**Background:** Cancer is a growing public health problem in sub-Saharan Africa (SSA), with age-standardised incidence and mortality rates of 128.2 and 87.2 per 100,000 people, respectively. Late presentation and delays in diagnosis and treatment consistently translate into poor outcomes. The region faces system-level challenges including limited healthcare financing, inadequate infrastructure, and a dual burden of infectious and non-communicable diseases. Fragmented pathways of care, dependence on external funding, and lack of coordination across primary, secondary, and tertiary sectors contribute to critical delays. This systematic review aimed to collate and appraise factors influencing diagnostic and treatment delays of adult solid tumours in SSA using the 'Three Delays' framework (seeking care, reaching care, receiving quality care).
**Methods:** A systematic review was conducted following PRISMA guidelines. PubMed and Embase were searched for articles published between January 1995 and March 2021. Inclusion criteria were quantitative or mixed-method research in English on solid cancers in SSA countries. Exclusion criteria included paediatric populations, haematologic malignancies, and studies of public perceptions without a cancer diagnosis. Two reviewers screened abstracts and full texts, with a third reviewer resolving conflicts. Data extraction included year, country, demographics, disease subsite, study design, type of delay, reasons for delay, and primary outcomes. Quality assessment was performed using the ROBINS-E tool.
**Key Results:** From 6,391 initial articles, 193 underwent full-text review and 57 studies were included. 40% were from Nigeria (26%) or Ethiopia (14%). 70% focused on breast (53%) or cervical (18%) cancer. Two-thirds used cross-sectional designs; 23% were retrospective and 11% prospective. 43 studies had a high risk of bias at preliminary stages; all 14 studies meeting criteria for full assessment had high or very high risk of bias. Key reasons for delays included: (1) Seeking care: lack of awareness, fear, belief in witchcraft, preference for traditional healers, financial incapability, and prioritising daily survival; (2) Reaching care: physical distance, transport costs, misdiagnosis at primary level, lack of referral coordination, and being told by healthcare workers the condition was incurable; (3) Receiving quality care: high out-of-pocket costs, chemotherapy stock-outs, few specialists, lack of multidisciplinary care, poor infrastructure, power outages, and demotivated staff. Across all delays, cost was a major factor, with patients requiring cover for transport, accommodation, diagnostic tests, and medicines.
**Clinical Implications:** The review demonstrates a very limited evidence base despite the importance of this subject, with research clustered to a few countries and tumour types. Major causes of cancer mortality in SSA such as prostate and oesophageal cancer were not addressed. The findings suggest that interventions must address the complex interaction of economic, psychological, sociocultural, geographic, and health service factors. To reduce cancer mortality, health systems need to address delays across the entire cancer pathway, provide holistic support for patients and the workforce, and build resilient cancer control programmes based on locally generated evidence. The authors call for more robust research using appropriate study designs to inform policy, as current evidence is dominated by cross-sectional surveys that fail to account for confounding factors and system-level processes.