Early detection of second primary solid tumors in patients with an index solid malignancy.

Abstract

e13792 Background: Multiple primary malignant neoplasms (MPMN) are defined as two or more independent malignant tumors with distinct histopathology arising in different organs or tissues. This study aims to analyze the early detection of second primary solid tumors in patients followed after an index solid malignancy. Methods: A retrospective study included 513 patients with solid tumors who developed a second primary solid malignancy treated at the Henry Moore Oncology Institute (October 2012 to August 2025). Patients with index tumors stage I-III were selected. Second tumors were classified as synchronous (≤6 months) or metachronous ( > 6 months). Detection was categorized as screening-based or symptomatic. Age, sex, carcinogen exposure, and genetic factors were evaluated. Results: Among 513 patients, 464 (90%) had an index tumor stage I-II. Median age at first tumor was 60 years (r = 16-88); 240 were women. Most frequent index tumors were breast (n = 136), colorectal (n = 80), prostate (n = 67), and renal (n = 36). Median follow-up was 61 months (r = 0-123). Second tumors were synchronous in 100 and metachronous in 364 patients, with a median interval of 55 months (r = 7-111). Overall, 332 second tumors were considered preventable and detected by screening, while 132 were non-preventable. Preventable tumors were significantly more frequently diagnosed at early stages (p < 0.001). Conclusions: This is the largest reported cohort of patients with second primary solid tumors in Argentina. Most index tumors were diagnosed at early stages. The majority of preventable second tumors were detected at early stages, supporting the role of effective treatments, structured follow-up, and modern imaging in improving early detection, curative potential, and survival Stage distribution of second primary tumors according to preventability. Tumor site Non-preventable Preventable Stage 0 I II III IV Total Breast 0 76 11 30 23 6 6 76 Colorectal 0 75 3 5 20 33 14 75 Prostate 0 62 2 24 24 5 7 62 Lung 0 54 2 8 5 15 24 54 Renal 51 0 4 37 4 4 2 51 Others 81 65 14 47 20 20 40 146 Total 132 332 36 151 96 88 93 464