Emerging research suggests that doubling of total tumor volume (PSMA-TV) and total lesion uptake (TL-PSMA) on prostate-specific membrane antigen positron emission tomography/computed tomography (PSMA PET/CT) are associated with higher risks in metastatic castration-resistant prostate cancer (mCRPC).
For the retrospective study, recently published in European Radiology, researchers examined the impact of key parameters on (18F)PSMA-1007 PET/CT on overall survival (OS) in 60 patients with mCRPC. In addition to baseline PET/CT exams performed prior to treatment with androgen receptor-targeted agents (ARTAs) or chemotherapy, all patients had follow-up PET/CT scans after three to four months of treatment, according to the study.
The researchers found that doubling of PSMA-TV and TL-PSMA were associated with a 41 percent and 40 percent higher likelihood, respectively, of lower OS. Additionally, for every 10 cm increase in DmaxVox (defined as the distance between two lesions furthest apart), the study authors noted a 31 percent higher likelihood of lower OS.
The study authors also noted that all of the aforementioned parameters were independently prognostic for OS regardless of PSA level and line of treatment.
“The results of this study showed that baseline PSMA PET/CT scans provide prognostic information for mCRPC patients treated with ARTA or chemotherapy. For each patient, it is important to weigh the expected treatment benefit against the risk of toxicity and associated costs,” wrote lead study author Fleur Kleiburg, M.D., who is associated with the Department of Radiology and the Section of Nuclear Medicine at Leiden University Medical Center in Leiden, the Netherlands, and colleagues.
In the absence of software to facilitate automated segmentation of prostate tumors in patients with mCRPC, the researchers suggested that the DmaxVox parameter measurement could be a viable prognostic alternative.
“Especially since (tumor) segmentations to obtain volumetric PET parameters can be time-consuming and (labor)-intensive, DmaxVox may be an easy-to-implement prognostic biomarker in clinical centers where automated segmentation software is not (yet) available,” pointed out Kleiburg and colleagues.
Three Key Takeaways
1. Baseline PSMA PET/CT may predicts prognosis. Baseline PSMA PET/CT scans provide valuable prognostic information for metastatic castration-resistant prostate cancer (mCRPC) patients, independently of PSA levels or treatment lines.
2. Key imaging parameters and survival. Doubling of PSMA tumor volume (PSMA-TV) and total lesion uptake (TL-PSMA) are associated with a 41 percent and 40 percent higher likelihood, respectively, of reduced overall survival (OS). DmaxVox (distance between furthest lesions) increases by 10 cm correlate with a 31 percent higher likelihood of lower OS.
3. Simplified prognostic tools. In the absence of automated segmentation software, DmaxVox may serve as an easy-to-implement alternative biomarker for assessing prognosis in mCRPC patients, particularly in resource-constrained settings.
In a lesion-level analysis involving 241 lesions, the study authors also found that doubling of the mean standardized uptake value (SUVmean) was associated with a 72 percent higher likelihood of lower OS. They also noted that bone lesions were associated with the highest rate of progression (40 percent) on PSMA PET/CT in comparison to 25 percent for lymph node lesions and 16 percent for visceral lesions.
“We hypothesise that this is caused by the relatively high density and low vascularisation of bone and by the bone marrow microenvironment, which may protect prostate cancer cells from treatment effects,” added Kleiburg and colleagues.
(Editor’s note: For related content, see “What SPECT/CT May Reveal About Early Treatment Response for Pluvicto in Patients with mCRPC,” “Study Shows Discordance Between PSMA PET/CT and PSA Response in 47 Percent of Patients Treated for mCRPC” and “Can Targeted PSMA PET/CT-Guided Radiotherapy Have an Impact for Oligometstatic Prostate Cancer?”)
In regard to study limitations, the authors conceded variability with injection to scan times as well as prior systemic therapies in the cohort. They also acknowledged a lack of validation data in the lesion-level analysis.
