Evaluation of the alkaline comet assay and urinary 3-methyladenine excretion for monitoring DNA damage in melanoma patients treated with dacarbazine and tamoxifen

Cancer Chemother Pharmacol. 2000;45(2):111-9. doi: 10.1007/s002800050018.


Purpose: To develop, using dacarbazine as a model, reliable techniques for measuring DNA damage and repair as pharmacodynamic endpoints for patients receiving chemotherapy.

Methods: A group of 39 patients with malignant melanoma were treated with dacarbazine 1 g/m(2) i.v. every 21 days. Tamoxifen 20 mg daily was commenced 24 h after the first infusion and continued until 3 weeks after the last cycle of chemotherapy. DNA strand breaks formed during dacarbazine-induced DNA damage and repair were measured in individual cells by the alkaline comet assay. DNA methyl adducts were quantified by measuring urinary 3-methyladenine (3-MeA) excretion using immunoaffinity ELISA. Venous blood was taken on cycles 1 and 2 for separation of peripheral blood lymphocytes (PBLs) for measurement of DNA strand breaks.

Results: Wide interpatient variation in PBL DNA strand breaks occurred following chemotherapy, with a peak at 4 h (median 26.6 h, interquartile range 14.75-40.5 h) and incomplete repair by 24 h. Similarly, there was a range of 3-MeA excretion with peak levels 4-10 h after chemotherapy (median 33 nmol/h, interquartile range 20.4-48.65 nmol/h). Peak 3-MeA excretion was positively correlated with DNA strand breaks at 4 h (Spearman's correlation coefficient, r=0.39, P=0.036) and 24 h (r=0.46, P=0.01). Drug-induced emesis correlated with PBL DNA strand breaks (Mann Whitney U-test, P=0.03) but not with peak 3-MeA excretion.

Conclusions: DNA damage and repair following cytotoxic chemotherapy can be measured in vivo by the alkaline comet assay and by urinary 3-MeA excretion in patients receiving chemotherapy.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenine / analogs & derivatives*
  • Adenine / urine
  • Adult
  • Aged
  • Antineoplastic Agents, Alkylating / adverse effects*
  • Antineoplastic Agents, Alkylating / therapeutic use
  • Comet Assay*
  • DNA Damage / drug effects*
  • Dacarbazine / adverse effects*
  • Dacarbazine / therapeutic use
  • Female
  • Humans
  • Lymphocytes
  • Male
  • Melanoma / drug therapy*
  • Melanoma / genetics
  • Middle Aged
  • Predictive Value of Tests
  • Sensitivity and Specificity
  • Skin Neoplasms / drug therapy*
  • Skin Neoplasms / genetics


  • Antineoplastic Agents, Alkylating
  • 3-methyladenine
  • Dacarbazine
  • Adenine