Juntendo Medical Journal

Objective: Gender differences in therapeutic and side effects of anticancer drugs have been reported. In our previous study with a small sample size, we reported that female patients are significantly more allergic than male allergic (Alg) patients to oxaliplatin (L-OHP), a platinum-based anticancer drug (platinum compound). On the other hand, there are no studies showing significant gender differences in drug allergy to non-anticancer drugs. And the presence of gender differences in drug allergy to anticancer drugs has not been established. In addition, there are studies showing an increase in peripheral white blood cell (WBC) count after Alg diseases and some drug allergy. However, there have been no studies on fluctuation of WBC count and blood cell fractionation in drug allergy to anticancer drugs. Therefore, in this study, with a larger sample size, we examined gender differences in drug allergy to anticancer drugs and fluctuation of WBC count and blood cell fractionation during Alg reactions. Materials: Between April 2016 and March 2019, 1,090 patients who were treated with four platinum compounds were retrospectively analyzed. Methods: Data obtained from the peripheral blood samples collected from each patient was used to determine WBC count. Results: A total of 35 patients were found to be allergic. The overall results for all platinum compounds showed a higher incidence of drug allergy in female patients than in male patients (p=0.049). The reactions were more pronounced in female patients receiving carboplatin (CBDCA)(p=0.034). In the Alg group, WBC count after Alg reactions was significantly higher (no statistically) and the percentage of neutrophils significantly increased (p=0.024), whereas the percentage of monocytes was significantly decreased (p=0.024). There were no gender differences in the incidence of leukocytosis before Alg reactions. However, the incidence of leukocytosis after Alg reactions was significantly higher in female patients than in male patients (p=0.031). Additionally, fluctuation in the percentage of blood cells, such as an increase in neutrophils (p=0.006) and a decrease in monocytes (p=0.023), were more prominent in female patients than in male patients. However, there was no statistically significant gender difference in the percentage of lymphocytes. Conclusions: This study revealed the possibility of gender differences in drug allergy to anticancer drugs including platinum compounds. Furthermore, this study showed new findings on fluctuation of WBC count and blood cell fractionation after Alg reactions.


Introduction
Gender differences in therapeutic and side effects of anticancer drugs have long been known 1) . A study showed that the efficacy of postoperative adjuvant chemotherapy with 5-fluorouracil, a cytotoxic anticancer drug, was higher in female colorectal cancer patients than in male colorectal cancer patients 2) . Another study showed that sensitivity to lenalidomide, an oral anticancer drug for relapsed or refractory mantle cell lymphoma, was higher in female patients than in male patients 3) . In the ECOG1594 study, in which patients with advanced non-small cell lung cancer were randomly assigned to four types of two-drug regimens including platinum-based anticancer drugs (platinum compounds), progression-free survival and median survival were significantly higher in female patients than in male patients 4) . Besides gender differences in the therapeutic effects of anticancer drugs, it is well known that the incidence of side effects of anticancer drugs, such as nausea and vomiting, is significantly higher in female patients than in male patients 1) . In addition, in the above-mentioned ECOG1594 study, not only nausea and vomiting but also alopecia and peripheral neuropathy were more frequently seen in female patients than in male patients 4) . There are other studies on the side effects of anticancer drugs. For example, a study showed a significantly higher incidence of decreased white blood cell (WBC) count and neutropenia after receiving the combination of a platinum compound (cisplatin [CDDP] or carboplatin [CBDCA]) and gemcitabine (GEM) in female non-small cell lung cancer patients than in male counterpart 5) . Another study reported a significantly higher incidence of neutropenia after receiving GEM in female pancreatic cancer patients than in male patients 6) . These studies suggest gender differences in the reactivity of blood cells, especially neutrophils (Neut), to drugs. However, the exact cause is unknown.
In a previous study with a small sample size (n = 81), we reported a significantly higher incidence of allergic (Alg) reactions after receiving oxaliplatin (L-OHP), a platinum compound, in female patients than in male patients 7) . On the other hand, in another study in 177 drug Alg patients, there were no statistically significant gender differences in Alg reactions to non-anticancer drugs, such as antibiotics, x-ray contrast medium, local anesthesia, and enzyme preparations 8) . Therefore, it is unknown whether there are gender differences in Alg reactions to drugs and whether these are limited to anticancer drugs. In addition, a higher incidence of basophilia in patients with bronchial asthma 9) and a higher incidence of eosinophilia in patients with Alg rhinitis 10) are widely known. Some studies showed a significant increase in peripheral WBC count after drug-induced Alg reactions 11)-13) . However, there are no studies of fluctuation of WBC count and blood cell fractionation after Alg reactions to anticancer drugs.
In this study with a larger sample size, we reexamined gender differences in Alg reactions to anticancer drugs and fluctuation of WBC count and blood cell fractionation during the reactions.

