STAR-CAP Suggested to be a Viable AJCC-Compliant Staging System for Prostate Cancer

November 26, 2020
Hannah Slater

According to the researchers, the high-quality evidence observed thus far supports the endorsement of this scoring system as a new staging system for prostate cancer.

A multinational cohort study published in JAMA Oncology suggested that experts have developed and validated a proposed American Joint Committee on Cancer (AJCC)-compliant clinical prognostic group staging system which can be used globally for patients with nonmetastatic prostate cancer and has better performance than the current AJCC 8th edition.1

The new proposed system — called STAR-CAP — utilizes patient, tumor, and outcomes data from nearly 20,000 patients from 55 centers in the US, Canada, and Europe to create a robust model with strong prognostic power. According to the researchers, the high-quality evidence observed thus far supports the endorsement of this scoring system as a new staging system for prostate cancer.

“Localized prostate cancer is sometimes less aggressive, sometimes more — and whether we’re patients, physicians or researchers, we all want to know as best we can how aggressive a particular cancer is likely to be,” co-first author Robert Dess, MD, an assistant professor of radiation oncology at Michigan Medicine, said in a press release.2 “That information helps with our conversations with patients, it helps with clinical trial design and it is particularly valuable when you can make those estimates based off of standard information that you would collect when you first see a patient to discuss their treatment options.”

This study included 7 centers within the US, Canada, and Europe, 5 centers within the Shared Equal Access Regional Cancer Hospital (SEARCH) Veterans Affairs Medical Centers collaborative, and 43 centers within the Cancer of the Prostate Strategic Urologic Research Endeavor (CaPSURE) registry. Patients included were those with cT1-4N0-1M0 prostate adenocarcinoma treated from January 1, 1992, to December 31, 2013.

The study cohort, dubbed the STAR-CAP cohort, was randomly divided into training and validation data sets. Importantly, statisticians were blinded to the validation data until the model was locked. A Surveillance, Epidemiology, and End Results (SEER) cohort was used as a second validation set.

Among a total of 19,684 patients included in the analysis (median age, 64.0 [IQR, 59.0-70.0] years), 12,421 were treated with radical prostatectomy and 7263 with radiotherapy. Median follow-up was 71.8 (IQR, 34.3-124.3) months; however, 4078 (20.7%) were followed up for at least 10 years.

The system assigns patients to a particular stage through a point system based on several variables, include age, tumor category, Gleason grade of cell abnormality, and prostate-specific antigen (PSA) levels. The model divides patients into 9 stages of non-metastatic prostate cancer based on their point score — from stage 1 to stage 3, with each stage split into substages of A, B and C.

In the validation set, predicted 10-year prostate cancer-specific mortality (PCSM) for the 9 score groups ranged from 0.3% to 40.0%. Notably, the 10-year C index (0.796; 95% CI, 0.760-0.828) exceeded that of the AJCC 8th edition (0.757; 95% CI, 0.719-0.792), revealing improvements across age, race, and treatment modality and within the SEER validation cohort. In addition, for a significant number of patients, the new model would reclassify them as having less advanced disease — for example, 22% of patients who would be classified as stage 3A under the AJCC’s 8th edition criteria would be classified as stage 1C using the STAR-CAP system, a downgrade of 4 classification steps.

“This is the kind of information that can give patients and doctors more confidence when discussing treatment options and expected outcomes,” said Dess.

Several years ago, the AJCC established criteria to evaluate prediction models for the staging of prostate cancer — however, since no models met the criteria, the most recent staging designations were based on the consensus of experts in the field.

“None of the previous models evaluated met the criteria, so none of them could be used,” co-senior author Daniel Spratt, MD, the Laurie Snow Endowed Research Professor of Radiation Oncology at Michigan Medicine, said in the release. “So, we said, ‘Well, let’s make one.’ We wanted it to be transparent, robust and validated, so that we can start moving closer to communicate using a common staging system, similar to other cancers. Right now, we primarily categorize people as low risk, intermediate risk or high risk — which is a fairly blunt and imprecise system.”

The scoring system is designed to be able to be used worldwide with information that is commonly gathered about a patient and their cancer. Importantly, this new system has been made available to doctors and researcher worldwide via a web-based app at STAR-CAP.org.

“We know that some of the newest tools that we have that are just coming online like genomics or molecular imaging may improve upon this system, but we wanted to create the best, most widely accessible model based on the data we currently have — understanding that new tools may help us develop even better models in the future,” Dess explained.

References:

1. Dess RT, Suresh K, Zelefsky MJ, et al. Development and Validation of a Clinical Prognostic Stage Group System. JAMA Oncology. doi: 10.1001/jamaoncol.2020.4922

2. Toward a New Staging System for Prostate Cancer, and Why it Matters [news release]. Published October 22, 2020. Accessed November 19, 2020. https://www.newswise.com/articles/toward-a-new-staging-system-for-prostate-cancer-and-why-it-matters?sc=sphr&xy=10021790

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