W. Zhang
In Regard to Parikh et al
editor purpose comment call attention misleading aspects recently published study relationship radiation therapy rt use within combinedmodality treatment overall survival os stage ii hodgkins lymphoma associated work parikh et al 1parikh rr grossbard ml harrison lb et alearlystage classic hodgkin lymphoma utilization radiation therapy impact overall survivalint j radiat oncol biol phys 2015 93 684693abstract full text full text pdf pubmed scopus 29 google scholar observational study based national cancer database authors use suggestive language imply reported association rt use greater os causal nature unfortunately analysis conducted suffers numerous unacknowledged biases attempts construct survival models depart accepted statistical practice uniform unqualified endorsement radiation therapy implied furthermore reproducible finding reanalysis publicly available dataset using better methodology authors mistakes began failure conduct careful exploratory data analysis would shown heterogeneity effect rt os across comorbidity strata seen significant interaction effect p05 indicators rt use elevated charlson score cox model fit national cancer database data source single hazard ratio reported article favor rt thus inappropriate suitability chosen proportional hazards model questionable traditional log minus log diagnostic plot applied fit model shows nonparallel lines indicative violations models assumptions appropriate model data would account differences early late period effects data issues clustering patients institution also unrecognized unaccounted additional errors made study regard selection biases presented propensity score adjusted analysis defined treatment according treatment received baseline covariates included propensity score adjustment postbaseline events including toxicities progressions deaths withdrawals consent health complications influencing delivery treatment accounted would expected cause bias favor rt presented intention treat analysis similarly flawed accounting baseline factors would bias favor rt better analysis might applied propensity score adjustment intention treat cohort however would still imperfect owing lack data important confounders performance status english proficiency social support health care literacy careful sensitivity analyses would needed place bounds remaining biases influences unmeasured confounders concerns unacknowledged unaddressed troubling none listed authors seem appropriate credentials statistics andor credentialed statistician listed responsibility analyses interpretation literature authors reference seems misread taken context cited work rubin 2rubin db estimating causal effects large data sets using propensity scoresann intern med 1997 127 757763crossref pubmed google scholar propensity score methods meant explain popularize use propensity score techniques justify forcefitting models data without adequate exploratory data analysis full model checking thorough consideration sources bias unfortunately article represents lost opportunity investigate highly important clinical question readership regard claims due skepticism expert analysis published earlystage classic hodgkin lymphoma utilization radiation therapy impact overall survivalinternational journal radiation oncology biology physicsvol 93issue 3previewto examine association radiation therapy rt utilization overall survival os patients earlystage hodgkin lymphoma hl fulltext pdf reply zhanginternational journal radiation oncology biology physicsvol 99issue 2previewto editor appreciate opportunity respond commentary regarding article 1 2 fulltext pdf