Understanding the Overall Picture of Cancer Treatment and Why Some Cancers Are “Easier” or “Harder” to Cure
“Can cancer really be cured?” “If it comes back, does that mean it is over?” These are among the most common and most painful questions for patients and their families.
In reality, though, “cancer” is not a single disease. How treatable it is depends heavily on:
- which organ it started in (cancer type)
- at what stage it was detected
- what “personality” the tumor has at the biological and molecular level
In this first article, we will build a mental “map” of cancer treatment and explain, in plain language, why some cancers are relatively curable while others remain very difficult to treat.
What you will learn in this article
- What “cancer” actually is from a biological point of view
- What stage, grade, and molecular subtype mean
- How the overall survival of cancer patients has improved in recent decades
- The three pillars of cancer treatment (surgery, radiotherapy, systemic therapy) and where newer treatments fit in
- How to think about “cure,” “long-term control,” and “recurrence”
Chapter 1 What is cancer? A disease of cells whose brakes are broken
The three key features of cancer cells
Very roughly, cancer is a disease in which cells:
- Lose the “brake” that prevents them from growing too much
- Lose the built-in self-destruct program (apoptosis)
- Invade surrounding tissue, blood vessels, and lymphatic vessels and can spread throughout the body
Normally, our cells obey strict rules:
- they divide only when necessary
- they die when they become old or damaged
- they respect boundaries with neighboring cells
These rules are governed by our genes.
When genes are damaged again and again — by tobacco, UV light, chronic inflammation, viruses, or sometimes just random copying errors — the brakes and self-destruct switches can fail. Then we get cells that:
- keep dividing
- resist dying
- push into neighboring tissue
A lump made of such cells is what we call a malignant tumor — a cancer.
There are two broad categories of tumors:
- benign tumors: grow slowly, do not infiltrate deeply, and do not metastasize
- malignant tumors: infiltrate surrounding tissues and can spread (metastasize) to lymph nodes and distant organs
In everyday language, “cancer” usually refers to malignant tumors.
In Japan and many other countries, over a million new cancers are diagnosed every year. Thanks to advances in screening, surgery, radiotherapy, and drugs, the image of cancer has shifted from “almost always fatal” to “often curable if found early enough.”
Chapter 2 Stage, grade, and subtype: different “faces” of the same cancer
Even if two people both have “breast cancer” or “stomach cancer,” their disease can behave very differently depending on:
- stage: how far it has spread in the body
- grade: how aggressive the cells look under the microscope
- molecular subtype: which receptors and mutations the cancer cells carry
Stage – how far has the cancer spread?
For many solid tumors, doctors use the TNM system:
- T (Tumor): size and local extent of the primary tumor
- N (Nodes): whether lymph nodes are involved, and to what extent
- M (Metastasis): whether there is spread to distant organs
These are then combined into stages:
- Stage I: very early, limited to the organ
- Stage II: larger or deeper, but no distant metastasis
- Stage III: more extensive local spread and/or lymph node involvement
- Stage IV: spread to distant organs such as liver, lung, bone, or brain
Even within one cancer type, prognosis changes dramatically by stage. For example, in early-stage stomach cancer, endoscopic resection or surgery can often aim for cure, whereas Stage IV stomach cancer is usually treated with systemic therapy to control disease and symptoms rather than complete eradication.
Grade – how “wild” do the cells look?
Under the microscope, some tumors look relatively similar to normal tissue and divide slowly. Others look very abnormal and divide extremely fast.
- low-grade tumors: closer to normal cells, slower growth
- high-grade tumors: very abnormal, highly proliferative
In brain tumors and lymphomas, for instance, grade is a major determinant of prognosis.
Molecular subtype – the “wiring” and “switches” of the cancer cell
Molecular subtype refers to the receptors and genetic changes that shape the biology of the tumor.
