The pattern of osseous vs. visceral metastasis in carcinoma prostate in North Indian population: Light at the end of the tunnel

Introduction: Prostate cancer is the second most common cause of cancer and the sixth leading cause of cancer death among men worldwide. According to published literature, in a significant number of patients, 80-90% develop bone metastasis, nearly 36% develop lymph node metastasis, and 20-30% develop visceral metastasis. ⁶⁸Ga-PSMA PET/CT is an established modality of choice to assess disease burden in metastatic disease and guide the selection of patients for treatment with PRRT. Visceral metastasis is associated with poor outcomes in patients treated with PRRT. Liver metastasis has the worst prognosis when compared to other anatomic sites. Thus, the present study aimed to evaluate the pattern of metastasis in adenocarcinoma prostate using ⁶⁸Ga-PSMA PET/CT.

Methods: This is a retrospective study done in a tertiary care hospital in North India. Four hundred seventeen patients were included in the study who were referred to us for ⁶⁸Ga-PSMA PET/CT for staging and restaging of patients with biopsy proven adenocarcinoma prostate. All nonmetastatic patients with localized disease confined to the prostate were excluded from the analysis. Ninety-five patients showed disease confined to the prostate or prostatic bed on ⁶⁸Ga-PSMA PET/CT and hence were excluded from the study. Age and S.PSA were extracted from the database. Sites of metastasis on ⁶⁸Ga-PSMA PET/CT were divided into the following anatomic site: regional (pelvis) lymph node, metastatic lymph node (retroperitoneal and others), bone, lung, liver, and other sites. Data were entered using Microsoft Excel, and statistical analysis was performed using SPSS version 25.

Results: A total of 322 patients were included in the study, which showed metastasis in at least one anatomic site. The mean age of the patient was 67 years. The mean S.PSA level was 188 ng/ml. The most common site of the metastasis was osseous, which was seen in 260 patients (81%). Regional pelvis and nonregional lymph node metastases were noted in 226 (70%) and 182 patients (56%). Among visceral metastasis, lung and liver involvement were seen in 52 (16%) and 23 (7%), respectively. Seven patients showed metastasis to other sites, including breast, muscle, mesentery, omentum, adrenal, spleen, and meninges.

Conclusions: ⁶⁸Ga-PSMA PET/CT evaluated metastatic burden in 322 patients. We found that these patients have frequent metastases to bone, regional, and nonregional lymph nodes. A regional MRI with a bone scan may not suffice for staging or restaging these patients. It highlights the need for whole-body imaging to evaluate metastatic burden in Indian patients with high S PSA. From the clinical perspective, the short implications of the data are that the incidence of visceral metastases (lung and liver) is less frequent in the North Indian population. Hence there is a likelihood of a better outcome of PRRT in the same population.