Invasive thymoma - Which patients benefit from post-operative radiotherapy?

BACKGROUND

The aim of this study is to identify patients with thymoma who should receive post-operative radiotherapy.

METHODS

The Surveillance, Epidemiology, and End Results database was queried for stage IIB-IV thymoma patients diagnosed during 1988-2015. We analyzed the prognostic implications of various clinical-pathological factors by comparing the outcomes of those who received surgery with and without post-operative radiotherapy.

RESULTS

A total of 1120 patients were identified; 62% received post-operative radiotherapy and 38% underwent surgery alone. In a propensity-matched cohort of 812 patients, no survival difference was seen in World Health Organization A, AB, B1, B2, or B3 tumors with the addition of post-operative radiotherapy to surgery (p>0.05). Post-operative radiotherapy also did not improve survival over surgery alone for tumors ≥ or < less than the 4 cm, 7 cm, 10 cm, and 13 cm cutoffs, all p>0.05. Post-operative radiotherapy was an independent, positive prognostic indicator only in the subgroup with stage III disease and in those receiving chemotherapy in addition to post-operative radiotherapy, both p<0.05.

CONCLUSIONS

Patients with stage III thymoma are most likely to benefit from the addition of post-operative radiotherapy to surgical treatments. Tumor size or World Health Organization histology alone should not be criteria for determining the need for post-operative radiotherapy in locally advanced thymoma. Masaoka-Koga stage, which has traditionally been used to help make such decisions, appears to be the most reliable determinant of the use of post-operative radiotherapy.

Different View on Tumor Size Dilemma in Tumor-Node-Metastasis Staging System for Thymoma

BACKGROUND

Although tumor size is included in the definition of T descriptor in the tumor-node-metastasis (TNM) classification of many solid tumors, it is not considered for thymomas. This study aimed to assess the relationship of tumor diameters (the largest tumor diameter [LTD] and the mean tumor diameter [MTD]) with survival in thymoma patients undergoing surgical resection in a single center.

METHODS

The study included 127 thymoma patients (age, 49.2 ± 15.2 years; 65 males), who were evaluated based on pathological tumor sizes according to the LTD and MTD ([largest diameter + shortest diameter] / 2) and divided into three subgroups for each parameter as: patients with an LTD of ≤5 cm, 5.1 to 10 cm, and >10 cm and patients with an MTD of ≤5, 5.1 to 10, and >10 cm.

RESULTS

In thymoma patients, survival significantly differed according to the presence of myasthenia gravis (p = 0.018), resection status (R0 or R1; p = 0.001), T status (p = 0.015), and the Masaoka-Koga stage (p = 0.003). In the LTD subgroups, the overall survival of those with R0 resection was lower in those with an LTD of 5.1 to 10 cm than in those with an LTD of ≤5 cm (p = 0.051) and significantly lower in those with an MTD of 5.1 to 10 cm than in those with an MTD of ≤5 cm (p = 0.027). In the MTD subgroups, survival decreased as the tumor size increased.

CONCLUSION

Both smaller tumor size and complete resection are associated with better survival in thymoma patients. Therefore, the largest or the mean tumor size might be considered as a criterion in the TNM staging for thymoma.