Prevalence of iron and Vitamin B12 deficiencies and inflammatory anemia in treatment-naive patients with cancer: A cross-sectional study

Avinash Pandey; Raj Aryan; Murari Krishna; Shivkant Singh; Piyush Pankaj

doi:10.4103/CRST.CRST_248_20

ORIGINAL ARTICLE

Year : 2020 | Volume : 3 | Issue : 4 | Page : 708-715

Prevalence of iron and Vitamin B₁₂ deficiencies and inflammatory anemia in treatment-naive patients with cancer: A cross-sectional study

Avinash Pandey¹, Raj Aryan², Murari Krishna², Shivkant Singh², Piyush Pankaj²
¹ Department of Medical Oncology, All India Institute of Medical Sciences, Patna, Bihar, India
² Department of Medical Oncology, State Cancer Institute, Indira Gandhi Institute of Medical Sciences, Patna, Bihar, India

Date of Submission	19-Jul-2020
Date of Decision	29-Jul-2020
Date of Acceptance	21-Sep-2020
Date of Web Publication	25-Dec-2020

Correspondence Address:
Avinash Pandey
Department of Medical Oncology, All India Institute of Medical Sciences, Patna, Bihar
India

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/CRST.CRST_248_20

Abstract

Background: Anemia in patients with cancer has been associated with poor outcomes. There are scarce data on the prevalence of iron and Vitamin B₁₂ deficiencies and inflammatory anemia among treatment-naive patients in the Indian setting.
Objectives: In this study, we aimed to evaluate the prevalence of anemia and iron and Vitamin B₁₂ deficiencies along with inflammation in treatment-naive patients.
Materials and Methods: This single-center cross-sectional study was conducted at the Indira Gandhi Institute of Medical Sciences (Patna, India) from July 2019 to December 2019. All patients registered in the Medical Oncology Department were offered testing for iron profile and serum Vitamin B₁₂ and serum ferritin levels. Anemia was defined as hemoglobin level<11 g/dL. Transferrin saturation<20%, serum ferritin >300 mg/L, and Vitamin B₁₂ level<200 pg/ml were the “cutoffs” used to define iron deficiency, inflammation, and Vitamin B₁₂ deficiency, respectively. Data were analyzed using descriptive statistics in the SPSS version 17.0. Pearson's Chi-squared test and odds ratio were used to measure the strength of association of anemia with the variables.
Results: We included 311 patients in the study, of which 167 (54%) were men. The median age of the cohort was 52 ± 15.9 years (range, 18–84). The prevalence of anemia was found to be 61% ± 2.7 (95% confidence interval, 55–66%). The mean hemoglobin level of the cohort was 9.86 ± 2.08 g/dl (range, 3–16). Of 311 patients, 21 (7%) had severe anemia (hemoglobin<6.9 g/dl). Iron deficiency, inflammation, and Vitamin B₁₂ deficiency were noted in 135/189 (71%), 61/189 (32%), and 89/189 (47%) anemic patients, respectively. Over 70% of the patients with gastrointestinal, gynecological, and lung cancers had an underlying iron deficiency.
Conclusions: Two-thirds of our Indian patients with cancer are iron deficient, whereas half and one-third of them have Vitamin B₁₂ deficiency and inflammation, respectively.

Keywords: B12 deficiency, cancer anemia, inflammatory anemia, iron deficiency, nutritional anemia

How to cite this article:
Pandey A, Aryan R, Krishna M, Singh S, Pankaj P. Prevalence of iron and Vitamin B₁₂ deficiencies and inflammatory anemia in treatment-naive patients with cancer: A cross-sectional study. Cancer Res Stat Treat 2020;3:708-15

How to cite this URL:
Pandey A, Aryan R, Krishna M, Singh S, Pankaj P. Prevalence of iron and Vitamin B₁₂ deficiencies and inflammatory anemia in treatment-naive patients with cancer: A cross-sectional study. Cancer Res Stat Treat [serial online] 2020 [cited 2021 May 8];3:708-15. Available from: https://www.crstonline.com/text.asp?2020/3/4/708/304953

