 20–29 and 70–79 years, but there was no significant trend. By contrast, among men aged 80 years or over, the incidence rate fell steadily by an average of 0.30 per 100,000 person-years every five years (p value for trend 0.03), corresponding to an overall decrease of 15 % from the incidence rate in 1980–1984. Similar patterns were observed in the age-specific incidence of penile cancer among successive birth cohorts of men born over the 80-year period 1895–1975 (Fig. 2; Table 2). It was only possible to examine change between three successive 10-year birth cohorts in the age-specific incidence rates for 10-year age groups. For men aged 30–69 years, the incidence rates increased significantly between three successive birth cohorts, with an overall increase of 24–44 %. Incidence among men aged 80 years and over fell between three successive birth cohorts born in the early 1900s, but there was no consistent trend for men aged 70–79 years. Frisch and Van Howe suggest we have stated that an increasing incidence of penile cancer could be explained in part by decreasing rates of childhood circumcision. We have in fact specified this may be one of the factors, but in the ‘‘Abstract,’’ we document that these changes may also be explained by changes in sexual practice and greater exposure to sexually transmitted oncogenic human papilloma viruses—this is dealt with in depth in the ‘‘Discussion’’ section of the article.
123
408
Cancer Causes Control (2014) 25:407–408
Fig. 1 Penile cancer: age-specific incidence rates per 100,000 per year (with 95 % confidence intervals, shaded areas), by calendar period 1980–1984 to 2005–2009, England
Fig. 2 Penile cancer: age-specific incidence rates per 100,000 per year (with 95 % confidence intervals, shaded areas), successive 10-year birth cohorts born during 1895–1975, England
Table 1 Average change every five years in the annual incidence rate per 100,000 per year: penile cancer, England, men aged 20 and over diagnosed since 1980–1984
Table 2 Average change in age-specific incidence rate between successive 10-year birth cohorts: penile cancer, England, men diagnosed aged 20 and over and born during 1895–1975
Age group (years)
Annual incidence ratea during 1980–1984
Average change every five yearsb
p value for trend
Overall change (%) in 31 years
Age group (years)
Incidence ratea in the first cohort
Mean change between successive cohortsb
p value
Overall % changec
20–29
0.06
-0.001
0.90
-4
20–29
0.04
0.002
0.61
19
30–39
0.29
0.048
0.03
34
30–39
0.27
0.026
0.01
48
40–49
0.73
0.143
0.00
38
40–49
0.80
0.066
0.00
45
50–59
1.51
0.336
0.00
44
50–59
1.43
0.168
0.00
59
60–69
3.16
0.359
0.00
24
60–69
3.30
0.163
0.00
28
70–79
6.21
-0.120
0.40
-4
70–79 80?
6.31 10.33
-0.063 -0.307
0.35 0.03
-5 -15
10.23
-0.625
0.03
-12
a
Per 100,000 men per year
b
Average absolute change in the incidence rate every five years, from variance-weighted least squares linear regression model
123
80? a
Per 100,000 men per year
b
Mean absolute change in the incidence rate per 100,000 per year between successive 10-year birth cohorts
c
Overall change between three successive birth cohorts
LETTER TO THE EDITOR
Reply to comments by Dr. Frisch and Dr. Van Howe Manit Arya • Ruoran Li • Asif Muneer Michel P. Coleman
•
Received: 19 December 2013 / Accepted: 8 January 2014 / Published online: 17 January 2014 Ó Springer International Publishing Switzerland 2014
Dear editor, We appreciate the opportunity to respond to the thoughtful comments by Dr. Frisch and Dr. Van Howe. They suggest the need for a trend test to determine whether the changes in age-standardized rates are statistically significant. We used variance-weighted least squares linear regression to estimate the average year-onyear change in the incidence rate per 100,000 men per year between 1979 and 2009. The average annual increase in the incidence rate is numerically small at 0.007 (95 % CI 0.005–0.010) per 100,000 per year, but it is statistically significant (p \ 0.001). This modeled trend represents an absolute increase in the age-standardized incidence rate of 0.22 per 100,000, or about a 20 % increase over the 31-year period 1979–2009. Frisch and Van Howe recommend examination of trends in the age-specific incidence rates by calendar period and by birth cohort (both in 10-year age intervals). The trend in incidence rates in England over the 30-year period 1980–2009 varied with age (Fig. 1; Table 1). For men in the four 10-year age groups 30–69 years at diagnosis, the mean absolute increase in incidence every five years was between 0.03 and 0.17—these increases are again small
