Correlation of PET Scan Negativity and Higher Absolute Lymphocytes: Monocytes (ALC:AMC) Ratio As Prognostic Markers in Classical Hodgkin Lymphoma Patients Treated with ABVD Chemothearapy at a Single Center in Saudi Arabia

The International Prognostic Score (IPS) is the standard stratification system for survival in patients with classical Hodgkin's lymphoma (cHL). However, the IPS only applies to patients with advanced stage disease and it does not offer risk stratification for classical Hodgkin's lymphoma patients diagnosed with limited disease [i.e., stages I and IIA, without constitutional symptoms and no bulky disease. Furthermore, early interim positron emission tomography (PET) has been shown to have a prognostic value superior to that of the IPS in patients with advanced-stage cHL in an analysis (Gallamini et al).

Lymphopenia (<600/ul), monocytosis >750 per ul (Tadmore et al) and high tumor-associated macrophages (TAM) are reported to be negative prognostic factors for survival in classical Hodgkin's lymphoma (Koh et al). More recent studies suggested a prognostic role for the peripheral blood absolute lymphocyte count/absolute monocyte count (ALC/AMC) ratio at diagnosis in cHL patients treated with multitude of chemotherapies (Porrata et al, Tadmor et al). It is intriguing to investigate the significance of the ALC/AMC ratio in relation to PET negativity after treatment.

Out of 164 cases of cHL treated at our center with ABVD +/- radiation therapy, we identified 70 patients who were evaluated by PET Scan. Median age was 26 years (range 14-80), 33 (47%) were stage IV, Median IPS was 3 (range1-6). We tested correlation of a high ALC/AMC ratio (>2.1) with achievement of a negative PET scan after ABVD chemotherapy. We arbitrarily chose cut-off value of >2.1 (Tadmore et al) from the multiple values reported recently, as this multicenter study had the largest number of patients.

A total of 45 patients achieved a negative PET scan. Mean ALC/AMC ratio was 2.39 (range0.19-14.6). ALC/AMC ratio of >2.1 did show a trend for better OS in addition to a negative PET scan. A Spearman correlation test of a negative PET result showed a positive correlation with ALC/AMC ratio of >2.1 though it was weak.

This study suggests that the ALC/AMC ratio may be a simple, inexpensive, and independent prognostic factor in cHL outcome and may have a role in the stratification of cHL patients in addition to the International Prognostic Score, TAM content and acheivement of a negative PET scan early post chemotherapy. However we plan to define our own best cut off value for ALC/AMC ratio by ROC and AUC analysis as ALC/AMC Ratio of ≥2.1 did not discriminate survival advantage very well and it may be a reason for weaker correlation with likelihood of a negative PET.

Further larger studies are needed to confirm our findings.