RARE CANCER TREATMENTS
A COMPLETE PATIENT GUIDE

Rare cancers are defined as those with an incidence below 6 cases per 100,000 population per year. Collectively, they account for 20–25% of all cancer diagnoses and 25% of cancer mortality — a major public health burden hidden behind statistical rarity.

“The paradox: each rare cancer is uncommon, but together they are one of the most significant cancer problems in the world.”

• The Numbers

  Europe diagnoses ~500,000 rare cancer cases annually. The US NCI defines rare cancers as fewer than 40,000 cases/year. Despite each being individually uncommon, collectively they rival the most common cancer types in total impact.

• What Makes a Cancer Rare

  Rarity can arise from the organ involved (appendix, adrenal cortex), the specific histological subtype (adenoid cystic carcinoma), the molecular profile (rare KRAS mutation variant), or the inherent biology of the disease (mesothelioma, pseudomyxoma peritonei).

• Ultra-Rare Cancers

  A subset with incidence below 1 per 100,000/year — includes many sarcoma subtypes, adrenocortical carcinoma, Merkel cell carcinoma, and primary CNS lymphoma. These patients face the most extreme evidence gaps and fewest available trials.

• The Shared Experience

  Rare cancer patients share not biology but circumstance: an oncologist who has rarely treated their cancer, limited online information, no nearby trial, and treatment based on similar-but-not-identical cancer protocols.

Rare cancers face structural disadvantages in every dimension of oncology: evidence, diagnosis, treatment infrastructure, and clinical trial access. Understanding these gaps is the first step in navigating them.

• The Evidence Gap

  Randomised trials require large populations. A cancer affecting 2 per 100,000 may yield only hundreds of patients per continent annually — making definitive RCTs impossible. Treatment decisions are based on lower-quality evidence, case series, and expert consensus.

• Diagnostic Delay

  Rare cancer symptoms are non-specific and mimic benign conditions. Diagnosis can take months to years. Correct histological classification requires specialist pathology concentrated at a few centres globally — misdiagnosis is documented and clinically consequential.

• Treatment at Non-Specialist Centres

  Most rare cancer patients receive care at general oncology centres. High-volume specialist centres consistently demonstrate better outcomes — not from physician talent alone, but from accumulated experience and multidisciplinary infrastructure.

• Clinical Trial Access Barrier

  For common cancers, multiple nearby trials exist. For rare cancers, one relevant global trial may exist — located abroad, requiring specific molecular eligibility, or closed due to slow accrual. The patients who need trials most face the greatest access barriers.

Rare cancers span every organ system. Knowing the major categories helps patients identify relevant expertise, treatment approaches, and trial opportunities.

• Sarcomas

  Cancers of connective tissue — bone, muscle, fat, nerve sheath, vasculature. 100+ distinct subtypes including GIST, liposarcoma, leiomyosarcoma, synovial sarcoma. Require specialist sarcoma multidisciplinary teams.

• Rare Haematological Malignancies

  Waldenström macroglobulinaemia, hairy cell leukaemia, angioimmunoblastic T-cell lymphoma, systemic mastocytosis — each requiring unique investigation and therapy distinct from common blood cancers.

• Rare CNS Tumours

  Primary CNS lymphoma, adult medulloblastoma, ependymoma, pineoblastoma, CNS germ cell tumours. Treatment requires specialist neuro-oncology, advanced neurosurgery, radiosurgery, and often proton beam therapy.

• Rare Endocrine Tumours

  Adrenocortical carcinoma, phaeochromocytoma, paraganglioma, anaplastic thyroid carcinoma, and NETs — ranging from indolent Grade 1 to highly aggressive Grade 3 neuroendocrine carcinomas.

• Rare Gynaecological Cancers

  Uterine sarcomas (leiomyosarcoma, ESS), clear cell ovarian carcinoma, vaginal/vulvar carcinoma, gestational trophoblastic disease — each with unique treatment protocols separate from common gynaecological cancers.

• Rare GI Cancers

  Cholangiocarcinoma, gallbladder cancer, small intestine cancer, appendiceal cancer, anal canal SCC, pseudomyxoma peritonei, GI NETs. Cholangiocarcinoma has rapidly expanding actionable targets (FGFR2, IDH1, BRAF).

Twelve rare cancers most frequently encountered among international CancerFax patients — with key molecular targets and treatment approaches.

For rare cancers, comprehensive molecular profiling is not optional — it is often the only way to identify an actionable target and access a relevant therapy or trial. Standard histology alone is insufficient.

“In rare cancers, what the tumour looks like is less important than what it is driven by at the molecular level.”

