**Background:** Cancer is a leading cause of death worldwide, and early diagnosis improves outcomes. Platelets play an active role in cancer progression through inflammation, angiogenesis, and metastasis. Mean Platelet Volume (MPV) is a non-invasive, low-cost marker of platelet activation routinely available from complete blood counts. This systematic review aimed to investigate MPV alterations across multiple cancer types and assess its relationship with diagnosis, disease severity, survival, and treatment outcomes.
**Methods:** A literature search was conducted in PubMed and Google Scholar for studies published between January 2010 and December 2022. The review was registered in PROSPERO (ID CRD42023396237). Search terms included MPV, platelet activation, and cancer-related keywords. Inclusion criteria were: English-language studies measuring MPV in 12 specified cancer types. Exclusion criteria included animal studies, case reports, studies with only metastatic patients, cancer survivors, mixed cancer types, ratios/algorithms including MPV, post-treatment MPV changes, patients with comorbidities, and pediatric/adolescent populations. Quality assessment was performed using the Newcastle-Ottawa Scale for cohort and case-control studies and the AXIS tool for cross-sectional studies, conducted independently by two researchers. Four independent researchers extracted data on MPV alterations and survival outcomes.
**Key Results:** From 3800 PubMed articles and 17,500 Google Scholar articles screened, 83 studies with 21,034 participants across 12 cancer types were included. Most studies were conducted in China and Turkey with retrospective designs. For gastric cancer (8 studies, 1061 patients), most found elevated MPV in patients versus controls, and surgery reduced MPV. For colon cancer (11 studies, 3463 patients), results were mixed: one study showed increased MPV, one showed decreased MPV, and 4 of 6 studies found that reduced MPV was associated with increased survival. For esophageal squamous cell carcinoma (5 studies, 4258 patients), two studies found increased MPV and one found decreased MPV in patients. For renal cell carcinoma (3 studies, 681 patients), all found significantly reduced MPV in patients, with low MPV predicting shorter survival. For breast cancer (8 studies, 1485 patients), elevated MPV was consistently found in patients and associated with metastasis and worse outcomes. For ovarian cancer (6 studies, 906 patients), results were mixed. For endometrial cancer (8 studies, 1707 patients), all studies with control groups found increased MPV in cancer patients. For thyroid cancer (10 studies, 1305 patients), most found higher MPV in patients. For lung cancer (15 studies, 3754 patients), patients had higher MPV than controls, and 4 of 10 studies found higher MPV related to lower survival. For bladder cancer (5 studies, 879 patients), results were mixed. For gallbladder cancer (3 studies, 473 patients), lower MPV was found in patients. For multiple myeloma (1 study, 62 patients), low MPV was associated with significantly decreased survival.
**Clinical Implications:** MPV alterations in cancer reflect cancer-related inflammation. Proinflammatory cytokines (IL-1, IL-3, IL-6) promote megakaryocyte proliferation and increase large platelet presence. Activated platelets facilitate cancer progression through VEGF secretion, angiogenesis, tumor cell dissemination, and immune evasion. MPV could serve as a potential biomarker for cancer diagnosis and treatment optimization. However, preanalytical factors (anticoagulant type, temperature, time to analysis), lack of standardized reference values, and confounding factors (age, gender, lifestyle, comorbidities) limit current clinical applicability. The review's limitations include predominance of retrospective studies, small sample sizes, geographic concentration in China and Turkey, and heterogeneity in cut-off values and control group definitions. Further prospective studies with standardized methodologies are needed to establish MPV's exact role in cancer management.