1. Follow-up
As of September 30, 2021, all 85 patients were followed up for ≥ 6 months. The local control status of the patients at six months after seed implantation was as follows: 27 (31.76%) achieved CR, 33 (38.82%) achieved PR, 16 (18.82%) showed SD, and 9 (10.59%) showed PD. The CR rate was 31.76% (27/85), the overall response rate was 70.59% (60/85), and the disease control rate was 89.41% (76/85).
2. Clinical efficacy and analysis
2.1 For patients with lung cancer, the postoperative dose D90 in the CR group was 138.70 ± 19.14 Gy, while in the non-CR group (PR + SD + PD), it was 118.33 ± 28.62 Gy. The difference in postoperative dose D90 between the CR group and the non-CR group was statistically significant (t = 2.34, P = 0.024). For patients with metastatic lung cancer, the postoperative dose D90 in the CR group was 151.33 ± 41.49 Gy, while in the non-CR group (PR + SD + PD), it was 116.76 ± 25.90 Gy. The difference in postoperative dose D90 between the CR and non-CR groups was statistically significant (t = 2.95, P = 0.006). There was no statistically significant difference in the postoperative D90 between the CR group of patients with lung cancer and the CR group of patients with metastatic lung cancer (t = 0.99, P = 0.335). Similarly, there was no statistically significant difference in the postoperative D90 between the non-CR group of patients with lung cancer and the non-CR group of patients with metastatic lung cancer (t = 0.2, P = 0.839) (Table 2).
Table 2
Comparison of postoperative D90 dose between the complete response (CR) group and the non-CR group for lung tumors originating from different types of primary cancers
Primary disease origin | CR group D90 (Gy) | Non-CR group D90 (Gy) | t | P |
Lung cancer | 138.70 ± 19.14 | 118.33 ± 28.62 | 2.34 | 0.024 |
Lung metastases | 151.33 ± 41.49 | 116.76 ± 25.90 | 2.95 | 0.006 |
Lung cancer CR vs metastatic CR | | | 0.99 | 0.335 |
Lung cancer non-CR vs metastatic non-CR | | | 0.2 | 0.839 |
When we combined the CR group patients with lung cancer and metastatic lung cancer and compared them with the non-CR group patients with lung cancer and metastatic lung cancer, we observed a statistically significant difference in D90 between the combined CR and non-CR groups (t = 3.94, P = 0.00; Table 3). The optimal thresholds for postoperative D90 and the CR rate were obtained by creating an ROC curve, with an area under the curve of 0.749. The maximum Youden index corresponded to a postoperative D90 of 140.46 Gy (Fig. 1). When comparing groups based on a postoperative D90 cutoff of 140 Gy, the CR rates for the D90 ≥ 140 Gy and D90 < 140 Gy groups were 60.71% (17/28) and 17.54% (10/57), respectively, and the difference was statistically significant (χ2 = 16.14, P = 0.0001; Table 4).
Table 3
Comparison of postoperative D90 dose between the combined complete response (CR) and non-CR groups
Primary disease origin | Combined CR group D90 (Gy) | Combined non-CR group D90 (Gy) | t | P |
Lung cancer + lung metastases | 145.25 ± 33.30 | 117.77 ± 27.67 | 3.94 | 0.00 |
Table 4
Comparison of CR and non-CR patients based on a postoperative D90 cutoff of 140 Gy
Postoperative D90 | CR | non-CR | Rate(%) | χ2 | P |
<140Gy group | 10 | 47 | 17.54 | 16.14 | 0.0001 |
≥ 140Gy group | 17 | 11 | 60.71 |
2.2 Analysis of the correlation between postoperative local control and clinical characteristics
In this study, we categorized general patient information, tumor histopathological classification, the tumor microenvironment, and treatment into seven clinicopathological factors and performed univariate analysis to examine their associations with the postoperative CR rate six months after seed therapy. The results showed that both tumor size (χ2 = 16.28, P = 0.0001) and postoperative D90 (χ2 = 16.14, P = 0.0001) significantly influenced the effectiveness of seed therapy (Table 5). However, age, sex, pathological type, preoperative hemoglobin level, and whether combined treatment was administered did not significantly differ. When factors such as tumor size, postoperative D90, and whether combined treatment was administered were included in a binary logistic analysis, tumor size (P = 0.0003) and postoperative D90 (P = 0.0005) were found to be independent prognostic factors for postoperative CR.
Table 5
Univariate analysis of the postoperative 6-month complete response rate in 85 patients with seed pulmonary tumors treated with seed therapy
Characteristic | Cases | CR | Non-CR | Chi-square value | P |
Sex | | | | 1.58 | 0.208 |
Male | 64 | 18 | 46 | | |
Female | 21 | 9 | 12 | | |
Age (y) | | | | | |
< 65 | 41 | 13 | 28 | 0 | 0.991 |
≥ 65 | 44 | 14 | 30 | | |
Preoperative hemoglobin (g/L) | | | 0.08 | 0.775 |
< 120 | 39 | 13 | 26 | | |
≥ 120 | 46 | 14 | 32 | | |
Pathological type | | | 1.51 | 0.219 |
Carcinoma | 77 | 26 | 51 | | |
Sarcoma | 8 | 1 | 7 | | |
Tumor size (cm) | | | | 16.28 | 0.0001 |
< 4 | 42 | 22 | 20 | | |
≥ 4 | 43 | 5 | 38 | | |
Postoperative D90 (Gy) | | | | 16.14 | 0.0001 |
< 140 | 57 | 10 | 47 | | |
≥ 140 | 28 | 17 | 11 | | |
Combined treatment | | | 0.19 | 0.663 | |
Yes | 47 | 14 | 33 | | |
No | 38 | 13 | 25 | | |
2.3 Complications
Among the patients who underwent seed implantation, 43 had pneumothorax, accounting for 51.4% (43/85) of the total cases. Of these, 12 patients were classified as having small pneumothorax, which resolved spontaneously without symptomatic intervention. For the remaining 31 patients, closed thoracic drainage was performed, and the drainage tube was removed after three days. Bleeding was reported in three patients: two with pulmonary bleeding and one with hemoptysis. Symptomatic hemostasis was administered, and relief was achieved within two days. Additionally, there was one case of subcutaneous hematoma, which resolved on its own within two days. No significant pain, tumor implantation metastasis, air embolism, or radiation pneumonitis was observed postoperatively.