• Next-Generation Sequencing (NGS)

  Comprehensive genomic profiling panels (e.g., FoundationOne CDx, Tempus, Guardant) identify hundreds of mutations, fusions, and copy number changes simultaneously — revealing targetable alterations standard testing misses.

• RNA Sequencing for Fusion Detection

  Many sarcomas and rare carcinomas are defined by characteristic gene fusions (EWSR1 in Ewing, SS18-SSX in synovial sarcoma, FGFR2 fusions in cholangiocarcinoma). RNA sequencing or fusion-specific panels are required for accurate classification.

• IHC and Biomarker Panels

  Immunohistochemistry for MSI/MMR status, PD-L1 expression, HER2, ALK, ROS1, and tumour mutational burden (TMB) identifies candidates for immunotherapy and targeted drugs in rare cancers where no specific agent is approved.

• Re-Biopsy and Liquid Biopsy

  Rare cancers evolve under treatment pressure. Re-biopsy at progression — or liquid biopsy (ctDNA) — identifies resistance mechanisms and new actionable alterations, enabling treatment adaptation unavailable without molecular re-assessment.

Tumour-agnostic therapies are approved based on a molecular biomarker — not the tumour's tissue of origin. For rare cancer patients, these are the most important therapeutic advances in decades.

• MSI-H / dMMR — Pembrolizumab

  Approved for any MSI-H/dMMR solid tumour regardless of origin. Highly actionable in rare GI tumours, endometrial sarcoma, and other rare cancers that would otherwise have no immunotherapy approval.

• NTRK Fusion — Larotrectinib / Entrectinib

  NTRK fusions occur in ~1% of common cancers but at higher rates in certain rare cancers (secretory carcinoma, infantile fibrosarcoma, mammary analogue secretory carcinoma). 75%+ response rates regardless of histology.

• High TMB — Pembrolizumab

  Approved for TMB-H (≥10 mut/Mb) solid tumours. Rare cancers with high mutational burden from repair defects or other mechanisms can access pembrolizumab without cancer-type-specific trial data.

• RET Fusion — Selpercatinib / Pralsetinib

  Tumour-agnostic approval for RET fusion-positive solid tumours. Relevant to rare pancreatic cancers, cholangiocarcinoma, and other rare carcinomas with RET fusions identified on NGS.

• 20–25%of all cancers are rare cancersCollectively a major public health problem despite individual rarity.
• <25%of rare cancer patients have access to a relevant clinical trialTrial access is the most critical unmet need for rare cancer patients globally.
• 75%+response rate for NTRK fusion-positive cancers with larotrectinibTumour-agnostic therapies deliver dramatic results regardless of histology.
• 100+sarcoma subtypesSarcomas alone encompass over 100 distinct diagnoses, each with unique biology and treatment.

For many rare cancer patients, a clinical trial is not just a research option — it is the most advanced treatment available. Basket trials, umbrella trials, and molecular matching platforms have transformed rare cancer trial access.

• Basket Trials

  Enrol patients based on a shared molecular alteration across multiple cancer types. NCI-MATCH, TAPUR, MyPathway — these trials specifically benefit rare cancer patients who share a molecular target with more common cancers.

• Umbrella Trials

  Umbrella studies for rare histologies (sarcoma, NET, carcinoma of unknown primary) allow multiple sub-studies within one trial framework, enabling meaningful patient numbers for rare cancer subtypes.

• International Trial Access

  For ultra-rare cancers, the only relevant open trial may be in another country. CancerFax actively identifies enrolling trials globally — including China, which has one of the world's most active oncology trial ecosystems — and facilitates eligibility assessment and access.

Rare cancer patients need more than a referral — they need navigation through a fragmented, specialist-dependent system.

1. 1

   Medical Record & Pathology Review

   Comprehensive review of pathology, molecular reports, and treatment history to identify the exact rare cancer subtype and any actionable molecular alterations.

2. 2

   Molecular Profiling Guidance

   Identification of the most appropriate NGS or biomarker panel if not yet done, and interpretation of existing molecular results in the context of treatment options and trial eligibility.

3. 3

   Specialist Centre Matching

   Identification of the highest-volume specialist centre for the specific rare cancer type globally — including sarcoma centres, NET specialist centres, and rare cancer reference centres in China, Europe, and beyond.

4. 4

   Clinical Trial Identification

   Active search of global trial databases for enrolling basket, umbrella, and histology-specific trials relevant to the patient's molecular profile and cancer type.

5. 5

   Travel & Logistics

   Medical visa, travel, accommodation, and in-country support for patients travelling to specialist centres abroad.

6. 6

   Second Opinion Facilitation

   Coordination of remote or in-person second opinions with specialist rare cancer oncologists at leading reference centres — often revealing treatment options not identified at the initial treating centre.

Each page covers one rare cancer topic in depth.

Frequently Asked Questions