Background: Esophageal cancer is associated with synchronous or metachronous cancer at other primary sites. However, few studies have evaluated the second malignancies after the treatment of esophageal cancer. The present study aimed to clarify the frequency of and risk factors for the second malignancies after definitive therapy for esophageal cancer.Patients and Methods: We included patients with esophageal cancer who received definitive therapy between 2000 and 2010. Exclusion criteria were synchronous cancer or a past history of cancer. Standardized incidence rate (SIR) was calculated using age‐ and sex‐specific incidence rates from the cancer registry data. To conduct risk analyses, we used the competing risk regression model, which defined death and the development of second malignancies as competing risks.Results: A total of 758 patients were included, with 131 second malignancies occurring in 106 patients (14%), over a median follow‐up of 3.7 years. Cumulative incidences of second malignancies after 3, 5, and 8 years were 4.0%, 7.6%, and 13.8%, respectively. The risk of second malignancy was significantly elevated [SIR = 1.83, 95% confidence interval (CI): 1.50‐2.22]. The most common sites of primary tumor were the head and neck (20%), followed by the lung (17%), stomach (16%), colon and rectum (11%), and urinary tract (9%). Risk analyses revealed that age ≥ 65 years [subdistribution hazard ratio (sHR): 1.51, 95% CI: 1.01‐2.24, vs age < 65] and clinical stages 0‐I (sHR: 2.48, 95% CI: 1.46‐4.22, vs stage III and IV) and II (sHR: 2.10, 95% CI: 1.23‐3.58, vs stage III and IV) were significantly associated with second malignancies.Conclusions: Compared with the general population, an increased incidence of second malignancies was observed in the patients with esophageal cancer in the present study even after definitive treatment. Careful follow‐up is required, especially in patients at a higher risk of second malignancies.

Background: Abdominal/pelvic lymph node (LN) oligometastasis, a pattern of treatment failure, is observed occasionally, and radiotherapy may work as salvage therapy. The optimal prescription dose, however, is yet to be determined. This study assessed the efficacy of high-dose radiotherapy. Methods: The medical records of 113 patients at 4 institutes were retrospectively analysed who had 1 to 5 abdominal/pelvic LN oligometastases and were treated with definitive radiotherapy between 2008 and 2018. The exclusion criteria included non-epithelial tumours, uncontrolled primary lesions, palliative intent, and re-irradiation. The prescription dose was evaluated by using the equivalent dose in 2 Gy fractions (EQD2). Patients receiving EQD2 ≥ 60 Gy were placed into the high-dose group, and the remaining others the low-dose group. Kaplan-Meier analyses were performed to evaluate overall survival (OS), local control (LC), and progression-free survival (PFS). Univariate log-rank and multivariate Cox proportional hazards model analyses were performed to explore predictive factors. Adverse events were compared between the high-dose and low-dose groups. Results: The primary tumour sites included the colorectum (n = 28), uterine cervix (n = 27), endometrium (n = 15), and ovaries (n = 10). The rate of 2-year OS was 63.1%, that of LC 59.7%, and that of PFS 19.4%. On multivariate analyses, OS were significantly associated with solitary oligometastasis (hazard ratio [HR]: 0.48, p = 0.02), LC with high-dose radiotherapy (HR: 0.93, p < 0.001), and PFS with long disease-free interval (HR: 0.59, p = 0.01). Whereas high-dose radiotherapy did not significantly improve 2-year OS in the entire cohort (74.8% in the high-dose vs. 52.7% in the low-dose; p = 0.08), it did in the subgroup of solitary oligometastasis (88.8% in the high-dose vs. 56.3% in the low-dose; p = 0.009). As for Late grade ≥ 3 adverse event, ileus was observed in 7 patients (6%) and gastrointestinal bleeding in 4 (4%). No significant association between the irradiation dose and adverse event incidence was found. Conclusions: As salvage therapy, high-dose radiotherapy was recommendable for oligometastasis in the abdominal/pelvic LNs. For solitary oligometastasis, LC and OS were significantly better in the high-dose group.

Deep inspiration breath-hold (DIBH) is widely used to reduce the cardiac dose in left-sided breast cancer radiotherapy. This study aimed to develop a deep learning chest X-ray model for cardiac dose prediction to select patients with a potentially high risk of cardiac irradiation and need for DIBH radiotherapy. We used 103 pairs of anteroposterior and lateral chest X-ray data of left-sided breast cancer patients (training cohort: n = 59, validation cohort: n = 19, test cohort: n = 25). All patients underwent breast-conserving surgery followed by DIBH radiotherapy: the treatment plan consisted of three-dimensional, two opposing tangential radiation fields. The prescription dose of the planning target volume was 42.56 Gy in 16 fractions. A convolutional neural network-based regression model was developed to predict the mean heart dose (∆MHD) reduction between free-breathing (MHD_FB) and DIBH. The model performance is evaluated as a binary classifier by setting the cutoff value of ∆MHD > 1 Gy. The patient characteristics were as follows: the median (IQR) age was 52 (47–61) years, MHD_FB was 1.75 (1.14–2.47) Gy, and ∆MHD was 1.00 (0.52–1.64) Gy. The classification performance of the developed model showed a sensitivity of 85.7%, specificity of 90.9%, a positive predictive value of 92.3%, a negative predictive value of 83.3%, and a diagnostic accuracy of 88.0%. The AUC value of the ROC curve was 0.864. The proposed model could predict ∆MHD in breast radiotherapy, suggesting the potential of a classifier in which patients are more desirable for DIBH.