Is Serum PSA a Reliable Indicator to Omit Skeletal Scintigraphy Among Newly Diagnosed Prostate Cancer Patients?

Abstract

Objectives: Skeletal scintigraphy is most sensitive modality for detection of bone metastases in prostate cancer (PCa). Bone scintigraphy (BS) is currently not recommended for staging of PCa patients with serum prostate specific antigen (S.PSA) <10 ng/ml or in low-risk group (NCCN 2021, EAU-EANM-2020). This study aims to establish cutoff of S.PSA levels to predict metastatic bone disease in newly diagnosed treatment naive patients with carcinoma Prostate, in Uttarakhand region, India. Materials and Methods: We retrospectively reviewed 105 treatment naïve PCa patients referred to Nuclear Medicine Department, All India Institute of Medical Sciences, Rishikesh, for BS. We assessed association between S.PSA levels (performed within 6 weeks of imaging), Gleason Score (GS)/International Society of Urological Pathology (ISUP) grading and metastatic disease diagnosed on BS. Results: A total of 105 patients were included in this study with an average age of 69 ± 9.4 years (42–87 years). Out of 105 patients, 62 (59%) were positive and 43 (41%) patients were negative on BS for skeletal metastasis. According to S.PSA levels, patients were divided into five subgroups. On subgroup analysis, most of the patients with S.PSA of >100 were positive for metastasis on BS (83.7%) but a significant number of patients with S.PSA<10 were also positive for skeletal metastasis (46%–7/15) on BS. Conclusion: In current patient population, a high incidence of bone metastasis is noted even at low S.PSA levels and in low-risk groups. Hence, BS can be considered in carcinoma prostate patients even with PSA levels <10 ng/ml. Although, other parameters such as GS/ISUP grading, pathological grade and clinical stage should also be considered and individualised risk adapted strategy to be followed for initial staging.