Cancer surveillance in the Amazon region is limited and population-level data for the Ecuadorian Amazon are sparse. This study used registry data to analyse temporal trends in cancer incidence between 1990 and 2019 among residents of four Amazonian provinces, identify the most prevalent cancer types, and describe provincial and temporal distribution.
This was a retrospective, registry-based ecological analysis. The unit of analysis was aggregated cancer incidence by province, sex, age group, and five-year study period. All analyses used cases recorded in the Quito Population-Based Cancer Registry for the period 1990–2019. Age- and sex-standardised rates were calculated using Segi’s world standard population.
The study included patients whose habitual residence was in the Ecuadorian Amazon provinces of Sucumbíos, Orellana, Napo, and Pastaza and who were diagnosed with cancer between 1990 and 2019. INEC population projections were used for denominators. The combined population of the four provinces was estimated at approximately 627,195 (2023 estimate), with demographic shifts during the study showing an aging population and a reduced proportion under 25 years of age.
The Quito Population-Based Cancer Registry provided the data. The registry records all new cancer diagnoses made in Quito and includes cases whose habitual residence is outside Quito. Sources include histopathology reports, oncology clinical records, hospital discharge data, and mortality records. The registry follows IARC/IACR standards. The Amazon provinces do not have provincial histopathology services or organized cancer prevention programmes, so case ascertainment depends on referrals to Quito and patients’ ability to access diagnostic services.
Analyses were structured into six consecutive five-year periods (1990–1994 through 2015–2019). Incidence rates were calculated using population projections stratified by sex and five-year age groups; age-standardisation used the direct method with Segi’s world population. Temporal trends were assessed with quasi-Poisson regression models adjusted for age group and sex, using the log population as an offset to account for overdispersion. Incidence rate ratios (IRRs) with 95% confidence intervals were estimated for period effects.
Between 1990 and 2019 the registry recorded 5,008 cancer cases among residents of the four provinces. After excluding 127 cases with missing age or province, 4,881 cases were analysed; 36.8% were men. The number of recorded cases increased progressively across the study periods, with a reported 357% increase from 1990–1994 to 2015–2019. Both sexes showed similar overall percentage increases, though variation in timing of sharper rises differed between men and women across specific periods.
Age-standardised incidence rates for the combined region rose markedly over the study. In men the rate increased from 19 per 100,000 in 1990–1994 to 50 per 100,000 in 2015–2019 (a 163.2% increase). In women the rate rose from 37 to 96 per 100,000 (a 159.5% increase). Provincial patterns varied: recent increases were more pronounced in Pastaza, Napo, and Sucumbíos among women, and in Napo and Orellana among men.
For 2015–2019, the five most frequent cancers (with age-standardised rates per 100,000) included, in men: prostate cancer (8.3), stomach (5.4), and non-melanoma skin (4.9). In women the leading cancers were invasive cervical cancer (18.2), breast cancer (13.6), and thyroid cancer (11.8). Across the whole study period the four most frequent cancers accounted for roughly 40% of male cases and 60% of female cases. Temporal patterns showed declining stomach and cervical cancers but increasing prostate, breast, and thyroid cancers.
Quasi-Poisson regression adjusted for age and sex estimated an overall increase in cancer incidence of 22.8% per 5-year period (IRR 1.23, 95% CI 1.20–1.25). Incidence was higher in women than men overall (IRR 2.00, 95% CI 1.88–2.14). A sex-by-period interaction indicated a faster increase in women (≈24.7% per 5-year period) than in men (≈19.7% per 5-year period).
The analysis documents a clear rise in recorded cancer burden in the studied Amazon provinces over three decades, with marked increases in age-standardised incidence rates and case counts. The pattern of most frequent cancers differs by sex: prostate, stomach and skin cancers in men; cervical, breast and thyroid cancers in women. The increases observed may reflect several non-mutually exclusive factors: demographic ageing, improved registration and access to diagnostic services in Quito, and potential real increases in incidence. The lack of provincial histopathology and oncologic treatment services and the absence of organised regional prevention programmes are important contextual limitations that likely affect both true incidence and case ascertainment.
The authors emphasise the need to strengthen local healthcare infrastructure and cancer registry systems and to implement targeted prevention and early detection programmes adapted to the region’s specific epidemiology and access constraints.
The study used anonymized registry data and received ethical approval from the SOLCA Quito Research Ethical Committee (reference OBS.23.216). Data underlying the study are available from the National Cancer Registry from Ecuador as reported by the authors. The authors declared no specific funding and no competing interests.
Limitations noted include dependence on cases diagnosed in Quito with potential under-ascertainment and differential reporting across provinces and time, and missing data for a subset of recorded cases. Within these constraints, the study documents a substantial rise in recorded cancer incidence from 1990 to 2019 in the Ecuadorian Amazon and calls for enhanced cancer control capacity, improved registry coverage, and tailored prevention and early detection strategies for the region.