A recent analysis of records of more than 33 lakh patients has shown an association of increased platelet count with an increased risk of cancer for at least 2 years.

The retrospective study, published in JAMA Network Open, included 3,386,716 residents of Ontario, Canada with a recorded routine CBC test result from January 1, 2007, to December 31, 2017, with follow-up until December 31, 2018. The study subjects had a normal platelet count in the previous two years and no history of cancer.

Of the 3,386,716 subjects, 53,339 (1.6%), mean age 59.7 years, had thrombocytosis (platelet count >450 x 10⁹/L) and a previous normal platelet count; 70% of the individuals with thrombocytosis were women.

Around 5.5% of those with thrombocytosis were diagnosed with a solid cancer in the 2-year follow-up period, while 7.5% were diagnosed with cancer within 5 years.

Compared to patients with normal platelet counts, the association between thrombocytosis and cancer was found to be highest for cancer of the ovary with a relative risk of 7.11. The relative risks for cancer of the stomach were 5.53, colon (RR 5.41), lung (RR 4.41), kidney (RR 3.64) and esophagus (RR 3.64). These cancers are usually asymptomatic; hence, they are often diagnosed at an advanced stage.

This study has shown a statistically significant association of thrombocytosis with an increased risk of cancer among individuals with normal platelet levels in the preceding 2 years. Most solid cancers were diagnosed within the first 2 years after the date of the first CBC test.

According to the authors, thrombocytosis may be a clinical marker for the presence of an existing cancer, which leads to thrombocytosis. Therefore, they suggest that individuals with new unexplained thrombocytosis should be offered screening for several common cancers.

Reference

1. Giannakeas V, et al. Incidence of cancer among adults with thrombocytosis in Ontario, Canada. JAMA Netw Open. 2021 Aug 2;4(8):e2120633.