Chapter 52: Antineoplastic Drugs Part 1 – Cancer & Cell-Specific Agents

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Welcome to the Deep Dive.

Today, we're tackling, well, a really complex topic, but it's absolutely essential for anyone in healthcare.

We're talking about the foundational pharmacology of anti -neoplastic drugs.

Specifically, zero in on the cell cycle specific agents,

drawing everything straight from Chapter 52 of Lilly's Pharmacology for Canadian Healthcare Practice.

Yeah.

And our mission today for you listening is really to take this chapter, which can look like just a huge list of drugs and confusing terms and turn it into something you can actually use.

We want you to get why the drugs work the way they do, how they target cancer, and critically what that means for nursing care, the why behind the side effects and the interventions.

Okay.

So let's set the scene first.

Before the drugs, the disease itself, cancer, basically is when cells just lose control.

They start growing without stopping, often because of some genetic change, and they can invade other tissues,

spread, metastasize.

Exactly.

And it's crucial to understand the difference between, say, a benign tumor and a malignant one.

A benign tumor, well, it's usually contained.

It might be in a capsule.

It grows slowly.

And importantly, it doesn't metastasize, doesn't spread.

It can still cause problems, you know, by pressing on things, but it stays put.

But the real fight, the focus for these kinds of drugs is the malignant tumor.

That's the one.

Malignant tumors are invasive.

They push into surrounding tissues.

The cells often look weird, undifferentiated.

That's called anaplasia.

And the big danger is metastasis.

They can break off and set up shop somewhere else in the body.

Unpredictable.

And we categorize these based on where they originate.

We do.

You've got carcinomas, which start in epithelial tissues like skin or the lining of your gut.

Then sarcomas, those arise from connective tissues, think bone, muscle, fat.

And then there are lymphomas, which are actually solid tumors in the lymphatic system.

And finally, leukemias.

Those aren't solid tumors.

They're cancers of the blood -forming cells in the bone marrow circulating around.

So if cancer is fundamentally about uncontrolled cell growth, then the strategy makes sense.

Attack the process of growth itself, which means we need to understand the cell cycle.

Can you walk us through that quickly?

Sure.

Think of a cell's life.

Most of the time, normal cells are just kind of hanging out in the G0 phase, resting, not dividing.

But when they get the signal to divide, they enter G1.

That's gap one.

They start making enzymes and proteins needed for the next step.

The really key phase for many drugs is the S phase synthesis.

This is where the cell duplicates all its DNA.

Critical step.

Then comes G2, another prep phase, making more proteins and RNA.

And finally, M phase mitosis.

That's the actual physical splitting of the cell into two daughter cells.

Right.

And that cycle, G1, S, G2, M, is the target.

The drugs we're focusing on today are cell -cycle specific, or CCS.

Correct.

CCS drugs only kill cells that are actively in a specific part of that cycle.

Maybe they only work during S phase or only during M phase.

This is different from the other main categories, cell -cycle nonspecific, or CCS drugs.

Those guys can damage a cell pretty much any time, whether it's actively dividing or just resting in G0.

Okay.

So if CCS drugs need the cell to be in a specific phase,

what does that tell us about the kinds of cancers they're most effective against?

That's a really important clinical point.

They work best on tumors that are dividing rapidly.

Cancers with a high growth fraction, meaning a large percentage of cells, are actively cycling, not resting in G0.

Think about things like leukemias and fomas.

Cancers where the cells are just constantly churning through that cycle.

A slow growing tumor with lots of cells in G0.

A CCS drug might not be nearly as effective.

But here's the downside, the really tough part of traditional chemo.

These drugs, they're powerful, but they're not smart, are they?

They hit any rapidly dividing cell.

That's the fundamental problem.

They can't tell the difference between a rapidly dividing cancer cell and a rapidly dividing normal cell.

And that lack of specificity is where almost all the major side effects come from.

Our bodies rely on cells dividing quickly in certain areas, like - Neurophils.

Right.

Hit those and you get alopecia, hair loss, very common, very distressing.

And the lining of our entire GI tract.

Exactly.

That lining replaces itself constantly.

So chemo hits it hard.

That leads to stomatitis, those painful sores in the mouth, nausea, vomiting.

The emetic potential is a huge factor nurses plan for.

And diarrhea.

The whole gut can be affected.

And the third, often the most critical area,

the bone marrow.

Yes, myelo suppression.

This is often the most dangerous toxicity.

The bone marrow is the factory for all our blood cells.

So when chemo suppresses it, you get three major problems.

One, leukopenia, especially a drop in neutrophils called neutropenia, that wipes out the immune system's front line, massive infection risk.

Two, anemia, not enough red blood cells that causes fatigue, weakness, shortness of breath.

And three, thrombocytopenia, low platelets.

That means a high risk of bleeding.