In breast cancer, for example, we routinely test:
- estrogen receptor (ER)
- progesterone receptor (PR)
- HER2
Based on these, we classify tumors as:
- hormone receptor–positive / HER2-negative
- HER2-positive
- triple-negative (ER-, PR-, HER2-)
These subtypes differ in:
- which drugs are effective
- typical patterns and timing of recurrence
In lung cancer, mutations in EGFR, ALK, ROS1, KRAS and others are key: they determine whether targeted therapies are likely to be effective.
In other words, “what kind of cancer” is only the first layer. “At what stage,” “how aggressive,” and “which subtype” strongly influence how treatable it is.
Chapter 3 Survival in cancer: a bird’s-eye view
Overall 5-year survival has improved
Population-based data show that the 5-year relative survival rate for all cancers combined has risen to roughly the 60% range in many high-income countries.
Compared to the era when cancer was almost uniformly fatal, this means that more than half of people diagnosed with cancer today are alive five years later. That is a major shift.
Differences by cancer type
Very roughly, we can group cancers as follows (assuming appropriate, timely treatment):
Relatively favorable group (especially when detected early)
- breast cancer
- thyroid cancer
- prostate cancer
- uterine (endometrial) cancer
- testicular germ cell tumors
These can have 5-year survival rates exceeding 90% in early stages, making cure a realistic goal.
Intermediate group – prognosis strongly depends on stage
- stomach (gastric) cancer
- colorectal cancer
- non-small-cell lung cancer
- cervical cancer
If detected at Stage I–II, many patients can be cured. At Stage III–IV, survival drops, and the focus may shift toward long-term control.
Difficult-to-treat group (“hard-to-cure” cancers)
- pancreatic cancer
- bile duct and gallbladder cancers (biliary tract cancers)
- some primary liver cancers
- high-grade malignant brain tumors (e.g., glioblastoma)
- small-cell lung cancer
In these cancers, even with modern therapy, reported 5-year survival rates are often in the single digits to teens. They are therefore called “refractory” or “difficult-to-treat” cancers.
However, there is another important truth: when pancreatic cancer is caught at the very earliest stages (so-called Stage 0 or I), some studies report 5-year survival rates in the 60–80% range.
So, beyond “which cancer type,” “at what stage was it found?” is often the single most decisive factor.
Chapter 4 The three classic pillars and where newer treatments fit
The backbone of cancer treatment is still:
- surgery
- radiotherapy
- systemic therapy (drug treatment)
Over the last decade, these have been joined and reshaped by:
- immune checkpoint inhibitors
- molecular targeted therapies
- high-precision radiotherapy
- particle beam therapies (proton and heavy-ion)
- BNCT (boron neutron capture therapy)
- photoimmunotherapy / near-infrared photoimmunotherapy
Surgery – physically removing the tumor
For many solid tumors (stomach, colon, breast, lung, uterus, pancreas, etc.), surgery is the main curative option when the disease is still localized.
- Early cancers may be removed via endoscopy or minimally invasive surgery
- Laparoscopic and robotic approaches aim to reduce pain and recovery time while maintaining precision
Radiotherapy – using invisible beams to damage cancer DNA
Radiotherapy uses X-rays, electron beams, or other forms of radiation to damage the DNA of cancer cells so they can no longer divide.
- In some cancers (prostate, head and neck, early lung cancer, cervical cancer), radiotherapy can be used with curative intent
- It is also crucial in palliative care — for example, to relieve pain from bone metastases
Techniques like IMRT (intensity-modulated radiotherapy) and stereotactic body radiotherapy (SBRT) make it possible to deliver high doses to the tumor while sparing surrounding normal tissues.
Systemic therapy – from classic chemotherapy to targeted and ADCs
“Chemotherapy” today includes several different classes of drugs:
- traditional cytotoxic agents (classic chemotherapy)
- molecular targeted drugs (aimed at specific pathways or mutations)
- hormone therapies (e.g., for breast and prostate cancer)
- antibody–drug conjugates (ADCs)
The optimal sequence and combination of these depend heavily on the tumor’s type and molecular profile, and on whether the goal is cure, disease control, or symptom relief.
