Q&A: Cytotoxic Medications and Cancer

Cytogenetics is the study of the structure and function of chromosomes in relation to phenotypic expression. Chromosomal abnormalities underlie the development of a wide variety of diseases and disorders ranging from Down syndrome to cancer, and are of widespread interest in both basic and clinical research.

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This is a Question & Answer revision article designed for medical students and professionals preparing for the PLAB, MRCP or USMLE examinations. They are based on actual questions from these examinations. You may find the Cancer article more useful, or one of our many articles on Diseases & Conditions, Medical Syndromes, Health & Wellness or Home Remedies.

In this article:
Role of cytotoxics in causing cancer
MCQ exam: clinical scenario
MCQ exam: answer
MCQ exam: explanation

Role of cytotoxics in causing cancer

The chemotherapy of cancer is complex and should be confined to specialists in oncology. Cytotoxic drugs have both anti-cancer activity and the potential to damage normal tissue; most cytotoxic drugs are teratogenic.

Many people who have had cancer treatment have a risk of developing long-term side effects. These side effects can happen months or years after treatment. Evaluating and treating late effects is an important part of cancer survivorship care.

Secondary cancers may develop as late side effects of earlier cancer treatments. This may be a new primary cancer. It may develop as a late effect of previous cancer treatments, such as chemotherapy and radiation therapy. Or it may be the original cancer that has spread to other parts of the body from where it started.

Chemotherapy and radiation therapy can also damage bone marrow stem cells. This increases the risk of either acute leukemia or myelodysplasia. Myelodysplasia is a blood cancer where the normal parts of the blood are either not made or are abnormal. Talk with your doctor about any new symptoms or side effects that you experience.

MCQ exam: clinical scenario

Cytogenetic abnormalities are a known side effect of several cytotoxic drugs.

Which of the following cytotoxic drugs is most likely to lead to endometrial cancer ?

a) tamoxifen
b) 5-fluorouracil
c) taxoids
d) cyclopentenyl cytosine
e) trastuzumab

MCQ exam: answer

The correct answer is A.
Of the given options, Tamoxifen is the most strongly associated with endometrial cancer.

MCQ exam: explanation

Long term use of tamoxifen has been associated with an increase in endometrial cancer. Other unintended effects of Tamoxifen include:

• Endometrial changes. Increased endometrial changes, including hyperplasia, polyps, cancer, and uterine sarcoma reported; prompt investigation required if abnormal vaginal bleeding including menstrual irregularities, vaginal discharge, and pelvic pain or pressure in those receiving (or who have received) tamoxifen.
• Risk of thromboembolism. Tamoxifen can increase the risk of thromboembolism particularly during and immediately after major surgery or periods of immobility (consider interrupting treatment and initiating anticoagulant measures).
• Conception and contraception. Unless being used in the treatment of female infertility, effective contraception must be used during treatment with Tamoxifen and for 2 months after stopping. Patients being treated for infertility should be warned that there is a risk of multiple pregnancy (rarely more than twins).

Reference(s)
1). British National Formulary (BNF): Tamoxifen. Available online: https://bnf.nice.org.uk/drug/tamoxifen.html#sideEffects
2). British National Formulary (BNF): Cytotoxic drugs. Available online: https://bnf.nice.org.uk/treatment-summary/cytotoxic-drugs.html
3). American Society of Clinical Oncology (ASCO): Long-Term Side Effects of Cancer Treatment. Available online: https://www.cancer.net/survivorship/long-term-side-effects-cancer-treatment