Introduction

Anemia in patients with cancer is associated with inferior outcomes, including poor survival and diminished quality of life.^[1],[2],[3] Blood loss, malnutrition, hemolysis, chronic inflammation, bone marrow suppression, and decreased erythropoiesis can independently or in unison cause a drop in the hemoglobin levels among patients with cancer.^[3],[4] Treatment with chemotherapy or radiotherapy can further compromise red blood cell mass, and patients with advanced-stage tumors often have a higher prevalence of anemia.^[4],[5] Further, the prevalence of anemia among patients with cancer may vary considerably across different countries and hence needs to be studied in a population-specific manner.^[6],[7],[8]

Most of the published studies have primarily focused on the iron-deficiency aspect of cancer-related anemia and its subsequent remedial therapeutic options, including iron supplementation and blood transfusions.^{[2],[6],[7],[8]} A more comprehensive effort with other possible co-variables, such as vitamin deficiencies and chronic inflammation, is merited to discover other salient but inconspicuous causes of pretreatment cancer anemia. In this Indian cross-sectional study, we aimed to evaluate the prevalence of the underlying iron and Vitamin B₁₂ deficiencies and chronic inflammation, in newly diagnosed, treatment-naive adult patients across several cancer types, irrespective of their hemoglobin status.

Materials and Methods

General study details

This was a single-center, cross-sectional study on treatment-naive adult patients with cancer registered in the Department of Medical Oncology at the Indira Gandhi Institute of Medical Sciences, a regional cancer center in Patna, India, from July 1, 2019, to December 31, 2019. Written informed consent was obtained from each participant before enrollment in the study. The study was conducted in accordance with the Declaration of Helsinki and the Indian Council of Medical Research (ICMR) guidelines for ethical conduct. As per our institutional policy, observational and cross-sectional studies do not require an approval from the Institutional Ethics Committee. No funding was received for conducting this study.

Participants

All consecutive adult patients aged more than 18 years, irrespective of their type of malignancy were enrolled in this study. We included patients who had a diagnosis of malignancy and its type confirmed by cytology, biopsy, serological tumor markers, or flow cytometry either at the time of enrollment or within 2 weeks of enrollment. Patients who had received prior anticancer therapy including chemotherapy, hormonal therapy, radiotherapy, or any major surgery, except diagnostic biopsy/cytology, were excluded from the study. In addition, pregnant women and those with chronic renal failure; decompensated liver cirrhosis; inflammatory bowel diseases; history of major gastric or bowel resection; active life-threatening infection; chronic active infections such as tuberculosis and leishmaniasis; and active rheumatological or flared up connective tissue disorders such as rheumatoid arthritis, spondyloarthropathies, systemic lupus erythematosus, scleroderma, and sarcoidosis were excluded.

Patients with documented psychiatric conditions interfering with diet such as anorexia nervosa or bulimia were also excluded. Patients with a history of prior prescription of oral/parenteral iron or B₁₂ supplementation in the preceding 3 months were excluded. Similarly, patients with a history of blood transfusion in the past 1 month were excluded. Patients with a history of chronic gastrointestinal bleeding, including any tumor-related events such as bleeding per vaginum or hemoptysis, hematemesis, or hematuria, however, were eligible to participate in the study.

Variables

Our primary aim was to determine the prevalence of anemia, iron and Vitamin B₁₂ deficiencies, and chronic inflammation in patients with cancer before receiving any cancer-directed therapy.

