Rising ALP Blood Levels During Peptide-Based Cancer Therapy May Signal Poor Treatment Response | Research

The takeaway

In neuroendocrine tumor patients receiving peptide receptor radionuclide therapy, rising alkaline phosphatase during treatment was linked to nearly halved progression-free survival (12.5 vs. 24.3 months).

24.3 vs 12.5 months PFS
Patients with decreasing ALP during PRRT had nearly double the progression-free survival compared to those with increasing ALP

What the researchers found

In 141 patients with metastatic neuroendocrine tumors undergoing peptide receptor radionuclide therapy (PRRT) with [177Lu]Lu-DOTATOC, rising alkaline phosphatase (ALP) levels during treatment were associated with significantly worse outcomes. Patients whose ALP decreased by more than 10% during PRRT had a median progression-free survival (PFS) of 24.3 months, compared to just 12.5 months for those whose ALP increased by more than 10%.

Progression, relapse, or death occurred in 103 of 141 patients (73%). Significant ALP differences between patients with low vs. high PFS were detectable before the third and fourth treatment cycles, suggesting ALP could serve as an early warning marker during PRRT.

Why it matters

PRRT is one of the most important peptide-based cancer therapies, but clinicians lack reliable ways to monitor whether treatment is working during the course of therapy. This study identifies ALP changes as a simple, inexpensive blood marker that could help doctors identify patients who are responding poorly — potentially allowing earlier treatment adjustments.

How the study worked

Retrospective analysis of 141 patients with metastatic neuroendocrine tumors treated with [177Lu]Lu-DOTATOC PRRT at a single center. Laboratory values measured before each PRRT cycle were compared to pretherapeutic baselines. Changes in plasma markers were analyzed using Wilcoxon rank-sum tests, and survival outcomes were assessed using Kaplan-Meier analysis.

Who was studied

141 patients with metastatic neuroendocrine tumors undergoing PRRT (median age not specified; 103/141 experienced progression, relapse, or death)

What this study cannot tell us

This is a retrospective, single-center study, limiting generalizability. The analysis is exploratory and requires prospective validation. ALP can be influenced by many factors beyond tumor progression (liver function, bone metabolism), which could confound interpretation. The abstract notes that findings should be interpreted cautiously.

How to read the evidence

This is a moderate-grade retrospective study with a meaningful sample size (141 patients) and clear statistical results. However, its single-center design and exploratory nature mean the findings need prospective validation before clinical adoption.

When this study was published

Published in 2023, this is recent research addressing an active clinical need in PRRT monitoring for neuroendocrine tumors.

The bigger picture

PRRT with lutetium-177-labeled somatostatin analogs is an established treatment for advanced neuroendocrine tumors, but response monitoring relies heavily on imaging. Finding simple blood-based biomarkers like ALP that track treatment response in real time could make PRRT management more proactive and potentially improve outcomes through earlier intervention.

Questions still open

Can ALP changes be validated prospectively as a reliable real-time biomarker for PRRT response in a larger, multicenter study?
Would combining ALP with other plasma markers (like chromogranin A or De Ritis ratio) improve predictive accuracy during PRRT?
Should patients showing rising ALP during PRRT be switched to alternative treatments earlier, and would this improve survival?

Common questions

What is peptide receptor radionuclide therapy (PRRT)?

PRRT is a targeted cancer treatment that uses radioactive atoms (like lutetium-177) attached to peptides that bind specifically to receptors on neuroendocrine tumor cells. The peptide delivers the radiation directly to the tumor, minimizing damage to surrounding healthy tissue. DOTATOC is one of the somatostatin analog peptides used in this therapy.

Why is alkaline phosphatase useful as a monitoring marker during PRRT?

ALP is a simple, inexpensive blood test that reflects activity in the liver, bones, and other tissues where neuroendocrine tumors commonly spread. A rising ALP during treatment may indicate that the cancer is progressing despite therapy, giving doctors an early warning signal — potentially before imaging studies would show tumor growth.

Read the original research

Plasma Markers for Therapy Response Monitoring in Patients with Neuroendocrine Tumors Undergoing Peptide Receptor Radionuclide Therapy.

Cancers, 15(24)

View on PubMed ↗Publisher’s paper ↗

Citation

Wetz, Christoph; Ruhwedel, Tristan; Schatka, Imke; Grabowski, Jane; Jann, Henning; Metzger, Giulia; Galler, Markus; Amthauer, Holger; Rogasch, Julian M M. (2023). Plasma Markers for Therapy Response Monitoring in Patients with Neuroendocrine Tumors Undergoing Peptide Receptor Radionuclide Therapy.. Cancers, 15(24). https://doi.org/10.3390/cancers15245717