Patients
A total of 1,090 participants (5,746 cases mentioned) who received a regimen comprising four platinum compounds from April 2016 to March 2019 (3 years) were retrospectively analyzed. Participants were selected on the basis of electronic medical records for patients who discontinued treatment due to the development of Alg reactions (anaphylactic reaction, pruritus, rash/redness, dyspnea, etc.) after the start of anticancer drug administration. The non-Alg group had 35 patients (21 males and 14 females), with the highest number of treatment cycles (median, 15 cycles; range,  in this study, who were able to continue treatment with CBDCA and L-OHP for a longer period of time.

WBC count
Clinical laboratory data, obtained from peripheral blood samples collected from the patients, was used to determine the WBC count. Blood sample data of non-Alg patients was taken before the start of the first treatment (1st), at the 9 th cycle (9th)(when Alg occurrence was the most frequent), and before the final administration (Fin.) of the drug during this study period. On the other hand, for Alg patients, blood samples were also analyzed before Arii D, Nojima M: Gender difference in WBC in allergy the start of the first treatment (1st), before the onset (Bef.) of Alg, and after the onset of Alg (Aft.).

Methods
Statistical data analysis was performed with GraphPad Prism ® version 8.0 (GraphPad Software Inc., La Jolla, CA, USA) or JMP ® version 12.1.0 (SAS Institute Inc. Cary, NC, USA). Values were expressed as mean ± standard deviation (SD). The subject groups were compared using Mann-Whitney U test, and the chi-square test was used for frequency comparison. A probability of p < 0.05 was considered statistically significant.

Gender ratio of Alg patients treated with platinum compounds
The onset of Alg was examined in patients who received platinum compounds during the study period (Table-2). A total of 35 Alg patients (12 males and 23 females) were included in this study. There were significant gender differences in Alg reactions to platinum compounds (p = 0.049). No Alg reaction was found in patients who received CDDP or CDGP. Drug comparisons showed that the number of female patients treated with CBDCA was significantly higher (p = 0.034, Table-2).

Comparison of patient characteristics between
Alg and non-Alg patients Patient characteristics (i.e., gender, drugs used, age, the number of cycles, and cancer type) were compared between 35 Alg patients receiving platinum compounds (12 males and 23 females) and 35 non-Alg patients who were able to receive longterm administration of drugs (21 males and 14 females) (Table-3). The results showed a significant difference in the number of cycles between the two groups. In addition, there was a slight difference in the male to female ratio between the two groups. However, there were no statistically significant differences in drugs used and cancer type between the two groups.

Comparison of the fluctuation of blood cells between Alg and non-Alg patients
To investigate the relationship between the onset  of Alg and WBC, blood data from 35 non-Alg patients (14 males and 21 females) who were able to continue long-term treatment and receive platinum were first collected. As treatment progressed (from 1st to Fin), a decrease in WBC count was observed due to myelosuppression (p = 0.0001, Figure-1A; 9 th , and Fin). Similarly, the percentage of Neut also decreased significantly (p = 0.009, Figure-1B; 9 th ). In addition, the percentage of monocytes (Mono) showed an increasing trend but was not statistically significant in non-Alg patients ( Figure-1D; 9 th and Fin). On the other hand, as treatment progressed in Alg patients, a significant decrease in WBC was observed before the onset of allergies (p = 0.0063, Figure-1A; Bef.). Although not a statistically significant difference, the number of WBC in Alg patients showed an increasing trend after the onset of Alg ( Figure-1A; Aft.). The percentage of Neut in Alg patients did not show a significant decrease after the start of treatment but increased significantly after the onset of allergy (p = 0.024, Figure-1B; Aft.). In addition, the percentage of Mono at the Bef. stage in the Alg patients, similar to non-Alg patients, increased significantly compared to 1st, but the percentage of Mono at the Aft. stage decreased compared to Bef. (p = 0.024, Figure-1D; Bef. and Aft.). Overall, the percentage of lymphocytes (Ly) was not significantly different (Figure-1C).

