Abstract B15: Second-hand smoke (SHS) and smoking cessation in non-tobacco related cancers
Authors: Eng Lawson , Qiu Xin , Su Jie , Brown M Catherine , Irwin Margaret , Pringle Dan , Naik Hiten , Niu Chongya , Mahler Mary , Hon Henrique , Tiessen Kyoko , Charow Rebecca , Thai Henry , Ho Valerie , Pat Vivien , Herzog Lindsay , Ho Anthea , Jones Jennifer M. , Howell Doris , Goldstein David P. , Giuliani Meredith E. , Xu Wei , Selby Peter , Liu Geoffrey 
Published: October 2015

Abstract
Introduction: Continued smoking after a diagnosis of cancer has been found to lead to poorer treatment response, reduced survival and quality of life and increased risk of second primary cancers. We have previously demonstrated that SHS (exposure at home, with spouses and peers) is a significant barrier to smoking cessation in tobacco-related (lung and head and neck) cancers with adjust odds ratios of 6-9 (PMID: 24419133, 23765604) for quitting 1 year after diagnosis and quitting at any time after diagnosis; relationships stronger than in non-cancer populations. Here, we examined whether this relationship exists in cancers that are not traditionally associated with smoking.
Patients and Methods: Cancer survivors from a single tertiary cancer centre, Princess Margaret Cancer Centre (Toronto, Canada) completed a one-time cross-sectional questionnaire assessing their socio-demographics, functional status, smoking history and SHS exposure. Clinico-pathological variables were obtained through review of patient charts. Multivariate logistic regression and Cox-proportional hazard models evaluated the association of SHS with smoking cessation at 1 year after diagnosis and any time after diagnosis, and time-to-quitting respectively, adjusted for significant co-variates.
Results: A total of 1011 non-tobacco related cancer survivors were surveyed between 2012 and 2014: 19% breast, 15% gastrointestinal, 16% genitourinary, 12% gynecological, 23% hematologic, 15% other. Median follow-up time after diagnosis was 26 months. Among the 162 patients currently smoking at diagnosis, 35% quit 1 year after diagnosis and 48% quit at any time after diagnosis. None of the 306 ex-smokers and 543 never smokers (re-)started smoking after diagnosis. Home exposure to SHS was found to be strongly associated with reduced smoking cessation in cancer patients at any time after diagnosis (aOR=4.28, 95% CI (1.56-11.78), P=4.8E-3), while there was a less strong and non-significant trend for home exposure to SHS and reduced smoking cessation at 1 year after diagnosis (aOR=2.56, 95% CI (0.91-7.22), P=0.08)). Time-to-quitting analysis for home exposure to SHS were consistent with these results (aHR=2.76, 95% CI (1.15-6.59), P=0.02)). Unlike lung and head and neck cancer patients, spousal and peer smoking were not found significantly associated with smoking cessation at either time-point (P&gt;0.05). Kaplan-Meier analysis found that 72% of patients who quit, did so within 1 year of their cancer diagnosis. When comparing factors between patients quitting one year after diagnosis versus quitting more than one year after diagnosis, those quitting at one year were more likely older (P&lt;0.05) and have received surgery as part of their cancer care (P=0.06).
Conclusions: Home exposure to SHS is a significant barrier to quitting smoking after a diagnosis of cancer in both tobacco-related and non-tobacco related cancers; while spousal and peer smoking were not found significantly associated with smoking cessation in non-tobacco related cancers. Unlike in tobacco-related cancers, home exposure to SHS had a weaker association with quitting at 1 year after diagnosis than quitting at any time after diagnosis; suggesting the effect of the “teachable moment” with SHS and cancer may not be as strong in these cancers. Survivorship programs focusing on secondary prevention and smoking cessation in cancer patients should focus on incorporating SHS exposure.
Citation Format: Lawson Eng, Xin Qiu, Jie Su, M Catherine Brown, Margaret Irwin, Dan Pringle, Hiten Naik, Chongya Niu, Mary Mahler, Henrique Hon, Kyoko Tiessen, Rebecca Charow, Henry Thai, Valerie Ho, Vivien Pat, Lindsay Herzog, Anthea Ho, Jennifer M. Jones, Doris Howell, David P. Goldstein, Meredith E. Giuliani, Wei Xu, Peter Selby, Geoffrey Liu. Second-hand smoke (SHS) and smoking cessation in non-tobacco related cancers. [abstract]. In: Proceedings of the Thirteenth Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2014 Sep 27-Oct 1; New Orleans, LA. Philadelphia (PA): AACR; Can Prev Res 2015;8(10 Suppl): Abstract nr B15.