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Chemotherapy Treatment Considerations in Special Patient Populations

TOP - August 2017, Vol 10, No 3

Anaheim, CA—The overtreatment or undertreatment of patients with cancer can have life-or-death implications. However, the risks are even higher in special patient populations, which may have worse outcomes without careful attention to their unique characteristics and needs, said Mary S. Mably, RPh, BCOP, Supervisor, Oncology Pharmacy Programs, UW Health, Madison, WI, at the 2017 Hematology/Oncology Pharmacy Association Annual Conference.

Dr Mably described strategies for improving chemotherapy management in rural populations, shared data regarding the safe use of chemotherapy during pregnancy, and summarized recommendations for the dosing of chemotherapy in obese patients. 

“Treatment of special populations with cancer remains challenging and ever-changing, but pharmacists can positively impact patient outcomes by familiarity with evidence and best-practice guidelines,” she said.

Access to Care in Rural Populations

Residing in rural counties has been associated with increased cancer mortality. In one study, patients with kidney cancer who lived in rural Illinois had higher rates of mortality, which the study researchers attributed to poorer access to care and later-stage diagnosis of disease in rural areas versus urban areas (Sadowski DJ, et al. Urology. 2016;94:90-95).

Difficulty in accessing cancer treatment can be caused by several factors, including increased travel time, limited availability of disease specialists or trained pharmacists and nurses, and the inconvenience in returning to an urban clinic for frequent treatment, said Dr Mably.

“Limited access to care can lead to delays in diagnosis and greater morbidity from disease,” she said. “Rural patients also have less access to investigational studies, specialty oral chemotherapies, and chemotherapies that require specialized administration techniques,” Dr Mably added.

Nevertheless, community pharmacists in rural areas that participate in oncology outpatient care have been shown to positively influence outcomes by providing access to medications, monitoring patients, and encouraging treatment adherence. In particular, oncology pharmacists may be able to provide long-distance counseling via telemedicine or telephone.

“Oncology pharmacists can educate rural patients on the importance of regular follow-up, help identify toxicities early to improve the effectiveness of care, and confirm access to oral anticancer agents,” said Dr Mably, who emphasized that the multidisciplinary participation in the care of this patient population is essential.

Pregnancy and Cancer Treatment

The diagnosis of cancer occurs in merely 0.02% to 0.1% of pregnancies, but this incidence is likely to increase in the future as a result of women becoming pregnant at a later age, said Dr Mably, who noted that cervical cancer is the most common type of cancer during pregnancy.

According to Canadian evidence-based clinical practice guidelines, chemotherapy agents have been shown to cross the placenta. Although exposure to these drugs after the first trimester is not associated with a greater risk for malformations, data show an increased risk for stillbirth, intrauterine growth restriction, and fetal toxicities.

However, despite these guidelines, evidence on the subject is limited. The National Comprehensive Cancer Network (NCCN) has included the treatment of cancer during pregnancy in some disease-specific guidelines as a special consideration, but these recommendations are incomplete, and pregnancy is still not included in most of the NCCN guidelines.

In addition, pregnant women face unique challenges in cancer diagnosis because of changes in physiology during pregnancy. For example, increased breast size during pregnancy make it difficult to detect lumps that may signify breast cancer. Furthermore, melanoma may be misdiagnosed as hyperpigmentation, which is often reported in pregnancies. There is also a reluctance to expose the fetus to unnecessary radiographic examinations that may help diagnose a woman’s cancer.

“Clinicians sometimes face disparate concerns regarding the safety of the fetus and adequate treatment of the mother,” said Dr Mably. “Rapidly dividing cells of the fetus, for example, are more susceptible to chemotherapy, and certain anticancer agents are proven to be human teratogens. Delays in treatment of cancer, on the other hand, may reduce survival of the mother,” she added.

Furthermore, even when treatment is initiated on time, it may not be sufficient. Using similar dosing in pregnant patients as in nonpregnant patients may lead to undertreatment as a result of increased volume of distribution, enhanced renal and hepatic elimination, and decreased albumin concentration, reported Dr Mably.

Dosing Chemotherapy in Obese Populations

As the number of patients with obesity and the degree of obesity continue to rise in the United States, calculating chemotherapy doses within this patient population has become increasingly problematic. The American Society of Clinical Oncology (ASCO) guidelines on chemotherapy dosing in obese patients with cancer recommend the use of full weight-based cytotoxic chemotherapy doses, especially for curative chemotherapy.

“In addition, ASCO states that myelosuppression appears to be the same in obese as in nonobese populations,” said Dr Mably. “The risk of undertreatment is very high [in obese patients with cancer], and there is no evidence for increased short- or long-term toxicity by using actual weight. Fixed dosing is appropriate for a few select agents, including bleomycin,” she added.

Doses of some agents for stem-cell transplantation have been increased beyond myelosuppression to the next dose-limiting toxicity. Furthermore, obese patients frequently have comorbidities that may affect drug toxicity or pharmacokinetics. However, supportive care and pharmacokinetic monitoring of some agents have helped to reduce the frequency of previously common adverse events, said Dr Mably.

“Future research on stem-cell transplant should include height, weight, BSA [body surface area], and BMI [body mass index] to allow assessments of clinical outcomes in this patient population,” she concluded.

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