Gender difference in the fluctuation of blood cells in Alg patients
It was compared the fluctuation of blood cells between male and female after Alg reactions to platinum compounds (CBDCA and L-OHP). The evaluation before and after Alg reactions showed no significant changes in male patients but an increase in WBC count in female patients was observed which was not statistically significant. Although there were no significant gender differences in WBC count before Alg reactions, WBC count in females increased more significantly after the onset of Alg compared to that in males (p = 0.031, Figure-

Discussion
We previously reported a gender difference in the incidence of Alg reactions to a platinum compound (L-OHP). This study with a larger sample size showed significant gender differences in the incidence of Alg reactions to a platinum compound (CDBCA)( Table-2), suggesting gender differences in the incidence of Alg reactions to anticancer drugs. Gender differences in drug metabolism may contribute to the results. There is a study showing a higher risk of severe drug eruption due to delayed drug metabolism after sensitization to unchanged drug or metabolites recognized as foreign bodies by immune cells 14) 15) . Generally, gender differences in drug metabolism involving anticancer drugs have also been reported 16) 17) . This suggests that differences in drug metabolism may cause gender differences in allergy expression. If gender differences in drug metabolism were the only cause of Alg reactions, anticancer drugs that have narrower therapeutic range and stricter dose constraints according to body weight and body surface area would lead to

Figure-1 Blood cells of allergic and non-allergic patients with platinum-based anticancer drugs
The number and ratio of WBC were calculated from the clinical laboratory data of peripheral blood samples collected from patients. The patients were divided into Alg (n = 35) and non-Alg (n = 35) groups. A represents WBC, B represents Neut, C represents Ly, and D represents Mono. Blood differential data immediately before the first anticancer drug treatment (1 st ), blood cells collected immediately before the 9 th when Alg occurrence is the most frequent (9 th ), immediately before each final administration in the study period (Fin.), before allergy (Bef.), After allergy (Aft.) is represented in the blood cell data collected. Mann-Whitney U test was used for significant test. Mean ± SD, significance level p < 0.05 ＊ , < 0.005 ＊＊ , < 0.0005 ＊＊＊ . less gender differences in Alg reactions than nonanticancer drugs that have large dose variations. However, there is no study showing gender differences in Alg reactions to non-anticancer drugs. In addition, this study demonstrated gender differences in Alg reactions to anticancer drugs. The results suggested that gender differences in Alg reactions to anticancer drugs involve differences in not only drug metabolism but also reactivity of immune cells. There is no study showing the association between immune cell reactivity and Alg reactions. However, our basic study in rats demonstrated gender differences in blood cell reactivity with antibodies (data not shown). In addition, some animal experiments showed gender differences in blood cells 18)-20) . Basic animal experiments only, it is unknown whether the findings can be applied to humans or not. Therefore, future studies should include further investigation of gender differences in immune cell reactivity and Alg reactions.
This study has some limitations, Firstly, this study failed to demonstrate significant gender differences in Alg reactions to L-OHP (unlike those to CBDCA), which we demonstrated in our previous study. This may be due to the lower incidence of Alg reactions to L-OHP in this study than that in our 2009 study 7) (6.3% vs. 18.5%). Although statistically not significant, the incidence of Alg reactions to L-OHP was 1.4 times higher in female patients than in male patients (7.7% vs. 5.6%). In addition, this study showed a significantly higher overall incidence of Alg reactions to Platinum compounds in female patients than in male patients ( This study examined fractionation of peripheral blood cells before and after Alg reactions to anticancer drugs in Alg patients, focusing on fluctuation of WBC count. Although not statistically significant, WBC count after Alg reactions was higher than that before Alg reactions (Figure-1A). There are studies showing a significant increase in WBC count in patients who had drug eruption or liver damage after receiving anticonvulsants such as phenytoin and valproic acid 12) 13) . On the other hand, this is the first study suggesting an increase in WBC count after Alg reactions to anticancer drugs. The study also showed a significant increase in Neut and a significant decrease in Mono after Alg reactions, but no significant changes in B cells that produce antibodies and are associated with Alg reactions (Figure-1B, C, and D). The results also showed significantly higher changes in WBC, Neut and Mono in female patients than in male patients ( Figure-2A, B, and D). This also showed gender differences in the above-mentioned immune cell reactivity, possibly leading to gender differences in Alg reactions. There is no study showing fluctuation in fractionation of blood cells after Alg drug reactions (e.g., anticancer drugs). Therefore, these fluctuations of blood cells are probably showing the new relationship between drug allergy and blood cells, though further investigations are needed.

Conclusions
This study showed gender differences in Alg reactions to anticancer drugs including platinum compounds and provided new findings of the fluctuation of WBC count and blood cell fractionation after Alg reactions. To maximize the effect of anticancer drugs in cancer patients, it would be helpful to provide long-term drug administration by reducing side effects of anticancer drugs (e.g., Alg reactions) 21) . However, in some cases, anticancer drugs induce severe Alg reactions and make it difficult to continue treatment. It is crucial to clarify the mechanism of Alg reactions, identify the predictors of Alg reactions, and establish prevention methods. We hope the findings of this study will help achieve these goals.