A Descriptive Study of the Types and Survival Patterns of Saudi Patients with Multiple Primary Solid Malignancies: A 30-Year Tertiary Care Center Experience

Abstract

Background and objective: Cancer survival has improved significantly, which reflects the achievements in screening, diagnosis, and treatment. As a consequence, multiple primary malignancies are diagnosed more frequently, with an incidence ranging from 0.52-11.7%. The types of malignancy that coexist and survival patterns vary notably in different countries and geographical areas. Due to the limited literature in Saudi Arabia, a baseline of prevalent malignancy combinations and their survival patterns would support early detection and disease management.

Method: This was a retrospective descriptive study conducted from 1993-2022 at King Abdulaziz Medical City, Department of Medical Oncology, Riyadh, Saudi Arabia. Patients with at least two biopsy-proven solid malignancies were included. Patients with hematological malignancies, missing data, or an uncertain or indecisive pathology report were excluded.

Result: In total, 321 patients were analyzed. More than half (57.3%) of the patients were female. A third (33%) of the cases were synchronous, and 67% were metachronous. The most frequent site of the first primary malignancy was breast cancer, followed by colorectal, skin, and thyroid cancers. The most frequent site of the second primary malignancy was colorectal cancer, followed by thyroid, breast, and liver cancers. Only 4% of the cases had a third primary malignancy, with colorectal and appendiceal cancers being the most frequent. The most frequently observed histopathology in the synchronous and metachronous malignancies was adenocarcinoma. Breast-colorectal, breast-thyroid, and kidney-colorectal were the most frequently observed malignancy combinations.

Conclusion: The current study offers a baseline of multiple primary malignancies in Saudi Arabia and provides supporting evidence that the pattern of multiple primary malignancies varies among different countries and ethnicities. The possibility of developing another primary malignancy should be considered when treating and monitoring cancer patients.

Keywords: metachronous malignancies; multiple primaries; multiple primary malignancies; second primary; synchronous malignancies.

Figure 1

Shows a chart showing the details of the excluded patients. A total of 129 patients were excluded from the analysis, 29 of whom were non-Saudi, 97 with hematological malignancies, and 3 had no or uncertain pathology reports.

Figure 2

An alluvial plot showing stages of first and second primary malignancies. Detailed description: A total of 10.9% of the patients had their first primary malignancy diagnosis when it already metastasized to a distant organ, 21.8% had regional metastasis, and the rest had localized disease. A total of 16.8% of the patients had metastatic disease when diagnosed, 17.8% had regional metastasis, and the rest had localized disease.

Figure 3

Shows the most frequent site of the first and second primary malignancies. Breast cancer was the most common first primary diagnosis, followed by colorectal and skin cancers. Colorectal cancer was the most frequent second primary diagnosis, followed by thyroid and breast cancers.

Figure 4

Shows the most frequent histopathologic morphology of the first and second primary malignancies. Adenocarcinoma was the most common first primary histopathology, followed by infiltrating ductal carcinoma and squamous cell carcinoma. Adenocarcinoma was also the most common second primary histopathology, followed by papillary carcinoma and ductal carcinoma.

Figure 5

An alluvial plot showing the most frequent malignancy combinations. The most frequent malignancy combinations were breast–colorectal, breast–thyroid, kidney–colorectal, and colorectal–breast. Further frequent malignancy combinations are provided in Table 3.

Figure 6

Shows the difference in survival of patients with synchronous and metachronous malignancies. The median survival time was 9.2 ± 1.7 and 13.2 ± 1.2 years for synchronous and metachronous malignancies, respectively, and the difference was statistically significant (p = 0.002).

Figure 7

Shows the difference in survival based on patients’ gender. The median survival time in the males was 11.7 ± 1.0 years, and in the females, 11.9 ± 1.1 years, with no significant difference (p = 0.928).

Figure 8

(A,B) shows the difference in survival when classified based on the MPM category by gender. The median survival time was 10 ± 1.7 and 12.1 ± 1.6 years for synchronous and metachronous malignancies, respectively, in the males, and in the females, the median survival time was 7.4 ± 2.6 and 13.5 ± 1.3 years for synchronous and metachronous malignancies, respectively. A significant difference was detected with the log-rank test (p = 0.002).