Study methodology

Sample collection and processing

Apart from the routine pretreatment investigations such as complete hemogram, serology, coagulation profile, and renal and hepatic function tests, we also obtained peripheral venous blood samples to assess the serum iron, serum ferritin, total iron-binding capacity, transferrin saturation (TSAT), and serum B₁₂ levels. A total of 3 ml blood was drawn from an accessible peripheral vein in an aplastic tube with or without a gel barrier (red or yellow top serum separator vacutainer), irrespective of fasting or special dietary requirements. Serum was separated from the red blood cell clot and stored at 2–8°C if the sample was to be processed on the same day or at –20°C if it was to be processed on a later date. Samples with gross hemolysis, fibrin, or particulate matter were excluded from the analysis. Samples once thawed were mixed thoroughly by low-speed vortexing or by inverting the tube ten times. Specimens were centrifuged at 3000 rpm for 10 min in centrifugation tubes to maintain consistency in results. The clear supernatant without bubbles was collected after centrifugation for further processing. For sample processing, glass tubes were not tested. The average turnaround time for the reports was 24–48 h.

For serum iron estimation: The MULTIGENT iron assay intended for the direct colorimetric determination of iron without deproteinization from human serum using the ARCHITECT cSystems was used. The iron assay is standardized against the National Institute of Standards and Technology Standard Reference Material 3126
For serum ferritin levels: The ARCHITECT Ferritin assay, a chemiluminescent microparticle immunoassay, was used for the quantitative determination of ferritin in human serum using the ARCHITECT iSystems. The Ferritin assay is standardized against the World Health Organization (WHO) Ferritin First International Standard 80/602
For transferrin: The transferrin assay which is an immunoturbidimetric procedure for the determination of transferrin in human serum using the ARCHITECT cSystems was used. The transferrin assay is standardized against the reference method calibrated against ERM-DA470.80/602
For serum B₁₂ levels: The ARCHITECT B₁₂ assay was used which is a chemiluminescent microparticle intrinsic factor assay for the quantitative determination of Vitamin B₁₂ in human serum using the ARCHITECT iSystem. Abbott manufactures B₁₂ internal standards gravimetrically using cyanocobalamin (USP Reference Standard). The B₁₂ calibrators are manufactured and tested against these internal standards.

Data collection

Demographic data including age, sex, type of malignancy, and disease stage were recorded. Anemia was classified as per the ICMR definition as mild (hemoglobin: 10.9–10 g/dl), moderate (hemoglobin: 9.9–7 g/dl), severe (hemoglobin: 6.9–4 g/dl), and very severe (hemoglobin:<4 g/dl) anemia.^[9] Anemia was also classified based on the mean corpuscular volume as microcytic (<79.9 fL), normocytic (80–100 fL), and macrocytic (>100.1 fL) anemia.

Definitions

To maintain uniformity in the methods of assessment, we defined iron deficiency as TSAT<20%.^[10] Patients were considered to have inflammatory anemia if their serum ferritin levels were > 300 mg/L with TSAT > 20%.^[11] Vitamin B₁₂ deficiency was defined as serum B₁₂ levels<200 pg/ml.^[12] All patients were categorized as iron deficient, B₁₂ deficient, or as having an inflammatory state, regardless of whether they had anemia, using the above definitions. Of note, there is no single, uniform, and universally accepted definition of anemia of chronic disease, and it is essentially a diagnosis of exclusion, after ruling out nutritional, hemolytic, and other standard causes of anemia. It is useful to consider TSAT for patients in whom the serum ferritin level is 100–300 ng/mL, and an iron deficiency has to be ruled out; in such cases, TSAT < 20% points toward an iron deficiency. Our definition/cutoff of serum ferritin > 300 ng/mL as the inflammatory state precluded the requirement of TSAT to define iron deficiency.

