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Favourable subsets of cancer of unknown primary are the roughly one in five cases where the pattern of spread, the microscope appearance or blood markers point strongly to a particular cancer even though no primary can be found. They are treated as that cancer would be, for example breast cancer for a woman with cancer only in armpit nodes, and many are curable or controllable for years.
Cancer of unknown primary is a metastatic cancer whose origin cannot be found despite a full work-up. Within it, decades of clinical observation identified subsets that behave like, and respond to treatment for, a specific cancer. The ESMO 2023 guideline lists them: women with adenocarcinoma confined to axillary nodes (treated as breast cancer with axillary dissection, breast radiotherapy or mastectomy and systemic therapy); women with serous papillary carcinoma of the peritoneum (treated as ovarian cancer with cytoreductive surgery and carboplatin-paclitaxel); squamous cell carcinoma in cervical nodes (treated as head and neck cancer, with HPV or EBV testing, neck dissection and chemoradiotherapy) or in inguinal nodes (treated with node dissection and radiotherapy as anogenital cancer); young men with poorly differentiated carcinoma in a midline distribution or raised markers (treated as extragonadal germ cell tumour with cisplatin-based chemotherapy); men with bone metastases and raised PSA (treated as prostate cancer); neuroendocrine carcinoma of unknown primary (treated as extrapulmonary neuroendocrine carcinoma or, if well differentiated, as a neuroendocrine tumour); adenocarcinoma with a colorectal immunoprofile (CK20 and CDX2 positive, CK7 negative; treated as colorectal cancer); a single resectable metastasis (treated with surgery or radiotherapy); and renal-like carcinoma.
Recognising these patterns depends on a disciplined work-up: histology with a directed immunohistochemistry panel, CT of chest, abdomen and pelvis, mammography or breast MRI and gynaecological examination in women, PSA in men, alpha-fetoprotein and hCG in young patients, and PET-CT in cervical node squamous carcinoma and single-site disease. Gene-expression and DNA-methylation tissue-of-origin classifiers can assign a likely primary in most cases, but two randomised trials (GEFCAPI 04 and a Japanese trial) found that classifier-directed site-specific therapy did not beat empirical chemotherapy in unfavourable disease, so the classifiers are used to support rather than replace clinical judgement. Because the subsets are treated as their presumed cancer, their prognosis approaches that of the corresponding metastatic or node-positive disease, which is why every patient with CUP should be reviewed against the list before empirical chemotherapy is started.
About a fifth of cancers of unknown primary fall into a recognised favourable subset; these patients live far longer than the rest because their disease can be treated as the cancer it most resembles.
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Also on OnCo: Symptoms and red flags · Early detection roadmap.
Histology with directed immunohistochemistry, CT of chest, abdomen and pelvis, sex-specific examinations and tumour markers, PET-CT for cervical node squamous carcinoma and single-site disease.
Treat as node-positive breast cancer: axillary dissection, breast radiotherapy or mastectomy, systemic therapy by receptor status.
Treat as advanced ovarian cancer: cytoreductive surgery and carboplatin-paclitaxel with maintenance as indicated.
Treat as head and neck cancer: HPV and EBV testing, neck dissection or chemoradiotherapy with cisplatin.
Treat as extragonadal germ cell tumour with cisplatin-based combination chemotherapy.
Platinum-etoposide as for extrapulmonary neuroendocrine carcinoma; somatostatin analogues and radioligand therapy for well-differentiated tumours.
Resection or stereotactic radiotherapy with curative intent.
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The split between favourable and unfavourable cancer of unknown primary on OnCo, and the treatment on each page, follow this guideline.
Predicting the primary site by gene expression and treating accordingly is not better than empirical chemotherapy, so guidelines do not recommend it; the field moved to genomic profiling for actionable targets instead.
Query for this cancer: (TITLE:"Cancer of unknown primary, favourable subsets" OR ABSTRACT:"Cancer of unknown primary, favourable subsets" OR TITLE:"Favourable-risk CUP" OR ABSTRACT:"Favourable-risk CUP" OR TITLE:"Treatable CUP subsets" OR ABSTRACT:"Treatable CUP subsets" OR TITLE:"CUP with a presumed primary" OR ABSTRACT:"CUP with a presumed primary" OR TITLE:"Specific CUP syndromes" OR ABSTRACT:"Specific CUP syndromes") AND (treatment OR therapy OR trial OR survival OR diagnosis). Results are unfiltered search hits about Cancer of unknown primary, favourable subsets, not a curated reading list.
The targets of this cancer's medicines and the ones linked to it directly.
Cases by country, the UK and NHS pathway and other country lenses, the expert centres with trials on record, and the centres named on this cancer's subtypes.
One section per setting: the options named, what each is for, the trials behind them, the recorded trade-offs and the questions to ask.
Bleeding that does not stop by itself, bleeding from more than one site, or new bruising in several places or one large area.
Sudden severe bone pain, or back pain with weakness or numbness in the legs (possible spinal cord compression).
Dose by Calvert formula using GFR (see the calculators).
Dose reduce or avoid for CrCl below 60 (carboplatin is the alternative).
Reduce to 75% for CrCl 15-50.
During chemotherapy a temperature over 37.5 C or below 36 C, shivering, or feeling unwell even with a normal temperature means ringing the hospital's 24-hour line straight away; breathing very fast, confusion, mottled skin or no urine in a day means 999.
See all on the product pages:CarboplatinCisplatinEtoposideLutetium-177 dotatatePaclitaxel / nab-paclitaxelPlatinum + etoposide (EP / CE)·Printable cards in the navigator
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Everything in development, the medicines held by this cancer's subtypes, the open problems and what is being done about them, the roadmaps, and what changed on this record.
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