Smoking ups risk of death, metastasis, recurrence in prostate cancer
Prostate cancer patients who are current smokers at the time of primary curative treatment are at higher risk of cancer-specific mortality, metastasis and biochemical recurrence (BCR), according to a recent meta-analysis.
“These results should encourage radiation oncologists and urologists to counsel patients on smoking cessation, given the risk of poorer oncologic outcomes associated with smoking,” said researchers.
The meta-analysis included 22,549 prostate cancer patients, of whom 18.6 percent (n=4,202) were current smokers at the time of primary curative treatment and 81.4 percent (n=18,347) were nonsmokers. [JAMA Oncol 2018;doi:10.1001/jamaoncol.2018.1071]
A pooled analysis of 10 studies showed that current smokers had a significantly higher risk of BCR compared with nonsmokers (hazard ratio [HR], 1.40; 95 percent CI, 1.18–1.66; p<0.001). A similar detrimental effect of former smoking on BCR risk was also observed (seven studies; HR, 1.19; 1.09–1.30; p<0.001).
While a meta-analysis could not be performed due to heterogeneous data, researchers showed that smoking cessation for more than 10 years was a protective factor against BCR (HR vs current smokers, 0.6; 0.4–0.9; HR vs never smokers, 0.96; 0.68–1.37). Cessation for less than 10 years had no such effect.
Current smoking was likewise a significant risk factor for metastasis development, according to a pooled analysis of three studies (HR, 2.51; 1.80–3.51; p<0.001). In contrast, there was no association between former smoking and metastasis (HR, 1.61; 0.65–3.97; p=0.31).
The correlation between cancer-specific mortality and smoking was assessed in five studies. Pooled analysis showed that active smoking during primary therapy significantly increased the risk of cancer-specific mortality (HR, 1.89; 1.37–2.60; p<0.001), while former smoking did not (four studies; HR, 1.05; 0.81–1.37; p=0.70).
In addition, while smoking cessation for ≥10 years attenuated the negative effects of current smoking on cancer-specific mortality, patients who had a summarized dosage of ≥15 pack-years were at a higher risk of death (HR, 5.82; 1.96–17.30; p<0.001).
However, “[q]uantitative analyses on cumulative exposure and smoking cessation were not possible owing to the heterogeneity of data,” researchers pointed out.
Accessing the databases of PubMed, Medline, the Cochrane Library and Embase, researchers retrieved observational studies that investigated the effect of smoking on prostate cancer patients undergoing primary curative treatment. Only those that reported Cox proportional hazards regression or logistic regression analyses findings were eligible.
“Here, we identified a modifiable risk factor that may improve the outcome of patients with prostate cancer. In fact, smoking appears to affect all disease phases: recurrence, metastasis and [cancer-specific mortality],” said researchers, noting that physicians should counsel patients diagnosed with prostate cancer to stop smoking.
“Further studies with clear definitions of the study population and a precise assessment of the smoking exposure are needed to clarify the association of smoking cessation with long-term oncologic outcomes,” they added.