Patient management protocol

Our threshold for packed cell transfusion was a hemoglobin level of<7.0 g/dl, unless impending cardiac or renal morbidity, major active bleeding, clinical decision, or sepsis merited a reduction in the transfusion threshold. At the time of recording the hematological reports (within 2 weeks of registration), including the complete hemogram, iron profile, and serum B₁₂ levels, patients who were found to be anemic and had iron or Vitamin B₁₂ deficiencies were given the option to receive supplementation. Patients were prescribed either intravenous injectable ferric carboxymaltose (1000 mg flat dose) or ferrous sulfate capsules (100 mg) 3 times a day for 6 months. None of the patients were prescribed erythropoietin-stimulating agents (ESAs). Similarly, patients with Vitamin B₁₂-deficient anemia were prescribed 1000 mg intramuscular injection of cyanocobalamin once daily for 7 days, followed by once a week for 1 month and once a month for 6 months. However, patients were not followed up to check the compliance or to assess the change in the hemoglobin level, as this was beyond the purview of our study. We did not define or measure any clinical, hematological, or serological endpoint for later follow-up, irrespective of the deficient store replenishment status, as this was a single-point cross-sectional study to determine only the prevalence.

Statistics

A formal sample size calculation was not done, and all the registered patients from July 1, 2019, to December 31, 2019, were assessed for eligibility for this study. Patients for whom the iron profile and Vitamin B₁₂ level were ordered but the reports were not traceable due to technical failure or not reported (n = 18) were classified as those with missing data. The missing data were spread randomly [Flowchart 1]. The probability of data being missing was considered to be the same for all the cases, and hence, the pattern of missing data was classified as missing completely at random. The cases with missing data were subject to list-wise deletion for the final analysis bringing down the sample size to 311. As a result, the estimated parameters including the prevalence of anemia were not subject to a bias due to the absence of the missing data.

All the data were recorded in real time in the Outpatient Department of Medical Oncology by a trained data entry operator under the supervision of the physician. Descriptive statistics, including tables, Venn diagram, charts, and frequency distribution, were derived from SPSS software version 17.0 (IBM Corp. Released 2017. IBM SPSS Statistics for Windows, version 17.0. Armonk, NY, USA). Pearson's Chi-squared test was used to analyze the association of anemia with several relevant categorical variables. Odds ratio was calculated to measure the strength of association, if any.

Results

Patient characteristics

Out of 441 patients screened and offered baseline iron profiling and serum Vitamin B₁₂ estimation, only 311 were finally enrolled in the study [Figure 1]. The median age at diagnosis was 52 ± 15.9 (range, 18–84). About 79% of the patients had advanced stage (III/IV) cancers [Table 1].

Figure 1: Flowchart for participant accrual and eligibility for the study

Click here to view

Table 1: Demographic variables of patients enrolled in the study

Click here to view

Anemia profile

The prevalence of anemia in treatment-naive patients with cancer was 61% ± 2.7 (95% CI, 55%–66%) [Table 2]. Iron deficiency, inflammation, and Vitamin B₁₂ deficiency were observed in 135/189 (71%), 61/189 (32%), and 89/189 (47%) anemic patients, respectively [Table 3]. Across several major cancer sites/types, anemia was observed in 42/59 (71%) patients with hematolymphoid malignancies, 40/69 (58%) with gastrointestinal malignancies, 35/59 (59%) with breast cancer, 24/35 (68%) with gallbladder cancer, 16/24 (66%) with gynecological cancers, and 11/22 (50%) with lung cancer. More than 70% of the patients with gastrointestinal (50/69), gynecological (17/24), and lung cancers (18/22) had an underlying iron deficiency [Figure 2]. A considerable number of patients (5%) had concurrent iron deficiency, B₁₂ insufficiency, and chronic inflammation [Figure 3].

Table 2: Anemia and the corresponding laboratory variables including the iron profile and Vitamin B₁₂ values

Click here to view

Table 3: Anemia status with respect to iron deficiency, chronic inflammation, and Vitamin B₁₂ serum levels

Click here to view

Figure 2: Proportion of patients with iron deficiency, inflammation, and Vitamin B12 deficiency across different cancer types/sites

Click here to view

Figure 3: Venn diagram for serum iron, Vitamin B12 deficiency, and inflammation showing overlap among the three entities

