Chemo day four did not arrive loudly.
It did not announce itself with alarms or sudden chaos.
It came quietly, settling into Cylus’s body the way a storm settles into the air before anyone realizes how violent it will become.
Immunotherapy day three followed closely behind, layering itself over everything he was already enduring, turning discomfort into pain and pain into something far harder to describe.
Cylus is hurting.
Not in one place.
Not in one clear way that can be easily treated.
But everywhere.
The kind of pain that moves through nerves, that lights up the body from the inside, that makes even rest feel like work.
The immunotherapy — dinutuximab — is doing what it is designed to do, and that knowledge is both reassuring and devastating at the same time.
Dinutuximab targets GD2 antigens, which sit on the surface of neuroblastoma cells.
It binds to them, flags them, and tells the immune system to attack.
But neuroblastoma is a cancer of immature nerve cells in the sympathetic nervous system, and that means the treatment cannot cleanly separate what is dangerous from what is healthy.
So while it damages cancer cells, it also damages healthy nerve cells.
That is where the pain comes from.
Deep, sharp, burning nerve pain that spreads across the entire body.
To manage that pain, doctors have placed Cylus on a PCA pump, carefully balancing medications to give him relief without overwhelming his small system.
Even with that support, the pain still breaks through.
High fevers come and go.
Immune reactions flare suddenly.
His body is constantly reacting, adjusting, fighting, and recalibrating.
It is exhausting for him in ways that go far beyond physical tiredness.
It drains him emotionally, too, even if he cannot fully articulate why.
Friday morning brought an X-ray of his pelvis.
Everyone knew its limitations.
An X-ray is not as detailed as a CT scan.
It does not offer the clarity of an MIBG scan.
But still, the results mattered.
And when they came back, they brought a moment of cautious relief.
For the first time in many months, doctors could not see any new tumors.
There was no obvious progression.
The area appeared stable.
In the world of pediatric cancer, “stable” is not a small word.
It does not mean cured.
It does not mean safe.
But it means the disease is not advancing — and sometimes, that pause is everything.
For Cylus’s mother, that news landed with mixed emotions.
Relief, yes.
But also heartbreak.
Because stability has come at such a high cost.
Nothing in her life has ever broken her heart the way watching her child endure this has.
Not once.
But over and over again.
Just one week ago, life looked different.
They were celebrating his birthday.
He was walking on his own.
Eating without struggle.
Smiling easily.
Playing like a child should.
Those moments may have looked ordinary to others, but to her they were sacred — proof that joy still existed between treatments, proof that her son was still fully himself.
And then, just as quickly, everything changed again.
Hospital rooms replaced birthday decorations.
IV lines replaced toys.
Pain replaced laughter.
Cylus does not understand why this keeps happening to him.
He does not understand words like immunotherapy, antibodies, or cancer cells.
He only knows that his body hurts in ways it did not before, and that the things he could do last week suddenly feel impossible.