M. Arya (&) A. Muneer Department of Urology, University College Hospital, London, UK e-mail: [email protected] M. Arya Barts Cancer Institute, Queen Mary University of London, London, UK R. Li M. P. Coleman Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, Keppel Street, London, UK
numerically, but all are statistically significant at the 5 % level. The increases ranged between 28 and 59 % over the 30-year period; in other words, the age-specific rates rose by about 1–2 % per year. The linear regression models fitted the data well, and there is little evidence of any departure from linear drift, though incidence increased somewhat more markedly among men aged 60–69 years after 2000 (Fig. 1). Incidence fluctuated slightly for men aged 20–29 and 70–79 years, but there was no significant trend. By contrast, among men aged 80 years or over, the incidence rate fell steadily by an average of 0.30 per 100,000 person-years every five years (p value for trend 0.03), corresponding to an overall decrease of 15 % from the incidence rate in 1980–1984. Similar patterns were observed in the age-specific incidence of penile cancer among successive birth cohorts of men born over the 80-year period 1895–1975 (Fig. 2; Table 2). It was only possible to examine change between three successive 10-year birth cohorts in the age-specific incidence rates for 10-year age groups. For men aged 30–69 years, the incidence rates increased significantly between three successive birth cohorts, with an overall increase of 24–44 %. Incidence among men aged 80 years and over fell between three successive birth cohorts born in the early 1900s, but there was no consistent trend for men aged 70–79 years. Frisch and Van Howe suggest we have stated that an increasing incidence of penile cancer could be explained in part by decreasing rates of childhood circumcision. We have in fact specified this may be one of the factors, but in the ‘‘Abstract,’’ we document that these changes may also be explained by changes in sexual practice and greater exposure to sexually transmitted oncogenic human papilloma viruses—this is dealt with in depth in the ‘‘Discussion’’ section of the article.
123
408
Cancer Causes Control (2014) 25:407–408
Fig. 1 Penile cancer: age-specific incidence rates per 100,000 per year (with 95 % confidence intervals, shaded areas), by calendar period 1980–1984 to 2005–2009, England
Fig. 2 Penile cancer: age-specific incidence rates per 100,000 per year (with 95 % confidence intervals, shaded areas), successive 10-year birth cohorts born during 1895–1975, England
Table 1 Average change every five years in the annual incidence rate per 100,000 per year: penile cancer, England, men aged 20 and over diagnosed since 1980–1984
Table 2 Average change in age-specific incidence rate between successive 10-year birth cohorts: penile cancer, England, men diagnosed aged 20 and over and born during 1895–1975
Age group (years)
Annual incidence ratea during 1980–1984
Average change every five yearsb
p value for trend
Overall change (%) in 31 years
Age group (years)
Incidence ratea in the first cohort
Mean change between successive cohortsb
p value
Overall % changec
20–29
0.06
-0.001
0.90
-4
20–29
0.04
0.002
0.61
19
30–39
0.29
0.048
0.03
34
30–39
0.27
0.026
0.01
48
40–49
0.73
0.143
0.00
38
40–49
0.80
0.066
0.00
45
50–59
1.51
0.336
0.00
44
50–59
1.43
0.168
0.00
59
60–69
3.16
0.359
0.00
24
60–69
3.30
0.163
0.00
28
70–79
6.21
-0.120
0.40
-4
70–79 80?
6.31 10.33
-0.063 -0.307
0.35 0.03
-5 -15
10.23
-0.625
0.03
-12
a
Per 100,000 men per year
b
Average absolute change in the incidence rate every five years, from variance-weighted least squares linear regression model
123
80? a
Per 100,000 men per year
b
Mean absolute change in the incidence rate per 100,000 per year between successive 10-year birth cohorts
c
Overall change between three successive birth cohorts