Click here to view

Association of variables with anemia

Iron deficiency was found to be strongly associated with anemia with a Pearson's Chi-square value of 8.05 (P = 0.005) and odds ratio of 1.98 (95% CI, 1.23–3.195). Similarly, chronic inflammation was found to be significantly associated with anemia with a Pearson's Chi-square value of 4.13 (P = 0.042) and odds ratio of 1.72 (95% CI, 1.02–2.90). Women were found to have a higher predilection for anemia with a Pearson's Chi-square value of 4.90 (P= 0.027) and odds ratio of 1.67 (95% CI, 1.06–2.65) compared to men. There was no statistically significant association between underlying Vitamin B₁₂-deficiency anemia (Pearson's Chi-square value of 2.48 [P = 0.115] and odds ratio of 1.45 [95% CI, 0.91– 2.30]). Similarly, neither older age (more than 60 years or less) nor the type of malignancy (hematological or solid cancers) had a significant association with anemia.

Supplementation for anemia

Out of 21 patients with hemoglobin<7 g/dl, blood transfusions were given to 19 (90%) patients within 2 weeks of getting registered, while one patient declined and another defaulted. Of 135 patients, 122 (90%) were prescribed iron supplementation, whereas 9 declined, 3 defaulted, and 1 died by the 2^nd week of registration. Of the 122 patients who received iron supplementation, 84 (69%) received intravenous iron along with intravenous chemotherapy, while 38 (31%) preferred oral iron capsules. Of 89 patients with Vitamin B₁₂-deficient anemia, 58 (65%) received intramuscular cyanocobalamin for at least 7 days, 19 (21%) received it for<7 days, while the remaining 12 (14%) declined supplementation.

Discussion

In this cross-sectional study, we found that the prevalence of anemia in adult, treatment-naive Indian patients with cancer was 61% ± 2.7 (95% CI, 55–66%) with the mean hemoglobin level for the entire population of 9.86 ± 2.08 (range, 3–16). Among patients with anemia, 71% had an underlying iron deficiency, 32% had inflammation, and 47% had a Vitamin B₁₂ deficiency. A vast majority of the patients (70%) with gastrointestinal, gynecological, and lung cancers had an underlying iron deficiency. To the best of our knowledge, this is the first cross-sectional study across different cancer types in adult patients from India to report the prevalence of underlying pretreatment anemia.

In one of the largest prospective observational studies conducted in 24 European countries in 15367 patients with cancer spread across 248 centers, the prevalence of anemia at enrollment before cancer-directed therapy was 31.7%.^[13] In this study, anemia was defined as hemoglobin<12.0 g/dl as per the American Society of Clinical Oncology and Common Toxicity Criteria, National Cancer Institute.^[14],[15] Anemia was observed in more than 70% of the patients with lung cancer or gynecological malignancies either at baseline or at some time point within 6 months from enrollment, including the treatment period.^[13] In another observational study reported from Italy and Austria, the prevalence of anemia was found to be 32% with a hemoglobin cutoff of 10.0 g/dl.^[7] In this study, majority of the patients (80%) had solid malignancies and 13% had use derthropoeisis-stimulating agents (ESA) for resolution of symptoms. Both the studies also reported the use of iron (oral or intravenous) supplementation apart from blood transfusion and ESA for patients with anemia. However, these studies did not report the baseline iron stores, serum ferritin levels as marker of inflammation, or serum Vitamin B₁₂ levels to establish the exact cause and contribution of the above three etiologies to the pathophysiology of anemia in treatment-naive patients with cancer. There is a paucity of similar comprehensive observational studies evaluating the prevalence of anemia in treatment-naive patients from the Indian subcontinent.