Immune checkpoint inhibitors – releasing the brakes on the immune system
Immune checkpoint inhibitors (e.g., nivolumab, pembrolizumab) block molecules such as PD-1/PD-L1 or CTLA-4 that act as “brakes” on T-cells. By releasing these brakes, they can help the immune system recognize and attack cancer cells again.
They have improved survival in a variety of cancers, including:
- non-small-cell lung cancer
- melanoma
- kidney cancer
- some gastric and esophageal cancers
- classical Hodgkin lymphoma
They do not work for everyone, and they bring their own side-effects, but over a 20–30 year time frame they clearly represent a major shift in cancer therapy.
New modalities – combining physical energy and biological targeting
Newer techniques such as:
- high-precision radiotherapy (IMRT, SBRT)
- proton and heavy-ion therapy
- BNCT (boron neutron capture therapy)
- photoimmunotherapy (near-infrared light activating antibody conjugates)
share a basic idea: deliver energy or a reaction very precisely to where cancer cells are, while minimizing damage elsewhere.
In this series, Parts 3–6 will take a deeper look at these modalities one by one.
Chapter 5 What “easier-to-cure” cancers tend to have in common
Rather than memorizing survival percentages by cancer type, it is more useful to notice the shared features of cancers that are relatively easier to cure.
Point 1 – They are more likely to be found early
Examples:
- breast cancer (mammography, ultrasound)
- colorectal cancer (fecal occult blood testing and colonoscopy)
- cervical cancer (Pap smear, HPV testing)
Because these cancers can be detected in a pre-cancerous or very early stage through screening, many patients can start treatment while the disease is still localized.
Point 2 – There are multiple effective treatment options
In breast cancer, prostate cancer, and some blood cancers:
- surgery, radiotherapy, systemic therapy, and hormone therapy can all play roles
- there are multiple effective drugs, including targeted therapies
This means that if one regimen stops working, there may be other options — enabling long-term survival for many patients.
Point 3 – The tumor biology is relatively indolent
Cancers with:
- slower growth
- lower tendency to metastasize
- lower histological grade
tend to allow more time and flexibility in treatment planning. Examples include some thyroid cancers and low-grade brain tumors.
Chapter 6 What “hard-to-cure” cancers have in common
On the other side, “difficult-to-treat” or “refractory” cancers often share several obstacles.
Barrier 1 – Few symptoms until the disease is advanced
Pancreatic and biliary tract cancers, for example, often present with:
- vague abdominal discomfort
- loss of appetite or weight
- back pain or fatigue
Symptoms that are easily attributed to more benign problems. Screening tests that reliably catch these cancers at very early stages are still under development. As a result, many patients are diagnosed at Stage III–IV.
Barrier 2 – Anatomically challenging locations
The pancreas and bile ducts are surrounded by:
- major blood vessels
- liver, stomach, and duodenum
This makes both extensive surgery and high-dose radiotherapy technically and functionally difficult.
For malignant brain tumors such as glioblastoma, the issue is even more fundamental: we cannot simply remove large portions of brain tissue. Even with maximal safe resection, microscopic tumor cells almost always remain.
Barrier 3 – Very fast growth and early spread
Small-cell lung cancer and glioblastoma are classic “sprinters”:
- they often respond well at first to chemotherapy and radiotherapy
- but they tend to recur quickly once treatment stops
Even short breaks in therapy can allow the tumor to regrow and spread.
Barrier 4 – Limited drug options or limited drug effect
Although research is advancing, for some cancers:
- truly effective targeted drugs are still few
- the tumor’s genetic diversity makes it hard for a single drug to work broadly
- resistance tends to develop rapidly
These biological and therapeutic constraints together contribute to the “hard-to-cure” label.
In Parts 7 and 8 of this series, we will look at these cancers individually — pancreatic, biliary, liver, ovarian cancer, glioblastoma, small-cell lung cancer, and others — and discuss:
- typical clinical courses
- current standard of care
- where new therapies and clinical trials are heading
Chapter 7 What does “recurrence” really mean?
