The mean age of patients was 48 ± 11 years and 60% of them were premenopausal. The mean weight in Kgs was 81 ± 13 and the mean height in cm was 156 ± 5. Calculating BMI, the studied group of patients had mean of 33.8 ± 6.0. Mean BSA was calculated to be 1.84 ± 0.15. Comorbidities were present in 10.6% of patients. In the studied group of patients, tumors were more common of right side (55.7%), T2 tumor (40%), N1 (40.9%), and stage III in 57.4%. Regarding the hormonal receptor status, most of the patients were ER+ (76.5%), PR+ (66.1%) and Her2− (73.9%). The molecular subtypes were also estimated with HR+ subtype most common in (60%) and Her2+ subtype least common in (10.4%). Characteristics of the study population are shown in Table 1.

Mean BMI and BSA as defined per different variable were always of value more than 33 Kg/m² for BMI and 1.8 for BSA (Table 2).

Then BMI was set for a cut off value of 30 kg/m² and BSA was set at a cut off value of 1.85. Neither BMI nor BSA was different based on menopausal status. Tumor characteristics were compared in relation to BMI and BSA, and none of the studied parameters regarding menopausal status, T staging, N staging, TNM staging, ER, PR, Her2 and molecular subtype were significantly associated with BMI or BSA (Table 2 and Table 3).

Receiver operating characteristic (ROC) curve was done for the poor prognostic variables; namely: T3/4, N2/3, stage III, Her2+ subtype, and TN subtype. Analysis for predictive value of BMI or BSA Table 4, Figures 1-4 shows that both BMI

BMI: Body mass index, BSA: Body surface area, NA: not available, MRM: Modified radical mastectomy, BCS: breast conservative surgery, ER: Estrogen receptor, PR: progesterone receptor, Her2: Human epidermal growth factor receptor, HR+: hormonal receptor positive tumor, HR+/HER−: Hormonal receptor positive her-subtype, HER+: Her2 overexpressed subtype, TN: triple negative subtype.

^†One-way analysis of variance (ANOVA) SD = Standard deviation.

and BSA were poorly predictive for any of the prognostic tumor characteristics regarding T stage, N stage, Her2 overexpression and TN disease.

The mean BMI ± SD of patients in the current study was 33.8 ± 6.0. This means BMI is higher than the average recorded by the WHO for Egyptian female which is 30.7 kg/m² [21]. Hajian-Tilak et al. 2011 in a study on Iranian women reported a mean difference in BMI between breast cancer patients and normal controls of 4.6 kg/m² [22].

The figure of mean BMI recorded in the current study is higher than that recorded by Loi et al., 2005, [23] which was (24.5 kg/m²) in a study from Australia, and that reported by Ewertz et al. 2012, [24] in an analysis of the Breast International Group (BIG) 1 - 98 trial in which BMI had a mean of = 26.8 kg/m² ± 5.1 SD.

The mean age of patients was 48 years, and majority of them (73%) were obese (BMI ≥ 30 kg/m²) Shaaban et al. 2020 [25] in a multicenter trial from Egypt for a similar group of patients reported on mean age of 51.1 years and 60.5% with BMI ≥ 30 kg/m² [25]. Bouguerra et al. reported in a study on 262 Tunisian breast cancer patients that the mean age was 50.9 (±11.9) and 63.3% were with BMI ≥ 30 kg/m² [6]. Other studies reported a significantly less proportion of obese patients.

Kann et al., 2014 in a study from Switzerland reported a BMI of ≥ 30 kg/m² in 17% of patients [2]. Loi et al. 2005, reported on obese patients percentage of 12% [23], Lee et al. [26] in a study from Korea, reported on 4.3% obese patients and Ewertz et al. reported 23% obese patients (BMI ≥ 30 kg/m²).

