Braun et al. BMC Cancer 2011, 11:353 http://www.biomedcentral.com/1471-2407/11/353 adjustment of covariates needs to be achieved. Finally, our finding on global function should be interpreted with caution because the global function score likely reflects the contribution of the physical function score. We also found that physical function, nausea/vomit- ing, insomnia, and diarrhea in newly diagnosed patients predicted survival in multivariate analysis. Similarly, in previously treated patients, physical function was predic- tive of survival in multivariate analysis. For both of these clinical settings, it is easy to appreciate the nega- tive impact these attributes would exert on the ability of a patient to function. While the current study does not elucidate causative relationships between these functions and patient survival, the importance of measuring these functions in patients and attempting to address their effects therapeutically should be obvious. The finding of poorer physical, role and social functioning scores and fatigue, nausea/vomiting, pain, dyspnea and appetite loss symptom scores in previously treated patients as com- pared to newly diagnosed patients is not surprising given that previously treated patients have more advanced disease and are well into their course of illness as compared to newly diagnosed patients. The results of this study have important implications for both clinical and research practices in an integrative oncologic care setting. They suggest that health care professionals should evaluate baseline QoL in all patients and take this into consideration when planning treatment. QoL should also be assessed regularly during treatment and appropriate intervention taken to improve QoL when indicated. QoL was initially designed to be used as a clinical indicator. Self-reported QoL assess- ment using validated questionnaires plays a very impor- tant role in acquiring and monitoring information on patient’s functional and symptom status throughout the course of treatment. In the absence of concrete informa- tion on the prognostic role of QoL in cancer survival, its utility as a clinical indicator should not be jeopardized. In fact, information about QoL in lung cancer patients undergoing treatment can provide healthcare providers with a perspective on post-treatment recovery, including the positive aspects of long-term care, as well as antici- pated problems [3]. Although this study presents interesting findings and additional questions for further inquiry, several limita- tions require acknowledgment. Our study, because of its retrospective nature, relies on data not primarily meant for research. As a result, we could not control for some additional factors in our analyses that could influence survival such as medical comorbidities, performance sta- tus, socioeconomic factors, support system, exercise, insurance coverage, employment and educational level. It has been suggested that QoL data might be markers of the socioeconomic status of cancer patients. For Page 7 of 9 instance, cancer patients with higher social class would have a better QoL, and consequently those who report a better QoL at baseline assessment may live longer [28]. As suggested by Fielding and Wong, full adjustment is needed for factors affecting outcome in order to demon- strate any independent predictive power of QoL [39]. The patient cohort was limited only to those patients who were English speakers and therefore is not repre- sentative of the complete spectrum of lung cancer patients. A majority of our patients had advanced stage disease at presentation. As a result, generalizability of the study findings to NSCLC patients with early stage disease might be questionable. However, we have no reasons to believe that patients with early stage disease will have different findings. Moreover, this study is not able to reveal causative relationships between any QoL element and patient survival. Rather, QoL was found to act as a surrogate marker for otherwise undetected prognostic factors [11]. We did not control for the mul- tiple comparisons made in this study, but this is accep- table for hypothesis-generating studies [26]. Finally, we did not evaluate the prognostic significance of changes in QoL scores during the entire duration of treatment. Nevertheless, this study also has several strengths, including a large sample size; complete data for all QLQ-C30 subscales for the entire study sample; high compliance with completion of the questionnaire; the use of a valid and reliable QoL instrument; comprehen- sive documented clinical parameters in nearly all patients; and availability of mature and reliable survival data. Conclusions This study suggests that baseline global QoL and physi- cal function scale provide useful prognostic information in non-small cell lung cancer patients. Acknowledgements This study was funded by Cancer Treatment Centers of America. We thank Norine Oplt and Carol Wages for providing us with reliable and updated survival data. Authors’ contributions DPB and DG participated in concept, design, data collection, data analysis, data interpretation and writing. EDG participated in concept, design and data interpretation. All authors read and approved the final manuscript. Competing interests The authors declare that they have no competing interests. Received: 27 October 2010 Accepted: 15 August 2011 Published: 15 August 2011 References 1. Jemal A, Siegel R, Ward E, Hao Y, Xu J, Thun MJ: Cancer statistics, 2009. CA Cancer J Clin 2009, 59:225-249. 2. Tishelman C, Lovgren M, Broberger E, Hamberg K, Sprangers MA: Are the most distressing concerns of patients with inoperable lung cancer