PD-L1—A Doorway
A doorway, not a promise.
PD-L1 stands for programmed death-ligand 1.
It is a protein that can appear on some cancer cells and some immune cells. In normal biology, PD-L1 helps keep the immune system from attacking healthy tissue too aggressively.
But some cancers can use that same signal as a shield.
PD-L1 can bind to PD-1 on T cells — immune cells that help recognize and attack threats. When that connection happens, the immune response may slow down.
In plain language, the cancer may be sending a message that says:
“Don’t attack me.”
Immunotherapy drugs that target the PD-1/PD-L1 pathway are designed to interrupt that signal.They do not attack cancer in the same direct way chemotherapy does. Instead, they may help the immune system recognize and respond to cancer cells that were hiding behind that brake.
PD-L1 is not the whole map.
It is one signal — one clue — that can help guide the next treatment conversation.
Why PD-L1 Matters in PSCC
Penile squamous cell carcinoma, or PSCC, is rare.
Because it is rare, treatment decisions often depend on a careful combination of information: imaging, pathology, biopsy, molecular testing, clinical judgment, and the patient’s goals.
PD-L1 expression may help doctors ask an important question:
Is this cancer using an immune-escape pathway?
If the answer is yes, immunotherapy may become part of the conversation.
That does not mean PD-L1 is perfect.
A high PD-L1 result does not guarantee immunotherapy will work.
A low PD-L1 result does not always mean immunotherapy cannot help.
And PD-L1 does not replace biopsy, imaging, genomics, or the larger clinical picture.
It is one piece of the puzzle.
Why Testing May Need to Happen Again
A primary PSCC tumor and a lung lesion may not tell the exact same story.
Cancer can change over time. It can evolve under treatment pressure. It can behave differently in a metastatic site than it did in the original tumor. This what I have been learning this weekend. Again, do not take this as medical advice, it’s not. It’s my best effort to grok what is happening to me and be as ready as I can to work with my medical team.
That is why, when possible, doctors may want tissue from the new lesion — through biopsy or cytology — rather than relying only on the original tumor. My lung tissue was sent to Natera for this reason.
The question is not only:
What was the cancer before?
The question becomes:
What is the cancer doing now?
If a lung lesion is confirmed as recurrence, PD-L1 testing may help describe part of the biology of that recurrence. It may help guide the discussion around immunotherapy, chemotherapy, combination treatment, clinical trials, or other options.
How PD-L1 Is Measured
PD-L1 is usually measured on tumor tissue.
Reports may describe the result in different ways, including:
TPS — Tumor Proportion Score
This estimates the percentage of tumor cells showing PD-L1 expression.
CPS — Combined Positive Score
This includes PD-L1 expression on tumor cells and certain immune cells.
A report may describe PD-L1 as negative, low, intermediate, or high depending on the cancer type, test used, scoring system, and clinical context.
The exact meaning of a PD-L1 result should always be interpreted by the oncology team.
High, Intermediate, or Low Does Not Mean Simple
It is tempting to read PD-L1 like a traffic light.
High means go.
Low means stop.
Intermediate means maybe.
But cancer rarely speaks that cleanly.
A higher PD-L1 result may suggest that the tumor is using the PD-1/PD-L1 pathway to avoid immune attack. In some cancers, higher PD-L1 expression can be associated with a greater chance of response to checkpoint inhibitor therapy. I will ask this question at my next Oncology appointment.
But PD-L1 is an imperfect biomarker.
Some people with high PD-L1 do not respond.
Some people with low or negative PD-L1 still benefit.
That is why PD-L1 should not stand alone.
It belongs beside other pieces of information:
Imaging — What is growing? How fast? Where?
Biopsy or cytology — What is my lesion?
Genomic testing — What mutations or alterations are present? I believe this is where my Tempus Assay may shed light.
MSI-H / dMMR and TMB-H status — Are there broader signs that immunotherapy may be useful?
Clinical condition and goals — What treatment makes sense for me, not just the tumor? We have to assess past treatment’s side effects, including the ones that are cumulative like my neuropathy.
My Lung Recurrence Question
When PSCC moved to my lung, everything became more urgent — and also more precise (the additional wedge of nodes, the Tempus and Signatera assays…). I intuitively felt this as we quickly moved ahead with my lung tumor (seen over multiple times on scans). GRRRRR! My labs were finished in just a few hours after the needle stick.My thoracic surgery consult was schedule ASAP! I was offered lung surgery ASAP!
A lung nodule is not automatically one thing like I originally assumed.
It may be recurrence, we found out mine is/was. We hoped I would have an original lung cancer (aka a new primary cancer), but my tumor (and the adjacent node) were PSCC.
A lung nodule may be something else entirely.
Imaging (CT) can raise a concern, but a tissue sample often brings the clearest answer once pathology sees it. NOTE: My node in the wedge was not seen in the CT. CT scans “see” structure, like millions of cancer cells. While my node was hidden, it may have had a large number of cancer cells, just not enough for the CT to resolve.
If and when recurrence is confirmed, then PD-L1 testing becomes one part of understanding the current disease.
It asks:
Is this recurrence showing signs of immune escape? I need to learn more about this.
Could immunotherapy be part of the plan? And if so, what are the next questions? Which one(s)? How long? Chemo?
Do my lung lesion and the original PSCC match, or has the biology shifted? I need to wait to learn this.
Those questions matter because treatment is not just about attacking cancer. It is about choosing the right tools for the cancer that exists now. Also, I learned yesterday (from a breast cancer YouTube seminar) that some cancers can develop resistance, so that has to be part of the decision process.
The Big Idea
PD-L1 is not the whole map.
It is one marker. One signal. One clue.
But in a rare cancer like PSCC — especially when recurrence reaches the lung — clues matter.
My research so far suggests PD-L1 testing can help show whether the cancer may be interacting with the immune system in a way that could be targeted. If so it MAY help support a more personalized treatment discussion. And it can sit beside other tests, including imaging, biopsy, genomic profiling, MSI/MMR status, TMB, and clinical assessment.
Our goal is not just to collect data. That is just the phase we have been in since thoracic surgery.
The goal is to turn uncertainty into direction.
Detection leads to confirmation.
Confirmation leads to decision.
Decision leads to treatment.
And treatment, when carefully chosen, gives the next step a name.
- Ty