Workshop on methods for studying cancer patient survival with application in Stata
This one-day workshop was held on Thursday September 6 in conjunction with the Nordic and Baltic Stata Users Group meeting on Friday September 7.
|Date:||Thursday September 6, 2007|
08:30 AM–09:00 AM
09:00 AM–12:00 PM Morning session
Department of Medical Epidemiology and Biostatistics
Nobels väg 12A
SE-171 77 Stockholm
The aim of the workshop is to discuss and compare approaches to estimating and modeling relative survival (excess mortality) and their application in Stata. The workshop will include presentations from invited speakers who have developed methodology implemented in Stata.
The workshop is aimed at participants who have prior knowledge of methods for population-based cancer survival analysis or have a very strong background in biostatistics and Stata.
|08:30-09:00||Registration and coffee/sandwich|
|09:00-09:15||Paul Dickman: introduction and welcome|
|09:15-09:40||Bernard Rachet: estimating relative survival using the strel command, including period estimation|
|09:45-10:15||Paul Dickman: estimating relative survival using the strs command, including period estimation|
|10:45-11:10||Paul Dickman: modelling excess mortality using step functions|
|11:15-11:40||Bernard Rachet: modelling excess mortality using fractional polynomials and spline functions (on the log hazard scale)|
|13:00-13:30||Chris Nelson: modelling excess mortality using spline functions on the log cumulative hazard scale, the strsrcs command|
|13:30-14:10||Discussion: comparison of different approaches to modelling the baseline hazard (invited discussant: Patrick Royston)|
|14:40-15:25||Paul Lambert: estimating cure models, the strsmix and strsnmix commands|
|15:30-16:15||Ula Nur: modelling relative survival in the presence of incomplete data|
|16:20-17:00||Discussion of Paul and Ula's presentations and directions for future research and development (invited discussant: Patrick Royston)|
|18:30-||Dinner at restaurant två (Rörstrandsgatan 9A)|
The primary focus will be on approaches to modeling excess mortality, particularly when proportional excess hazards are not appropriate. Many of the approaches to modeling differ only in the approach to modeling the baseline hazard. The various approaches will be discussed from both a theoretical and practical approach (i.e., implementation using Stata). All speakers will use standard datasets in their presentations to facilitate comparison of the various approaches. These datasets will be distributed to all participants in advance and Stata code presented during the workshop will be available on this web site. We will discuss proposals for future methodological development and possible collaboration, as well as possibilities for standardizing the Stata commands (at least to the extent it is possible).
About the presenters
Paul Dickman joined the Department of Medicial Epidemiology and Biostatistics at Karolinska Institutet in 1999 where he conducts research in epidemiology and biostatistics with particular focus on cancer epidemiology. He has long been interested in the analysis of cancer patient survival, the topic of his 1997 doctoral thesis where he studied with Professor Timo Hakulinen. His primary interests lie in statistical methods for estimating and modelling relative survival. He has published widely in the field of cancer patient survival, is a coauthor of the Stata strs command for estimating and modelling relative survival, and taught courses in cancer survival analysis in eight different countries.
Paul Lambert is a senior lecturer in Medical Statistics in the Centre for Biostatistics and Genetic Epidemiology, Department of Health Sciences at the University of Leicester. Over the last few years Paul's main research interest has been in developing methods for modelling relative survival. In particular modelling time-dependent covariate effects, incorporating period analysis in statistical models and the estimation and modelling of 'cure' in population-based cancer studies. He has developed methods to use fractional polynomial in relative survival models for both the baseline excess hazard and time-dependent covariate effects (using the mfp command) and has also developed software to fit cure models for relative survival (strsmix and strsnmix). His other interests include the use of Bayesian methods in medical research, evidence synthesis and hierarchical models.
Chris Nelson is a postgraduate student at the University of Leicester. He has extended the flexible parametric model for censored survival data proposed by Royston and Parmar to enable modelling of excess mortality and written the Stata strsrcs for estimating the model using Stata. The model provides smooth estimates of the relative survival and excess mortality rates by using restricted cubic splines on the log cumulative excess hazard scale.
Ula Nur studied for her first degree in Statistics and Computer science at the University of Khartoum, Sudan. She then completed an MSc in Medical Statistics, at the London School of Hygiene and Tropical Medicine. She worked at the Department of Neurosciences and Mental Health, Imperial College London, as a Research Associate in Medical Statistics for three years. For her doctoral thesis she investigated the impact of methods of handling missing data on estimates in cohort studies, with a focus on multiple imputations. She was awarded a PhD in Biostatistics from the University of Leeds in 2004. She joined the Cancer Survival Group as a Lecturer in Cancer Survival in December 2005. Ula’s current research is on geographical and socio-economic inequalities in cancer survival, and modelling relative survival in the presence of incomplete data.
