Radiation therapy and chemotherapy, separately or combined, are used worldwide to treat various types of cancer. Despite advances in medical technology, cancer patients experience various treatment-related ailments. For many years, it has been known that UV radiation from sun exposure is a major cause of skin cancer (Eide and Weinstock, 2005
). Radiation therapy, which uses ionising radiation, and chemotherapy use toxic agents that damage tissues and DNA (Eide and Weinstock, 2005
; Lopez et al, 2005
), often resulting in nausea, depression, fatigue, and impaired cognitive functioning (Hickok et al, 2005
; Knobf and Sun, 2005
). It was not surprising that cancer patients undergoing radiation therapy expect and experience skin reactions because treatment is administered through the skin. Skin problems are one of the most frequently reported side effects of cancer treatment. This comparative study provided insight into how skin pigmentation and pretreatment expectations influence post-treatment skin reactions reported by cancer patients.
Adverse skin reactions are commonly observed with various types of cancer treatment (Alley et al, 2002
). Common dermatologic manifestations from chemotherapy include alopecia, hyperpigmentation, hypopigmentation, erythema, and atrophy (Alley et al, 2002
). Radiation-induced skin reactions range from mild erythema to moist desquamation and necrosis. Additionally, some chemotherapeutic drugs sensitise the skin to radiation (Alley et al, 2002
). Our results showed no difference in the severity of skin reactions by treatment type (radiation therapy, chemotherapy, or both). However, black and white patients, regardless of the pretreatment expectations or diagnosis, differ in their perceptions of skin reactions and pain induced by cancer treatment. Although psychological factors are thought to play a role in disease burden and treatment response (Morse et al, 2003
; Olver et al, 2005
), our study did not demonstrate any relationship between pretreatment expectations and the report of post-treatment skin problems. Cancer patients receiving only radiation therapy expected more skin problems than cancer patients receiving chemotherapy or combination therapy.
Radiation-induced skin reactions are often unpredictable and vary by individual (Johansson et al, 2002
; Lopez et al, 2005
). Melanin, found in human skin, is considered to be protective against UV and ionising radiation (Nielsen et al, 2006
). Darkly pigmented skin contains more melanin than lightly pigmented skin. Melanin is an excellent absorber of UV radiation, and its concentration in the skin is strongly affected by UV radiation (Nielsen et al, 2006
). Untanned skin predominantly contains melanin in the basal layer of the epidermis, whereas tanned skin contains melanin throughout the epidermis. Melanin acts to remove free radicals and reactive oxygen species that are generated in skin by UV radiation (Hoogduijn et al, 2004
). Melanocytes, the cells that synthesise melanin, are more susceptible to the damaging effects of oxidative stress than other cell types in the skin, such as keratinocytes and fibroblasts (Hoogduijn et al, 2004
). Repeated exposure to UV or ionising radiation can disrupt melanin production and result in irreversible skin damage. Even though melanin can protect melanocytes and keratinocytes from oxidative DNA damage, in vitro
experiments have demonstrated that the presence of reactive oxygen species during melanin synthesis can increase DNA damage (Hoogduijn et al, 2004
). Therefore, darkly pigmented skin may be more susceptible to DNA damage from radiation due to the higher rate of melanin synthesis compared to lightly pigmented skin. Likewise, severe ionising radiation-induced skin reactions are often observed in sun-exposed regions of the skin (Harper et al, 2004
). Besides skin pigmentation, radiation-induced skin injury is also influenced by treatment area on the body (Stone et al, 2003
). The head and neck region, as well as the thorax region, are more prone to skin damage from radiation than the pelvic region of the body (Stone et al, 2003
). In this study, the black patients who reported post-treatment skin reactions were diagnosed with head and neck cancer (60%) and breast cancer (40%). Although diagnosis did not significantly correlate with the report of post-treatment skin reactions for white or black patients, the statistically significant difference in mean severity of skin reaction between the two racial backgrounds could be due to the dissimilar distribution of diagnoses. Future studies involving a larger population of black cancer patients would clarify these findings.
