Can't lung cancer patients detoxify procarcinogens?

Background: Glutathione S-transferase mu (GST mu) enzyme detoxifies carcinogens in tobacco smoke. We assessed the clinical usefulness of serum assay of GSTm in determining the risk for lung cancer.
Materials and Methods: Fifty-nine patients with primary lung cancer and 32 control cases were enrolled. GSTm detection was performed by the method ELISA.
Results: GSTm enzyme positivity rate of the patient group (39%) was significantly lower than the control group (59.4%) (p < 0.05). The GSTm positivity rates were 28.6% for the non-smoker patients with a cancer history of relatives, 31.6% for the smoker patients with the cancer history of relatives, 14.6% for the non-smoker patients with the lung cancer history of relatives and 16.7% for the smoker patients with the lung cancer history of relatives.
Conclusions: We concluded that if the people lacking GSTm are smokers and have a cancer and/or lung cancer history among their relatives, they would challenge a greater risk of lung cancer than the individuals having GST mu isoenzyme.