A reduced number of lymphocytes — one of the main types of immune cells — in advanced ovarian cancer patients before treatment is linked with a higher risk of disease worsening and shorter overall survival, according to a South Korean study.

The study, “Pretreatment lymphocytopenia is an adverse prognostic biomarker in advanced‐stage ovarian cancer,” was published in the journal Cancer Medicine.

Lymphocytes, which mostly include T-cells and B-cells, play a key role in the fight against foreign substances and external threats. That’s why a patient’s immune response often is measured by the amount of these cells in circulation.

Research suggests that lymphocytopenia (a lower-than-normal number of lymphocytes in the blood) before surgery is an independent prognostic factor in several cancers, including kidney, bladder, and colorectal cancers. But it is not known if the same is true for ovarian cancer.

Aiming to address that, a team of Korean researchers examined data from 506 advanced ovarian cancer patients, followed from 2006 to 2017 at the Yonsei Cancer Hospital, Seoul, South Korea.

Patients were divided into two groups: those who had been treated with neoadjuvant (pre-surgery) chemotherapy (247 patients), and those who had been submitted to debulking surgery (a survival intervention to remove as much of the tumor as possible) followed by chemotherapy (259 patients).

The researchers started by establishing the optimal cutoff value of lymphocyte count — 1,490 million per liter of blood — to differentiate the patients with lymphocytopenia prior to treatment from those with normal lymphocyte counts.

Using this value, 60.7% of patients in the neoadjuvant chemotherapy group, and 66.4% of those in the surgery group, were diagnosed with lymphocytopenia.

Researchers then compared the time patients with and without lymphocytopenia lived without their disease worsening — a measure called progression-free survival — as well as their survival rates.

In the neoadjuvant chemotherapy group, those with initial lymphocytopenia had worse progression-free survival (16.3 months versus 20.2 months) and overall survival (45.6 months versus 89.2 months).

The worse survival outcomes also were seen among lymphocytopenia patients in the surgery group. These patients lived a median of 17 months without their disease worsening and survived for 52.6 months, compared to 29 months and 82 months for those without lymphocytopenia.

For both groups, lymphocytopenia was deemed an independent risk factor associated with a higher risk of disease progression and lower overall survival. When lymphocyte count was seen as a continuous variable, it remained an adverse factor for both groups, “demonstrating that the magnitude of lymphocytopenia correlates with an inferior survival outcome,” researchers explained.

Researchers hypothesize that lymphocytopenia could reflect a state of immune suppression that will reduce the effect of chemotherapy. They believe that “therapeutic strategies directed toward the restoration of antitumor immunity may improve the outcome.”