The prevalence of anemia varies widely across different continents and countries. The WHO estimates the prevalence of anemia in the general healthy population to be 23% in Europeans and 45%–47% in Africans and South-East Asians.^[16] In India, the prevalence of anemia also differs among the various high-risk groups such as preschool children (74%), school girls (50%), and pregnant women (52%).^[16],[17] Hence, it is pertinent to have country- or state-specific studies to elicit the prevalence of anemia, especially among the high-risk group such as newly diagnosed patients with cancer. Few attempts have been made across various cancers in India and reported prospectively. In a study conducted in 96 newly diagnosed and treatment-naive patients with lung cancer in a single center in South India, the prevalence of anemia was observed to be 61.4%.^[18] In another large prospective study done exclusively in 316 newly diagnosed patients with lymphoid malignancies recruited over 18 months, the prevalence of anemia was 42.4%.^[19] Nutritional deficiency was reported to be the cause of anemia in less than half of the anemic patients with cancer.

In the Regional Cancer Centre of our institute, the Medical Oncology Department comprises a single faculty and single point of contact for all solid and hematological malignancies registered for receiving chemotherapy.^[20] This provides a unique vantage point offering a “bird's eye view” of several cancer subtypes being treated under one roof, unlike many apex cancer centers where site and subsite super-specializations lead to restricted disease management patient pool. Our observational cross-sectional study included 311 consecutive adult patients with cancers of all major sites/types. The observed prevalence of anemia in our study was 61%. This is in accordance with our previous published study on treatment-naive patients with cancer, where the prevalence of Vitamin D deficiency was 67%.^[21],[22] This highlights the fact that poor nutrition is the major factor leading to cancer anemia and Vitamin D deficiency.

In our study, a higher number of patients (71%) with hematolymphoid malignancies had underlying anemia at presentation. In the absence of a hematology department, majority of the patients with hematolymphoid malignancies are seen by the medical oncology unit. In the current study, patients with hematolymphoid malignancies comprised 19% (59/311) of the cohort.^[23],[24] Gallbladder cancer is the most common cancer type in this part of India.^[25] The prevalence of anemia in patients with gallbladder and gastrointestinal malignancies in our study was 68% and 58%, respectively, at presentation. Compared to the European studies, one of the reasons for a higher prevalence of anemia in our study was presentation of a considerable proportion of patients (245/311, 79%) at a more advanced disease stage (III and IV), which reflects late presentation and aggressive biology.^{[7],[13],[26]}

Our study has several limitations. We only measured the laboratory values of hemoglobin, iron profile, and serum B₁₂ levels but did not elicit the nature, type, or severity of the symptoms related to cancer anemia such as fatigue, anorexia, breathlessness, palpitation, or bleeding. As ours was a noninterventional study, the decision to take iron or B₁₂ supplementation was based on the patients' discretion and was not controlled, directed, or followed by our team. Being a single-time point cross-sectional study, we did not follow up the patients longitudinally to study further drop in their hemoglobin levels due to cancer-directed therapies or the extent of rise in the hemoglobin level and time taken to improve the anemic status after any supplementation. This is also the reason that we could not analyze the treatment response, toxicities, outcomes, or survival across different cancer types with respect to the anemia status at baseline.

Our study is the single largest institutional analysis reporting the prevalence of anemia in Eastern India. However, our reported prevalence may not be representative of the prevalence of anemia in the metropolitan cities and western and southern regions of India. In our study, the target population was strictly defined as per the eligibility criteria, and hence, generalizability and external validity of our results beyond the defined population cannot be guaranteed, especially with respect to diverse geographical, temporal, and ethical conditions. In a retrospective clinical audit done before finalizing the protocol for the current study, it came to our notice that serum folate levels were not reported consistently by our institutional laboratory. On further exploration, we discovered that procurement and supply chain of folate assays were inconsistent due to several logistic issues leading to inadequate reporting. Hence, we did not include the serum folate measurements in our study. Moreover, exclusive folate deficiency with normal B₁₂ levels alone as the cause of anemia is seen in<2% of the patients with cancer.^[19] However, a separate comprehensive study is merited to evaluate its independent significance in treatment-naive patients with cancer with underlying anemia.

