Lymphoma and Monoclonal Antibodies: Aiming at a Marker on the Cell
Old chemotherapy shrank lymphomas but rarely finished the job. Then someone added a single antibody — rituximab — to a decades-old regimen, and cure rates jumped. That antibody didn't poison the cell; it aimed at one marker on its surface and marked it for death. Follow that idea to its dramatic conclusion — re-programming a patient's own T cells to hunt the cancer — and you understand where blood-cancer therapy is heading.
For thirty years, CHOP was the standard chemotherapy for aggressive B-cell lymphoma — four drugs, real toxicity, and a cure for only some. Then a large trial added one more agent to the same four: an antibody called rituximab. No new poison, no harsher schedule — just a protein that finds a single marker (CD20) on the B-cell surface. The regimen was renamed R-CHOP, and survival curves separated in favour of the patients who got the antibody. That is the whole plot of this chapter: cancer of the lymphocytes, the chemotherapy that softens it, and the targeted antibodies — ending with T cells rebuilt to do the hunting themselves.
What lymphoma is: cancer of the lymphocyte
Lymphomas are malignancies of lymphocytes. They usually arise in lymph nodes rather than the marrow, and split into two great families. Hodgkin lymphoma (Hodgkin lymphoma) is defined by its distinctive Reed–Sternberg cell, spreads in an orderly node-to-node fashion, and is one of the most curable adult cancers. Non-Hodgkin lymphoma (NHL) is a much larger, more varied group — most of them B-cell in origin — ranging from indolent (slow) follicular lymphoma to aggressive diffuse large B-cell lymphoma (DLBCL). The same biology overlaps with chronic lymphocytic leukaemia (CLL), a B-cell malignancy that lives mostly in the blood and marrow; many of the drugs here treat both.
The chemotherapy backbones: ABVD and CHOP
Lymphoma is not treated with a single drug but with combination regimens — several agents with different mechanisms and non-overlapping toxicities, given together to hit the cancer from multiple angles and blunt resistance. Two backbones dominate. For Hodgkin lymphoma: ABVD (Adriamycin/doxorubicin, Bleomycin, Vinblastine, Dacarbazine). For B-cell NHL: CHOP (Cyclophosphamide, Hydroxydaunorubicin/doxorubicin, Oncovin/vincristine, Prednisolone). These are the classic cytotoxic (cell-killing) chemotherapy classes covered in the blood-cancer drugs overview chapter — alkylators, anthracyclines, vinca alkaloids, a steroid.
Notice the design principle: each drug in a regimen has a DIFFERENT dose-limiting toxicity. Doxorubicin threatens the heart, vincristine the nerves, bleomycin the lungs. Because the toxicities don't stack on one organ, you can give near-full doses of each — that is why combinations out-cure single agents. It also tells you which side effect to watch for from which letter.
Monoclonal antibodies: aiming at a surface marker
A monoclonal antibody (Monoclonal antibody) is a targeted immunotherapy, not chemotherapy. Instead of poisoning every dividing cell, it is a manufactured protein engineered to bind ONE specific surface marker (antigen) found on the malignant cell. Binding kills in three main ways: it flags the cell for immune destruction by natural killer cells (antibody-dependent cellular cytotoxicity, ADCC); it activates complement to punch holes in the membrane (complement-dependent cytotoxicity); or the antibody carries a toxic payload directly into the cell (an antibody–drug conjugate). You can spot these drugs by their generic name: the suffix "-mab" means monoclonal antibody. The same biologic technology powers the anti-TNF and other antibodies you meet in the Inflammation section — one platform, many targets.
Rituximab binds CD20, a marker present on B lymphocytes (and therefore on most B-cell lymphomas and CLL). Added to CHOP, it created R-CHOP and materially improved cure and survival in B-cell NHL; it is now a backbone of B-cell malignancy therapy. Key risks: infusion reactions (fever, chills, rigors during the first infusion, from cytokine release); increased infection risk from depleting normal B cells; and — the classic exam and safety point — reactivation of hepatitis B. Screen for hepatitis B BEFORE giving rituximab; latent virus can flare dangerously when B cells and immunity are suppressed.
Rituximab was the first, not the last. Obinutuzumab is a newer, engineered anti-CD20 antibody used in CLL and follicular lymphoma. Brentuximab vedotin targets a different marker, CD30, and is an antibody–drug conjugate — the antibody homes to CD30-positive Hodgkin (and some T-cell) lymphoma cells and delivers a microtubule poison inside them. And in Hodgkin lymphoma, checkpoint inhibitors (antibodies that release the brakes on the patient's T cells, such as the anti-PD-1 agents nivolumab and pembrolizumab) are highly active, especially in relapsed disease.
- Lymphoma = cancer of lymphocytes: Hodgkin (Reed–Sternberg, very curable) vs NHL (mostly B-cell).
- Treated with combination chemo backbones: ABVD (Hodgkin), CHOP (B-cell NHL).