In this study, black patients reported more severe post-treatment skin reactions than white patients. Furthermore, the total radiation exposure directly correlated with the severity of skin reactions reported by black patients, but not by white patients. Therefore, the high melanin content of darkly pigmented skin did not appear protective. It is possible that skin reactions are not visualised in darkly pigmented skin until damage is more severe. For example, pinching of skin leaves a more easily visible red mark on fair-skinned individuals, because pigment interferes with the visualisation of redness in dark-skinned individuals. Additionally, radiation-induced disturbance of skin pigmentation would be more noticeable in more darkly pigmented skin.
Over the past few years, the influence of race (ancestry and physical characteristics) and ethnicity (behavioural and cultural distinctions) on the experience of pain has become a growing area of research (Edwards et al, 2001a
; Morse et al, 2003
). Many studies have demonstrated that black patients report higher levels of clinical pain and greater pain-related disability than white patients (Edwards et al, 2001a
; Campbell et al, 2005
). Additionally, racial differences in pain have been found to vary by anatomical site. For instance, black patients tend to report more pain associated with glaucoma, arthritis, orofacial injury, and migraine headaches (Riley et al, 2002
; Campbell et al, 2005
). Riley et al (2002
) and Sanders et al (1992)
showed that given the same pain stimulus, black patients had a stronger perception and response to the pain stimulus than white patients. Our study supported these previous findings by showing a direct correlation between the severity of self-reported pain and skin reaction at the treatment site in black patients, but not in white patients.
The therapeutic effects of ionising radiation are based on the greater capacity of normal tissues to repair DNA damage compared to rapidly proliferating tumour cells. Unfortunately, radiation treatment for cancer must be administered through the skin, (Harper et al, 2004
). Even though skin is not the target of treatment, it is damaged during the treatment process. Radiation-induced skin injury is influenced by treatment-related factors, such as volume of treatment area and fraction dose size, and by patient-related factors (Harper et al, 2004
). For instance, more severe radiation-induced skin problems occur in large-breasted women and obese individuals. Other patient-related risk factors for skin problems from cancer treatment include age, smoking status, infection of surgical wounds, and genetics (Harper et al, 2004
). Mutations in the ataxia-telangiectasia (ATM
) gene have been associated with increased radiosensitivity and radiation-induced morbidity (Iannuzzi et al, 2002
; Harper et al, 2004
heterozygosity occurs in approximately 1% of the general population and predicts subcutaneous late responses to radiation therapy, but not acute effects (Iannuzzi et al, 2002
). Therefore, patients containing a mutated ATM
gene might be predisposed to late radiation-induced skin injury. It is also known that point mutations and deletions in mitochondrial DNA (mtDNA) increase cellular radiosensitivity (Prithivirajsingh et al, 2004
). Unlike nuclear DNA, mtDNA lacks an efficient DNA repair mechanism and is more vulnerable to the accumulation of DNA damage (Prithivirajsingh et al, 2004
; Wilding et al, 2006
). High levels of mtDNA mutations in the skin could predispose cancer patients to radiation-induced skin problems. Unfortunately, we were unable to correlate the Symptom Inventory data with genetic alterations because the collection of blood and tissue samples from patients was not performed in this observational study based on clinical data. Next steps in understanding the differences observed in this study would include assessing the relationship of our findings to these known contributors to radiation sensitivity. These explanations for the difference in the severity of post-treatment skin reactions reported by black and white patients should be explored in a future clinical study.
Although this comparative study was able to demonstrate statistically significant racial differences in the severity of post-treatment skin reactions and pain reported by cancer patients, black subjects were underrepresented in both surveys in comparison to white subjects. The small sample size of black patients could have biased the statistical results, especially if these individuals represent extremes of the general population. Further clinical studies should include a larger sample population of black patients to determine more precisely the distribution of reported post-treatment skin reactions and pain in black and white patients. Additionally, a larger sample size would increase the statistical power and validity of the results, as well as the ability to understand specific consequences of treatments such as anti-epidermal growth factor receptor therapy, which commonly cause an acne-like rash (Sipples, 2006
). Additionally, future studies would benefit from extensive clinical data, such as disease stage, area of treatment, documentation of skin problems, and blood samples to examine predisposing genetic factors. Our study did show similar trends in two separate surveys (national and local); both suggesting that black and white patients differ in their perception of skin reactions and pain induced by cancer treatment. Further elucidation of the role of skin pigmentation and the influence of race and ethnicity on skin reactions and pain experienced by cancer patients could improve cancer treatment symptom management for future patients.