The definition of inflammatory anemia mandates the exclusion of iron and Vitamin B₁₂ deficiency and the presence of inflammatory state in anemic patients.^[27],[28] We used serum ferritin above 300 ng/mL as a uniform cutoff to measure inflammatory anemia, after excluding iron and Vitamin B₁₂ deficiency, as this value is beyond the upper limit of the normal range. Measurement of soluble transferrin receptor (sTfR) and/or sTfR-ferritin index is the most effective way to define anemia of inflammation and distinguish between anemia of inflammation and existing iron deficiency.^[29] However, the measurement of sTfR was beyond the scope of our laboratory and the context of the current study.

Conclusion

Anemia is prevalent in 60% of the treatment-naive adult patients with cancer. Iron deficiency, Vitamin B₁₂ deficiency, and chronic inflammatory state are seen in two-thirds, half, and one-third of the patients, respectively. Identifying the cause of anemia at presentation, including nutritional deficiencies, may improve the hemoglobin after supplementation. Whether such pretreatment detection of deficiencies and their subsequent correction impacts cancer outcomes and treatment toxicities favorably needs to be explored prospectively in future studies.

Acknowledgements

We would like to thank Dr. Ruchi Kapoor, Oncquest Laboratories, New Delhi, India.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

References

1.	Caro JJ, Salas M, Ward A, Goss G. Anemia as an independent prognostic factor for survival in patients with cancer: A systematic, quantitative review. Cancer 2001;91:2214-21.
2.	Kanuri G, Sawhney R, Varghese J, Britto M, Shet A. Iron deficiency anemia coexists with cancer related anemia and adversely impacts quality of life. PLoS One 2016;11:e0163817.
3.	Lind M, Vernon C, Cruickshank D, Wilkinson P, Littlewood T, Stuart N, et al. The level of haemoglobin in anaemic cancer patients correlates positively with quality of life. Br J Cancer 2002;86:1243-9.
4.	Harrison LB, Shasha D, White C, Ramdeen B. Radiotherapy-associated anemia: The scope of the problem. Oncologist 2000;5:1-7.
5.	Rodgers GM, Becker PS, Blinder M, Cella D, Chanan-Khan A, Cleeland C, et al. Cancer-and chemotherapy-induced anemia. J Natl Compr Canc Netw 2012;10:628-53.
6.	Bach V, Schruckmayer G, Sam I, Kemmler G, Stauder R. Prevalence and possible causes of anemia in the elderly: A cross-sectional analysis of a large European university hospital cohort. Clin Interv Aging 2014;9:1187-96.
7.	Merlini L, Cartenì G, Iacobelli S, Stelitano C, Airoldi M, Balcke P, et al. Anemia prevalence and treatment practice in patients with non-myeloid tumors receiving chemotherapy. Cancer Manag Res 2013;5:205-14.
8.	Prabhash K, Nag S, Patil S, Parikh PM. Optimising management of cancer related anemia. Indian J Cancer 2011;48:1-10. [PUBMED] [Full text]
9.	Vijayaraghavan K, Brahmam GN, Nair KM, Akbar D, Rao NP. Evaluation of national nutritional anemia prophylaxis programme. Indian J Pediatr. 1990;57:183-90..
10.	Peyrin-Biroulet L, Williet N, Cacoub P. Guidelines on the diagnosis and treatment of iron deficiency across indications: A systematic review. Am J Clin Nutr 2015;102:1585-94.
11.	Dignass A, Farrag K, Stein J. Limitations of serum ferritin in diagnosing iron deficiency in inflammatory conditions. Int J Chronic Dis 2018;2018:9394060.
12.	Snow CF. Laboratory diagnosis of vitamin B12 and folate deficiency: A guide for the primary care physician. Arch Intern Med 1999;159:1289-98.