- "-mab" = a monoclonal antibody: targeted immunotherapy against a surface marker, NOT chemo.
- Rituximab (anti-CD20) added to CHOP → R-CHOP; a landmark gain in B-cell NHL and CLL.
- Screen for hepatitis B before rituximab; also watch infusion reactions and infection.
- Brentuximab vedotin (anti-CD30 ADC) and checkpoint inhibitors are active in Hodgkin.
Targeted small molecules: BTK and BCL-2
Antibodies work from outside the cell; small-molecule inhibitors work inside it, blocking a signal the malignant cell depends on. Two matter most in CLL and some B-cell lymphomas. BTK inhibitors such as ibrutinib block Bruton tyrosine kinase, a switch in the B-cell receptor pathway that keeps the cancer alive; an oral pill, it transformed CLL therapy (watch for bleeding and atrial fibrillation). BCL-2 inhibitors such as venetoclax block the protein that lets the cancer cell evade apoptosis (programmed death) — restore the death signal and the cells die. Venetoclax is so effective that the cells can die en masse, releasing their contents and causing tumour lysis syndrome; it is started at a low dose and escalated slowly to prevent this.
The leap: CAR-T cell therapy
Follow the targeting idea to its extreme. Instead of a manufactured antibody, why not turn the patient's own immune cells into the weapon? In CAR-T cell therapy (chimeric antigen receptor T-cell therapy), a patient's T cells are collected, genetically engineered in the lab to display a receptor that recognises a lymphoma marker — usually CD19, another B-cell antigen — then multiplied and infused back. These living drugs seek out and destroy the malignant B cells. In refractory or relapsed B-cell lymphoma and leukaemia that had exhausted other options, CAR-T has produced dramatic, sometimes durable remissions.
When engineered T cells activate en masse against the tumour, they flood the body with inflammatory signals — cytokine release syndrome (CRS): high fever, falling blood pressure, and hypoxia that can escalate to shock. The specific antidote is tocilizumab, a monoclonal antibody that blocks the interleukin-6 (IL-6) receptor — the same anti-IL-6 biologic used in the Inflammation section for rheumatoid arthritis, borrowed here to switch off the cytokine storm. CAR-T also causes a distinct neurotoxicity (confusion, seizures). Both are why CAR-T is delivered only in specialised centres.
- BTK inhibitors (ibrutinib) and BCL-2 inhibitors (venetoclax) are oral targeted drugs in CLL.
- Venetoclax can trigger tumour lysis syndrome — start low, escalate slowly.
- CAR-T re-programs the patient's own T cells to target CD19; dramatic in refractory disease.
- CAR-T's signature toxicity is cytokine release syndrome (CRS), treated with tocilizumab (anti-IL-6).
- CAR-T also causes neurotoxicity; both toxicities demand specialised-centre care.
- Giving rituximab without screening for hepatitis B first — B-cell depletion can reactivate latent virus, sometimes fatally.
- Assuming any "-mab" drug is chemotherapy. Antibodies are targeted immunotherapy against a marker, with a different mechanism and side-effect profile.
- Forgetting cytokine release syndrome after CAR-T (or bispecific antibodies) — high fever and hypotension are CRS until proven otherwise, not just infection.
- Starting venetoclax at full dose — the rapid kill can precipitate tumour lysis syndrome.
Before starting rituximab for B-cell lymphoma, which screening test is essential to prevent a dangerous reactivation?
- Lymphomas are lymphocyte cancers — Hodgkin (very curable) and NHL (mostly B-cell) — treated with combination chemo (ABVD, CHOP).
- Monoclonal antibodies ("-mab") aim at a surface marker and kill via ADCC, complement, or a delivered payload — targeted immunotherapy, not chemo.
- Rituximab (anti-CD20) added to CHOP (R-CHOP) transformed B-cell NHL/CLL; screen for hepatitis B first.
- BTK (ibrutinib) and BCL-2 (venetoclax, watch tumour lysis) inhibitors add oral targeted options in CLL.
- CAR-T re-programs the patient's T cells against CD19 — dramatic in refractory disease; watch for cytokine release syndrome (treat with tocilizumab) and neurotoxicity.
- Katzung BG. Basic & Clinical Pharmacology — Cancer chemotherapy: monoclonal antibodies, targeted agents & immunotherapy.
- Hoffbrand AV, Moss PAH. Hoffbrand's Essential Haematology — Hodgkin & non-Hodgkin lymphoma; CLL; monoclonal antibody & CAR-T therapy.
- Brunton LL, et al. Goodman & Gilman's The Pharmacological Basis of Therapeutics — Targeted therapies & antibody-based agents in lymphoid malignancy.
- Longo DL, et al. Harrison's Principles of Internal Medicine — Malignancies of lymphoid cells; rituximab, brentuximab, checkpoint inhibitors & CAR-T.
- Whalen K. Lippincott Illustrated Reviews: Pharmacology — Anticancer monoclonal antibodies & signal-transduction inhibitors.