Mean body surface area (BSA) also was high as the mean BSA was 1.85 m². This study to the best of our knowledge is the first to address BSA in Egyptian breast cancer patients. Sacco et al. 2010, in a study from England reported on BSA mean of 1.74 m² for breast cancer patients [16]. Dooley et al. in an Australian study, of 2838 chemotherapy scheduled patients reported mean surface area of 1.70 m² in female patients [27].

Sixty percent of the whole group were premenopausal. In the current study, 51/69 (74%) of premenopausal patients and 33/46 (72%) of postmenopausal patients were obese in terms of BMI ≥ 30 kg/m² representing around 3/4 of the whole group of patients to be obese regardless of menopausal status.

The mean BSA in premenopausal patients was 1.85 m² this could indicate the magnitude of the problem of obesity in younger age in Egyptian patients.

Unlike our results, Shabaan et al. [25] and Bouguerra et al. [6] reported on overweight and obesity to be more prevalent in postmenopausal patients. Still these figures coming from Egypt and Tunisia are higher than the reported from China where Wang et al. [7], reported on 23.8%, and 33.1% of premenopausal and postmenopausal respectively to be overweight and obese (BMI ≥ 25).

Rudat et al. 2013, in a multi-institutional study from Saudi Arabia reported on BMI to be lower in postmenopausal breast cancer patients compared to control individuals [28].

In the current study Tumor characteristics were compared in relation to BMI and BSA. There was a tendency of the poor pathologic features to be associated with high BMI and BSA, yet none of the correlations was of statistical significance. Patients with tumors 5 cm or larger (T3, 4), more than three involved LNs (N2, N3), and stage III disease were of high BMI (32/45) 71%, (32/49) 65% and (51/66) 77% respectively. The link between BMI and histopathological criteria was addressed in many African studies [6] [25] [29] [30]. Other studies [25] [31] [32] [33] [34] reported also on positive correlation between obesity and tumor size and high grade.

Wang et al. 2020, reported that obese patients were more likely to have lymph node metastases compared with non-obese patients in a retrospective review of 1352 breast cancer patients [7]. This point of view of association between obesity and increased number of involved axillary nodes was supported by others [35] [36]. On the other hand, nonstatistically significant association between BMI and number of involved axillary lymph node was also reported in many studies [6] [37] [38].

Association with larger tumor size and advancing grade of the tumor was also reported [2] [6] [38] [39] [40] [41].

In the current study no specific poor prognostic criterion was associated with menopausal status in obese patients. Wang et al. 2019 in a report from China reported that postmenopausal patients had less favorable tumor characteristics in form of more lymphovascular invasion and axillary lymph node metastasis [7].

Obesity was associated with less HR and HER2 positivity, so 8/27 were ER+, 10/30 PR+, and 7/30 were Her2+ but none reached statistical significance. Molecular subtypes of HR−/HER+ and TN were (9/12) and (11/16) respectively. similar to our results, Zhu et al. 2005, reported high BMI associated with ER− and TN disease [42]. Gierach et al., 2010, reported that high BMI was associated with less Her2 expression irrespective of ER status [43].

In the current study, molecular subtype was not affected by menopausal status in obese patients. Many studies reported that obese premenopausal tended to have hormonal receptor negative tumors and triple negative disease [7] [44] [45] [46] [47], and postmenopausal tended to have HR+ disease [2] [6] [47] [48] [49] [50].

The whole group of patients was obese. Trying to investigate the role of BMI and BSA as tools for predicting unfavorable characteristics of the tumor, ROC was done with AUC set to estimate whether obesity would predict the tumor being of poor prognostic feature or not. It was found that both BMI and BSA had poor predictive value in such matter. Bouguerra et al. reported on high sensitivity of BMI on the prediction of high grade tumors but not specific tumor subtype. Hajian-Tilak et al. 2011, in their study, ROC curves were able to predict cancer risk (AUC = 0.79) in both pre and postmenopausal females. But ROC was able to predict cancer risk in high BMI more than normal BMI patients. It was concluded that BMI had a predictive ability for breast cancer risk in both pre- and post-menopausal women [22].