GIST Specialist for Marina del Rey, CA
A gastrointestinal stromal tumor on targeted therapy can look larger on a scan while it is actually responding well. Misreading that leads to drugs being abandoned that were working. Joshua Ellenhorn, MD, FACS interprets response the way this tumor requires.
- Response assessment using density as well as size
- Clinical Professor of Surgery, Cedars-Sinai Medical Center
- Surgical reassessment once a response has plateaued
- Twenty five to thirty minutes via Lincoln and Venice
Bigger Is Not Always Worse
Most cancer response is judged by diameter. The tumor shrinks, the treatment is working; the tumor grows, it is not. That rule is embedded in the standard criteria radiologists apply, and for most cancers it serves well enough.
GIST breaks it in both directions. A tumor responding to imatinib frequently changes consistency before it changes size, turning from dense solid tissue into something softer and more fluid-like. On a scan that shows as a marked fall in density with the diameter barely moving, which size criteria record as stable disease and a patient hears as the drug is not working. Occasionally a responding tumor bleeds internally and genuinely enlarges for a period, which reads as progression and is nothing of the kind.
The reverse trap is equally common. Liver deposits that started out the same density as the surrounding liver are effectively invisible on the first scan. As they respond and lose density they become visible, and a report describes new lesions. They are not new. They were always there and are now declaring themselves precisely because the treatment is working.
All of this is well described and the criteria to handle it exist. What it requires is someone reading the scan who knows this is GIST and not applying diameter alone.
What Each Imaging Pattern Usually Means
These are the patterns that get misread most often. If your report describes one of them, the second column is the question to raise.
| What the scan shows | What it often actually means | What should happen |
|---|---|---|
| Size unchanged, density markedly reduced | A genuine response. Solid tumor has become softer and less dense without shrinking much | Continue the drug. This is success, not stability |
| Tumor larger, density lower | Frequently bleeding or fluid change within a responding tumor | Do not abandon the drug on size alone. Reassess with density and, if unclear, PET |
| New low density liver lesions | Deposits that were previously the same density as liver becoming visible as they respond | Compare against the original scan. Often old disease declaring itself, not new spread |
| A solid nodule inside a low density mass | A resistant clone growing within an otherwise controlled tumor | Genuine focal progression. Consider resecting or ablating that site to extend the drug |
| Everything growing together | Generalised progression | Change of drug rather than an operation. Sunitinib, then regorafenib, then ripretinib |
| Stable for a year or more, limited residual disease | Sustained control with a well defined remaining target | Worth a surgical reassessment, which frequently never happens |
PET/CT resolves most of these quickly because metabolic activity falls within days to weeks of an effective drug, well before any structural change.
The Biology Behind the Imaging
GIST arises from the interstitial cells of Cajal, pacemaker cells inside the wall of the digestive tract that coordinate the contractions moving food along. Nearly all carry a mutation in KIT or PDGFRA locking a growth signal permanently on, and targeted tablets were built to switch precisely that off.
When they do, the tumor does not simply disappear. Cells die, the tissue becomes less cellular and less vascular, and what was dense solid tumor becomes softer material with a lower density on CT. The volume it occupies can take months to reduce, and sometimes barely does. The mass is still there while the disease inside it is being controlled.
That is why density carries more information than diameter here, and why a criteria set built for shrinking carcinomas mismeasures this tumor. It is also why a scan should always be compared against the previous one rather than read in isolation, and why keeping your prior imaging accessible is worth the administrative effort.
When Surgery Follows a Response
Recordings of real GIST resections narrated by the surgeon who performed them. Reading the response correctly is what determines the right moment for these.
Laparoscopic Resection of a Gastric GIST
A gastric GIST removed through small incisions with the capsule kept intact.
Gastric GIST Resection: A Simplified Approach
A refined approach that shortens operating time and recovery.
Robotic Resection of a Duodenal GIST
Duodenal GIST removed robotically with the pancreas and bile duct preserved.
Timing Is the Whole Question
Operating too early, into an active and widespread response, achieves less than the drug would. Never reassessing at all leaves patients on medication indefinitely when resecting a small residue might have consolidated the gain. Both are common.
Certifications and Appointments
Two American Board of Surgery certifications, a Cedars-Sinai teaching appointment, and membership of the societies that publish the response criteria referenced above.
- American Board of Surgery, certified in General Surgery
- American Board of Surgery, certified in Colorectal Surgery
- California State Medical License
- Florida State Medical License
Joshua Ellenhorn, MD, FACS
Dr. Ellenhorn is a surgical oncologist and Clinical Professor of Surgery at Cedars-Sinai Medical Center, and a collaborative member of the Samuel Oschin Comprehensive Cancer Institute.
Response interpretation is an unusual thing for a surgeon to care about, and it is exactly why it belongs here. The decision to operate on treated GIST depends entirely on reading the imaging correctly: whether progression is focal or general, whether apparent growth is real, whether a plateau has been reached. A surgeon who leaves that to the report and operates on request will operate at the wrong times. Following the response data closely is part of knowing when not to operate.
He is certified by the American Board of Surgery in General Surgery and in Colorectal Surgery, a Fellow of the American College of Surgeons, and a member of the Society of Surgical Oncology and the American Society of Clinical Oncology. He practises with the Surgery Group of Los Angeles.
Questions About Your Scan Report
Bring these to whoever is managing your medication. They are answerable from imaging you have already had.
- Was density assessed, or only size?
- Have the Choi criteria been applied to my scans?
- Was this scan compared directly against my previous one?
- Are any apparently new lesions genuinely new?
- Is there a solid nodule within a treated mass?
- Is any progression focal or generalised?
- Has a PET been considered to clarify response?
- Has my case been reassessed for surgery since the response plateaued?
What Patients Say
Reviews left by patients treated by Dr. Ellenhorn at the Surgery Group of Los Angeles.
★★★★★I was very pleased with the office staff, they were always very pleasant and helpful. I was very impressed with Dr. Ellenhorn as well. He was very friendly and addressed all my concerns regarding my surgery and aftercare and follow up.
Terry Jackson
★★★★★Very kind stuff, great service. Dr Joshua Ellenhorn is a very calm doctor who takes time with his patient.
Anita Lukacevic
From Marina del Rey
Lincoln Boulevard north to Venice or Washington and then east is the usual route and tends to hold steadier at peak than the freeway. The 90 east to the 405 north to the 10 is quicker off peak. From the Peninsula and Via Marina side, allow a few extra minutes to get out to Lincoln. Twenty five to thirty minutes overall.
The office is in the medical plaza attached to Cedars-Sinai Medical Center, where imaging and the reporting radiologists are in the same building as the surgical consultation. For the questions on this page that adjacency is the substance rather than a convenience: scans can be reviewed alongside the prior studies and discussed directly rather than through a report.
Patients travelling from outside the region, including Arizona and Nevada, can have imaging reviewed remotely.
8635 W 3rd St, Suite 880W
Los Angeles, CA 90048
Monday to Saturday, 11:00am to 8:00pm
Closed Sunday
Frequently Asked Questions
My tumor got bigger on imatinib. Does that mean it is not working?
What are the Choi criteria?
New spots appeared in my liver. Is the disease progressing?
What does nodule within a mass mean?
Is PET scanning useful?
Should I be worried if my scan report says stable disease?
Why does it matter who reads the scan?
How far is your office from Marina del Rey?
Do Not Abandon a Working Drug on Size Alone.
A responding gastrointestinal stromal tumor can look unchanged or even larger while the treatment is working. Have the imaging read against the prior studies before any decision to switch or operate.
