Thymic tumours are rare and surgical resection forms the mainstay of treatment.
Thymoma (A, AB, B1-3)
Management is mostly dictated by the stage of presentation and the aggressiveness of the tumour.
- Stage I and II tumours should be resected surgically.
- Stage III tumours should have surgery followed by adjuvant radiotherapy and/or chemotherapy
- Stage IV tumours are often unresectable and are treated with systemic therapy; local measures to reduce symptoms in the chest are possible.
Surgery
Surgery aims to remove the thymus and surrounding fat together with the tumour mass. Complete surgical resection is usually possible for stage I and II thymomas (confined to the gland or invading adjacent fat only). Debulking surgery is recommended for stage III and IV disease as adjuvant radiotherapy may be able to sterilise the remaining disease more easily than the complete tumour mass.
Radiotherapy Alone
Inoperable patients may still benefit from radical radiotherapy, although there are no standardised trials to guide therapy decisions. Doses as high as 60 Gy have been used.
Chemoradiotherapy Alone
I couldn't find any data on this; I presume it could be offered for unresectable patients
Adjuvant Therapy
Adjuvant Radiotherapy
Adjuvant radiotherapy is used for:
- Positive margins (45 Gy)
- Gross residual disease (55-60 Gy)
- High risk disease (Stage III+)
Adjuvant treatment for completely resected stage II disease is controversial and recent meta-analysis has demonstrated no benefit. It could be considered for higher risk stage II disease (eg. B2 or B3 thymoma). Meta-analysis in thymoma is complicated by the long periods over which data is collected and changes in practice.
Adjuvant Chemotherapy
Numerous schedules are described. Platinum drugs are the main backbone of treatment and combined chemotherapy schedules often show good response. Chemotherapy is typically employed for high risk disease (stage III/IV).
Neoadjuvant Therapy
Numerous case series report good rates of resectability following neoadjuvant therapy. This approach has not been studied systemically but one retrospective report trialled combined chemoradiotherapy (carboplatin/etoposide + RT) which allowed for improved rates of surgical resection.
Thymic Carcinoma
Thymic carcinomas (Grade C) are highly malignant tumours that are extensively invasive, metastasise and frequently recur.
- Surgical resection remains the most important aspect of therapy
- Adjuvant radiotherapy is almost always recommended; doses from 50.4 Gy/28# (adjuvant) to 60 Gy (large residual) are typically used depending on the amount of residual disease
- Adjuvant chemotherapy is commonly recommended, usually with a cisplatin or carboplatin combination regiment (eg. carbo/etoposide)
- Unresectable cases should receive neoadjuvant chemotherapy followed by surgery if possible or definitive radiotherapy (60 Gy/30#) if surgery is not feasible
Thymic Carcinoid
These tumours represent 5% of anterior mediastinal masses. Unlike other carcinoids they are highly aggressive and frequently metastasise. There is even less evidence for treatment of these tumours. Surgery again forms the main treatment if feasible. Adjuvant therapies are thought to reduce local recurrence.