This is a 70 year old newly diagnosed metastatic prostate cancer patient. He has past history of minor stroke in which he fully recovered. On family history, his sister had history of DCIS breast in her 50s
He presented with nocturia and bone pain in November 2018. His PSA was 29 (12/2018). TRUS biopsy of prostate confirmed adenocarcinoma GS (5+4), 11/12 core +ve in 12/2018. Staging PSMA PET/CT scan was performed in 1/2019 showing diffuse prostate uptake and pelvic and para-aortic lymph node metastasis. No bone metastasis was found.
He was given upfront abiraterone + LHRHa afterwards with initially response from January to November 2019. His PSA rebounded afterwards. Biochemical-free progression free survival was 10 months only (1-11/2019). Reassessment PETCT in 12/2019 confirmed progression of pelvic lymph nodes. He lost more than 20 kg of weight within two months and developed severe right leg lymphoedema and haematuria.
Next generation sequencing (NGS) on his primary tumour tissue was arranged. While waiting the NGS result, one cycle of docetaxel was given but there was no PSA response and patient tolerated poorly. Bone scan in 2/2020 found pelvic bone metastases. NGS result showed MSI-high and high tumour mutation burden (73 Muts/Mb). Additionally, multiple mutations were detected including APC, ATM, MSH3, MSH6, PMS2, PTCH1 and PTEN mutations.
In view of MSI-H and TMB-high, he was prescribed pembrolizumab 200mg every 3 weeks (fixed dose). His PSA was 28 (2/2020) before pembrolizumab. After 3 cycles of pembrolizumab, his PSA dropped to below <0.1 (5/2020) and his lymphoedema and haematuria resolved completely. Reassessment PSMA PETCT (6/2020) showed almost complete metabolic and radiological response except mild diffuse low grade activity in shrunken-size prostate. Consolidation radiotherapy to prostate was given (55Gy/20Fr)
Further germ line testing showed no evidence of Lynch syndrome (no MLH1, MSH2, MSH6, PMS2 mutations). In addition, no germ line mutations (including APC, ATM, BRCA1, BRCA2, CDH1, CDK4, CDKN2A, CHEK2) were found.