13.	Ludwig H, Van Belle S, Barrett-Lee P, Birgegård G, Bokemeyer C, Gascón P, et al. The European Cancer Anaemia Survey (ECAS): A large, multinational, prospective survey defining the prevalence, incidence, and treatment of anaemia in cancer patients. Eur J Cancer 2004;40:2293-306.
14.	Rizzo JD, Lichtin AE, Woolf SH, Seidenfeld J, Bennett CL, Cella D, et al. Use of epoetin in patients with cancer: Evidence-based clinical practice guidelines of the American Society of Clinical Oncology and the American Society of Hematology. J Clin Oncol 2002;20:4083-107.
15.	Trotti A, Byhardt R, Stetz J, Gwede C, Corn B, Fu K, et al. Common toxicity criteria: version 2.0. an improved reference for grading the acute effects of cancer treatment: impact on radiotherapy. Int J Radiat Oncol Biol Phys 2000;47:13-47.
16.	World Health Organization. Worldwide Prevalence of Anaemia 1993-2005: WHO Global Database on Anaemia. Geneva: World Health Organization, 2008. Available at https://apps.who.int/iris/bitstream/handle/10665/43894/9789241596657_eng.pdf. Last assessed on 30th October 2020.
17.	Kumari R, Bharti RK, Singh K, Sinha A, Kumar S, Saran A, et al. Prevalence of iron deficiency and iron deficiency anaemia in adolescent girls in a tertiary care hospital. J Clin Diagn Res 2017;11:BC04-6.
18.	Baburao A, Narayanswamy H. Clinico-pathological profile and haematological abnormalities associated with lung cancer in Bangalore, India. Asian Pac J Cancer Prev 2016;16:8235-8.
19.	Ghosh J, Singh RK, Saxena R, Gupta R, Vivekanandan S, Sreenivas V, et al. Prevalence and aetiology of anaemia in lymphoid malignancies. Natl Med J India 2013; 26:79-81.
20.	Pandey A, Singh A, Singh S, Kumar A. Patient-doctor ratio across nine super speciality clinics in government hospital: A cross sectional study. Int J Community Med Public Health 2019;6:4421-5.
21.	Pandey A, Singh A, Singh S. Prevalence of Vitamin D deficiency in treatment-naive individual consecutive cancer patients. Cancer Res Stat Treat 2020;3:25-31. [Full text]
22.	Pandey A. Author reply to Shamsi et al. and Vora. Cancer Research, Statistics and Treatment. 2020;3:372.
23.	Pandey A, Ahlawat S, Singh A, Singh S, Murari K, Aryan R. Outcomes and impact of minimal residual disease (MRD) in pediatric, adolescent and young adults (AYA) with acute lymphoblastic leukemia treated with modified MCP 841 protocol. Cancer Res Stat Treat 2020;3:183-91. [Full text]
24.	Pandey A, Deshpande P, Singh A, Singh S, Murari K, Aryan R. Oral Prednisolone, Etoposide, 6-Mercaptopurine (PREM) metronomic chemotherapy in treatment naïve and partially treated acute myeloid leukemia in a resource constrained setting. Cancer Res Stat Treat 2020;3:172-82. [Full text]
25.	PandeyA, Raj S, Madhawi R, Devi S, Singh RK. Cancer trends in Eastern India: Retrospective hospital-based cancer registry data analysis. South Asian J Cancer 2019;8:215-7.
26.	Pandey A, Singh A, Singh S, Shahi H, Kumar A, Kumari A, et al. First physician of contact and time to presentation among rural adult cancer patients: A prospective survey. South Asian J Cancer 2020;10.4013.
27.	Theurl I, Mattle V, Seifert M, Mariani M, Marth C, Weiss G. Dysregulated monocyte iron homeostasis and erythropoietin formation in patients with anaemia of chronic disease. Blood 2006;107:4142-8.
28.	Weiss G, Goodnough LT. Anemia of chronic disease. N Engl J Med 2005;352:1011-23.
29.	Punnonen K, Irjala K, Rajamaäki A. Serum transferrin receptor and its ratio to serum ferritin in the diagnosis of iron deficiency. Blood 1997;89:1052-7.