Cancer can appear again after a period of remission. Clinically we often categorize recurrence as:
- local recurrence – return of cancer in the same area
- regional recurrence – in nearby lymph nodes
- distant metastasis – in organs such as liver, lungs, bone, or brain
Why does this happen?
- Microscopic cancer cells may have remained even after surgery and were invisible on imaging
- The first treatment may have killed the more sensitive cells, leaving behind resistant clones that later regrew
- In some organs (like liver or head and neck), new primary cancers can arise on a background of chronic damage or carcinogenic exposure
ctDNA and MRD – trying to detect leftover “embers”
A rapidly evolving area of research is the use of circulating tumor DNA (ctDNA) in blood to detect minimal residual disease (MRD).
The aims include:
- detecting remaining cancer cells after supposedly curative treatment
- identifying recurrence earlier than imaging alone
If these approaches become reliable and widely available, they could enable:
- more intensive follow-up and adjuvant therapy for patients at high risk of recurrence
- de-escalation of treatment for those at clearly low risk
In other words, they could help tailor treatment intensity much more precisely.
Chapter 8 Between “5-year survival” and “cure”
Common misunderstandings about 5-year survival
People often interpret statistics like this:
- “High 5-year survival = everyone is cured”
- “Low 5-year survival = no one lives beyond 5 years”
Both are wrong.
5-year survival is a summary of how a large group of patients did in the past, not a prediction carved in stone for one individual.
In real life:
- some patients with “good-prognosis” cancers do unfortunately relapse
- some patients with “poor-prognosis” cancers live much longer than average
When doctors talk about prognosis, they are blending:
- statistical trends
- the patient’s age, performance status, and other illnesses
- stage, grade, and molecular subtype of the tumor
- response (or lack of response) to initial treatment
Different cancers, different timelines for “near-cure”
In some cancers, if there is no recurrence within around 5 years, the risk becomes very low, and many doctors and patients feel reasonably “safe.” Examples include some colorectal and early breast cancers.
In others:
- hormone-driven cancers (such as some breast and prostate cancers) can relapse even 10 years or more after the initial diagnosis, so prolonged follow-up is needed
- in liver cancer or some head and neck cancers, new tumors can arise in the same organ over time, so periodic surveillance remains important
This is why follow-up schedules and the moment when a doctor says “you are almost certainly cured” vary from cancer to cancer.
Chapter 9 What this series aims to provide
In everyday oncology practice, doctors and patients are constantly navigating different goals:
- aiming for cure whenever realistically possible
- aiming for long-term disease control when cure is unlikely
- prioritizing symptom relief and quality of life when disease is very advanced
For patients and families to participate in decisions that align with their values, it helps enormously to have a rough mental map of:
- what treatments exist
- what each treatment can and cannot do
- why doctors make certain recommendations
This Introductory–to–Basic Series on Cancer Treatment is designed to support that.
The planned structure is:
- Part 1: overall landscape and the idea of “easier” vs “harder” cancers (this article)
- Part 2: roles of surgery, systemic therapy, and immunotherapy, and why recurrence happens
- Part 3: basics of radiotherapy (X-rays, IMRT, SBRT)
- Part 4: proton and heavy-ion therapy – when and why they are used
- Part 5: BNCT (boron neutron capture therapy) – basic principles and current indications
- Part 6: photoimmunotherapy – concept and current use in head and neck cancer and beyond
- Part 7: case studies in difficult cancers I (pancreatic, biliary, liver cancers)
- Part 8: case studies in difficult cancers II (ovarian cancer, glioblastoma, small-cell lung cancer, etc.)
In the next article (Part 2), we will dig deeper into:
- how surgery, chemotherapy, targeted drugs, and immunotherapy complement each other
- in more detail, why and how recurrence occurs
This article was edited by the Morningglorysciences team.
The content is for general informational purposes only and is not a substitute for individual medical advice. For decisions about diagnosis or treatment, please always consult your treating physician.
Comments