And sometimes these side effects, especially the bone marrow suppression or severe GI toxicity, become the thing that stops us from giving a higher, maybe more effective dose of the drug.

That's the dose limiting adverse effect, right?

Precisely.

You hit a wall where the damage to normal tissues is just too great to safely increase the dose.

And nurses absolutely have to know about the nadir.

That's the point in time after a chemo dose when the blood cell counts reach their absolute lowest, usually somewhere between 10 and 28 days.

That nadir window is peak vulnerability for infection and bleeding.

You have to anticipate it.

Okay, got it.

Let's dive into the specific CCS drug classes now.

First up, the anti -metabolites.

They target the S -phase.

Right, S -phase DNA synthesis.

These drugs are clever, in a way.

They're analogs, meaning they look chemically similar to the natural building blocks cells need to make DNA and RNA, things like folic acid or the purines and pyrimidines.

So the cell basically gets tricked into taking up the drug instead of the real thing.

Then the drug either gums up a key enzyme needed for synthesis, or it actually gets incorporated into the new DNA strand, making it faulty and useless, sabotage from within.

A classic example is methotrexate.

That's a folate antagonist.

Yeah, it blocks the enzyme dihydrofolate reductase, which is needed to activate folic acid.

No act of folic acid, no DNA synthesis.

Simple, but effective.

But this leads to something incredibly important clinically.

Leucovorin rescue.

High -dose methotrexate is so potent, it would kill too many normal cells.

So you give leucovorin, which is a pre -activated form of folic acid, on a very specific schedule after the methotrexate.

The timing is critical.

It rescues the normal cells, while hopefully allowing the methotrexate enough time to kill the cancer cells.

It's a balancing act.

Wow, okay.

And there are others in this class, like sluracil, or 5 -FU, and its oral form, cabecetabine.

Yes, those are pyrimidine antagonists.

Same principle, they interfere with the building blocks of DNA.

Oh, and with anti -metabolites, especially when they work really well and kill lots of cells quickly, you have to watch out for tumor lysis syndrome.

All the stuff inside the dead cancer cells gets released into the bloodlots of potassium, phosphate, uric acid.

It can cause kidney failure, heart problems.

It's an emergency.

Often managed with drugs like allopurinol to handle the uric acid.

Good point.

Okay, next class, mitotic inhibitors.

These target the M and G2 phases, cell division itself, and many come from plants.

That's right.

You have the vinca alkaloids, like finchristine from the periwinkle plant, and the taxans, like pachlitaxel, originally from the pacific yew tree.

Their job is to mess up the cell's internal skeleton, the microtubules.

These form the mitotic spindle, which is supposed to pull the copied chromosomes apart during M phase.

These drugs interfere with that process, either preventing the spindles from forming or from breaking down correctly.

Either way, the cell gets stuck mid -division and dies.

Let's talk about vincristine.

It's known for being less harsh on the bone marrow sometimes, but it has a major toxicity elsewhere.

Neurotoxicity, yes.

Peripheral neuropathy is very common.

Numbness, tingling, pain in hands and feet.

But the critical, never ever miss this point about vincristine is the administration route.

It is absolutely fatal if given interlithically, meaning into the spinal fluid.

It causes devastating, irreversible neurological damage and death.

This is such a known risk that there are global safety standards, like always diluting it in a small IV bag, never putting it in a syringe that could possibly be mistaken for an intrathecical medication.

It's a zero tolerance error.

That is incredibly important, a stark reminder.

What about paclitaxel?

Any specific precautions there?

Paclitaxel has issues with its formulation.

It doesn't dissolve well in water, so it needs special solvents.

These solvents, unfortunately, can cause severe hypersensitivity reactions like an allergic reaction during the infusion.

So standard practice is mandatory pre -medication, usually a steroid like dexamethasone plus antihistamines, both H1 and H2 blockers, given before the paclitaxel infusion starts, to try and prevent or lessen that reaction.

Got it.

Moving on to the topoisomerase inhibitors.

Drugs like topotechin and ironotechin, they hit the S and G2 phases.

Right.

These target an enzyme called topoisomerase I.

Think of DNA like a tangled phone cord during replication.

Topoisomerase I normally makes temporary cuts in the DNA strands to relieve the tension, let them unwind, and then it reseals the cuts.

These drugs, the camtothessins, essentially trap the enzyme after it makes the cut but before it can reseal it.

So you get permanent DNA strand breaks and the cell can't survive that.

Okay, and ironotechin has a particularly notorious side effect.

Diarrhea.

Severe diarrhea.

It's kind of a two -punch problem.

First, there's an acute cholinergic diarrhea that can happen almost immediately, during or right after the infusion.

It's related to acetylcholine release, causes cramping, sweating.

It's treated with atropine.

But then, often days later, maybe two to ten days post -infusion, you can get delayed diarrhea.