Bernard Rachet is a clinical senior lecturer in cancer epidemiology in the Non-Communicable Disease Epidemiology Unit, Epidemiology and Public Health Department at the London School of Hygiene and Tropical Medicine. Qualified in medicine, he completed an MSc in epidemiology, then a PhD in epidemiology at the International Agency for Research on Cancer (IARC), France. Before joining the London School in 2002, he worked with Professor Jack Siemiatycki in the Epidemiology and Biostatistics Unit of INRS-IAF, Montreal, Canada, for three years. His work mainly focussed on cancer risks associated with occupational and environmental exposures, and on the flexible modelling of complex dose-response relations and time-dependent changes in relative risks. Since 2005, he is co-principal investigator with Professor Michel Coleman in a new five-year C ancer Research UK Programme Grant focussed on cancer survival. With the Cancer Survival Group, he is carrying out a wide range of projects to quantify, describe and explain patterns and trends in cancer survival by socio-economic group, geographic area and ethnicity, as well as extending the methodology and tools for survival analysis. He is also responsible for the development of strel, a STATA program for relative survival analysis He co-organised several courses on cancer survival at the London School.
Dickman PW, Coviello E, Hills M. Estimating and modelling relative survival. Stata Journal 2007 (in press) [Full text in PDF format]
Relevant papers on modelling the baseline hazard using flexible functionsNelson C, Lambert PC, Squire IB, Jones DR. Flexible Parametric Models for Relative Survival, with Application in Coronary Heart Disease. Statistics in Medicine 2007 (in press). [Full text in PDF format]
Relevant papers on cure fraction models in population-based cancer survival analysis
Lambert PC. Modeling of the cure fraction in survival studies. Stata Journal 2007 (in press) [Full text in PDF format]
Lambert PC, Thompson JR, Weston CL, Dickman PW. Estimating and modelling the cure fraction in population-based cancer survival analysis. Biostatistics 2007;8:576-94. [Medline] [Full text in PDF format]
Lambert PC, Dickman PW, Osterlund P, Andersson T, Sankila R, Glimelius B. Temporal trends in the proportion cured for cancer of the colon and rectum: A population-based study using data from the Finnish Cancer Registry. Int J Cancer. 2007 (in press). [Medline] [Full text in PDF format]
Paul Lambert. Models for Estimating "Cure" from Cancer
Patrick Royston. Invited discussion
Stata commands and data files for the workshop
Stata 9 was used during the workshop. The Stata commands, data files, and do files used during the workshop are distributed as two Stata packages, one package for the cure modelling commands and one for all other files. Once installed, the packages can be updated using -adoupdate-. I suggest you create a new directory, set it as the Stata working directory, and issue the following Stata commands.
net install http://www.pauldickman.com/workshop/download/workshop, all
net install http://www.pauldickman.com/workshop/download/cure, all
The strel command can be downloaded here (registration required).
The packages contains the following:
strs (Paul Dickman et al.)
strsrcs (Chris Nelson)
strsmix and strsnmix (Paul Lambert)
ice (Patrick Royston)
mim (JC Galati, P Royston & JB Carlin)
Two data sets kindly provided by the Finnish cancer registry (colon carcinoma and skin melanoma)
Finnish general population mortality rates (popmort.dta)
Life table estimation using strs and save data for modelling
colon_lifetable_strs_period.do (period analysis)
Modelling excess mortality using Poisson regression using a step function for the baseline hazard
Modelling the colon carcinoma data using strsrcs
colon_merge_strsrcs.do - setup dataset
colon_fpm_strsrcs.do - use models to get survival and hazard
colon_ehrr_strsrcs.do - calculate excess hazard rate ratios
colon_continuous_strsrcs.do - use age as continuous
Modelling the colon carcinoma data using cure models
Modelling the colon carcinoma data in the presence of incomplete data
Note: the above do file calls the -ice-, -mim-, and -mvpatterns- packages. -ice- and -mim- are installed with the workshop package. -mvpatterns- can be installed as follows:
net install dm91, from(http://www.stata.com/stb/stb61)
Comparison of various approaches to modelling the colon carcinoma data
These two files were provided by Paul Lambert. The first fits various proportional excess hazards models and compares estimates of the excess hazard ratio and also plots the different estimates of the baseline hazard. The second fits non proportional excess hazards for age group and plots the different estimates of the excess hazard ratio for age group 4. Need to install xpredict.
log excess hazard ratios and standard errors for various PEH models ------------------------------------------------------------------ Variable | strsrcs strsnmix piecewise FP splines ----------+------------------------------------------------------- agegrp2 | 0.0798 0.0760 0.0816 0.0800 0.0797 | 0.0644 0.0645 0.0644 0.0644 0.0644 agegrp3 | 0.2047 0.1979 0.2087 0.2033 0.2029 | 0.0594 0.0595 0.0595 0.0595 0.0595 agegrp4 | 0.5262 0.5154 0.5506 0.5362 0.5350 | 0.0601 0.0602 0.0601 0.0601 0.0601 female | -0.0084 -0.0031 -0.0039 -0.0069 -0.0065 | 0.0258 0.0259 0.0258 0.0257 0.0257 year8594 | -0.1859 -0.1926 -0.1934 -0.1842 -0.1850 | 0.0250 0.0251 0.0250 0.0249 0.0250 ------------------------------------------------------------------ legend: b/se