Purpose

Smoking is an established risk factor for colorectal cancer (CRC). The molecular profile of CRC in smokers may be different to non-smokers, which might contribute to the reported detrimental effects on disease free (DFS) and overall survival (OS). Not fully explored is differences in behaviour between smokers and non-smokers that might also affect outcomes.  

Patients and Methods

Using prospectively collected multidisciplinary data 2003-2014 from 3 Melbourne hospitals. Smoking history, demographics, diagnosis, treatment and outcomes were examined. Our focus was on patients ≤ 70 years old(yo) (due to the confounding of age) with early stage colon cancer; comparing current smokers with never-smokers.

Results

2521/ 4655 patients on the database had early stage colon cancer, 511 (20.3%) stage 1, 1120 (44.4%) stage 2 and 890 (35.3%) stage 3. 280 (11.1%) were current smokers, 769(30.5%) ex-smokers and 1472 (58.4%) never smokers.  Compared to never smokers, current smokers were younger (median age 62.73 vs 70.57, p=<.0001), predominately male (63.21% vs 42.32%, p=<0.001),with lower BMI (25.6% vs 26.7%, p=0.00014) and were more socially disadvantaged (IRSAD 997 vs 1022, p = <.0001).  For patients ≤ 70 yo the rate of screen detected cancers (14.6% vs 21.4%), stage at presentation (stage I, II, III 19.1,44.3,36.3% vs 19.5, 40.7,39.8%) and acceptance of adjuvant chemotherapy for stage III disease were 48.1 vs 50.8%. Adjuvant therapy completion rates were similar (34.4 vs 37.4). For patients ≤70 yo stages I-III combined, distant DFS was 83 vs 80% at 5 years, (HR 0.888, p = 0.5395) and OS 87 vs 86% at 5 years(HR 1.193, p = 0.0468 . Death without recurrence occurred in 22/42 (52%) vs 98/209 (47%). 

Conclusion

Smokers are less likely to have screen detected CRC, but accept and complete adjuvant therapy at similar rates to non-smokers. There is no impact of smoking on disease specific survival, with the excess of deaths in smokers due to non-CRC cancer deaths.