And this one can be incredibly severe, profuse, leading to dehydration, electrolyte chaos.

It can be life -threatening.

It needs really aggressive management, usually with high -dose lopramide, way beyond the usual over -the -counter doses following specific protocols.

Oh, okay.

That's definitely one to watch closely.

Lastly, a more specialized group, the antineoplastic enzymes.

Hesperogenase, pigaspargase.

Targeting G1 phase.

Yeah, these are interesting because their mechanism is quite unique, mainly used for acute lymphocytic leukemia, ALL.

They are enzymes that break down the amino acid asparagine in the bloodstream.

Most normal cells can make their own asparaging, but certain leukemia cells can't.

They rely on getting it from the blood.

So, by destroying the external supply of asparagine with these enzymes, you effectively starve the leukemia cells.

And their main toxicity isn't the usual myelosuppression.

Not primarily, no.

The big concern with asparagenase in its longer -acting form, pigaspargase, is pancreatic toxicity.

It can cause severe, sometimes fatal pancreatitis.

It can also mess with blood sugar, leading to hyperglycemia.

So, monitoring pancreatic enzymes and glucose levels is absolutely critical with these drugs.

Okay, we've covered a lot of mechanisms and specific risks.

Let's pull this together now with nursing considerations.

What are the absolute priorities for assessment?

Well, you're constantly assessing the systems you know are vulnerable because of rapid cell division.

So, meticulous GI assessment.

Asking about nausea, timing, samarity, tracking bowel movements, frequency, consistency, watching for that urinotech and diarrhea.

You need to be inspecting the mouth daily for signs of stomatitis, redness, sores, pain.

And checking the skin, especially palms and soles, for redness or blistering, which can happen with some drugs that's palmar plantar dysesthesia.

In terms of lab work, it's all about the blood counts.

Absolutely.

Frequent monitoring of the CBC is non -negotiable.

You are watching for and anticipating that negir.

Seeing the white count or platelet count start to drop is your cue to implement precautions, infection control for neutropenia, bleeding precautions for thrombocytopenia before the patient becomes critically ill.

We also have to touch on fertility.

These drugs attack dividing cells.

That includes sperm and egg cells.

Yes.

This is a really important conversation to have with patients of reproductive age before treatment starts.

There is a significant risk of temporary or permanent sterility.

And because these drugs can cause birth defects, their teratogenic reliable contraception is essential during treatment and often for months, sometimes up to two years afterwards for both men and women.

Thinking about implementation, putting this into action, preventing nausea and vomiting.

Pre -medicate.

Give those anti -medics 30 to 60 minutes before the chemotherapy infusion starts.

Don't wait for the nausea to hit.

And for stomatitis care.

Patient education is key.

They need to avoid irritants.

Alcohol -based mouthwashes are out.

Very hot, very spicy foods.

Acidic things like citrus avoid them.

Gentle oral hygiene is crucial.

Soft toothbrush or maybe even tooth vets if it's really sore, keeping the mouth moist.

And let's revisit that immediate IV risk.

Extravagation.

A vesicant drug leaking out.

This is an emergency during infusion.

If you suspect extravagation, pain, swelling, redness at the IV site, loss of blood return, the absolute first step is estopedia infusion immediately.

Critically leave the IV catheter in place initially.

Don't pull it out.

You might need to use that access to try and administer an antidote directly into the area.

For vinca alkaloids or at the side, the antidote is often hyaluronidase.

Then you follow your facility's specific extravagation protocol very carefully, which might involve aspirating residual drug, applying cold or warm compresses depending on the drug and elevating the limb.

Quick action minimizes tissue damage.

Right.

So which critical information here?

Okay, let's try to summarize the absolute must -know points for the listener.

Understand the cell cycle phases.

Know that CCS drugs target specific phases.

Except that side effects hitting hair, GI tract, and bone marrow are almost unavoidable with these traditional agents.

And those huge safety alerts.

Vincristine never intrathecally.

Irinotec can be ready for both early and severe delayed diarrhea.

Methotrexate needs leukovirin rescue.

And always, always anticipate the nadir.

Exactly.

And maybe one final thought to leave you with connecting this to the future.

Think about how much of the nursing care we just discussed.

Managing nausea, stomatitis, myelo suppression, extravagation.

It's all focused on dealing with the damage these drugs do to healthy, rapidly dividing cells.

Now consider the rise of targeted therapies.

Drugs designed to hit specific molecules only on cancer cells, ideally sparing normal cells.

As those therapies become more common, how might that fundamentally change what oncology nursing looks like day to day?

What will the focus of our care become?

That's a really interesting question to ponder.

Something to think about as the field evolves.

Thank you so much for joining us for this deep dive today.

From the Last Minute Lecture Team, we appreciate you tuning in.