ESTRO 2021 Abstract Book

S686

ESTRO 2021

the femoral vessels to cover 95% of the nodes for supra IPS region in anterior, medial and lateral directions was 29 mm, 23 mm and 21 mm respectively and for infra IPS region in anterior and medial directions was 21 mm and 23 mm respectively. Cranial and caudal extent of CTV delineation with respect to IPS was at 48 mm and 50 mm respectively (Table 1) . On prospective clinical validation, after a median follow up of 24 months (IQR = 5-31), 11 out of 14 patients are alive without disease. Two patients died due to disease out of which 1 patient developed regional in-field recurrence. None of the patients developed marginal recurrences. None of the patients developed CTCAE grade III lymphedema or RTOG ≥ grade II skin toxicity.

Figure 1

Table 1

Conclusion This study analyzed pattern of distribution of inguinal nodes and proposes guidelines for inguinal CTV delineation in penile cancer. The proposed guidelines were validated prospectively in a cohort of patients and found to be implementable and safe. PD-0853 Experience of penile brachytherapy in Zambia – building a case for HDR in constrained environments D. Lombe 1 , B. M'ule 2 , K. Mwala 3 , M. Phiri 1 1 Cancer Diseases Hospital, Oncology, Lusaka, Zambia; 2 Cancer Diseases Hospital, Medical Physics, Lusaka, Zambia; 3 Cancer Diseases Hospital, Surgical Oncology, Lusaka, Zambia Purpose or Objective In Zambia, penile cancer is the 10 th most common in men with an incidence rate of 3/100 000. High dose rate brachytherapy is an established modality of treatment for T1-3 (AJCC 2017) lesions. We present our experience of establishing a high dose rate (HDR) interstitial penile brachytherapy service in a high volume resource-constrained environment. Materials and Methods Over a period of 6 months 5 penile cancer patients, T3N1-2M0 lesions (AJCC 2017), were treated with interstitial HDR. The implants where done under spinal anesthesia or a penile block. Flexible catheters were placed using stainless steel needles with trocar. Three patients had catheters inserted free hand and 2 with a breast template. Planning CT scan was done with 1 mm slice thickness. A prescription dose of 38.4 Gy in 12 fractions at 3.2 Gy twice daily was delivered in split plans to accommodate the 6 channel machine when the catheters were more than 6. All the patients underwent inguinal lymph node dissection and adjuvant