Rare cancer incidence and mortality trends among older adults in Martinique: a population-based registry study, 2008-2022

Background Rare cancers account for approximately 25% of all cancer diagnoses worldwide, and around 50% of cancer cases occur in people aged ≥ 65 years. However, both groups remain systematically underrepresented in epidemiological research, particularly in the Caribbean region. Methods We conducted a population-based cohort study (2008–2022) using data from the Martinique Cancer Registry and French National Mortality Database. Age-standardized incidence and mortality rates (ASIR and ASMR) were estimated using the Segi-Doll World standard population, and Annual Average Percent Change (AAPC) with 95% confidence intervals were calculated for patients aged ≥ 65 years by tumor site and sex. Findings Between 2008 and 2022, 778 older adults were diagnosed with rare cancers in Martinique (61% men), with 442 deaths recorded (64.5% men). Overall incidence and mortality showed no statistically significant trends in either sex (men: AAPC for mortality was + 0.23%, 95% CI -2.46 to 2.99, p = 0.869 and, in women: AAPC − 2.29%, 95% CI -5.79 to 1.34, p = 0.213). The only statistically significant trend was rising gallbladder cancer mortality in men (AAPC + 10.35%; 95% CI 1.99–19.38; p = 0.014), with ASMR increasing from 2.8 to 11.0 per 100,000 person-years. The incidence of laryngeal cancer in men showed a borderline increasing trend (AAPC + 5.46%; p = 0.075). The mortality burden was predominant in men for laryngeal cancer (86.1%), melanoma of the skin (81.8%), and esophageal cancer (77.6%), and increased progressively with age, reaching an ASMR of 96.0 per 100,000 person-years in men aged 85 years. Interpretation Rare cancer patterns in older adults in Martinique reflect tumor biology, demographic aging, and structural healthcare constraints. The rising gallbladder cancer mortality in older men underscores critical gaps in hepatobiliary imaging access and timely oncological referral. Strengthening population-based registries and regional data-sharing networks is essential to inform evidence-based rare cancer control across the Caribbean.