# Radiation Oncology/Testis/Overview

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Testes Overview

## Epidemiology

* 7000 cases/yr.
* Most common neoplasm in men ages 15-35.
* Highest incidence among white males especially from northern Europe.
* ~2/3 are clinical Stage I
* Most common testicular cancer in men >50 is lymphoma
* GCTs sometimes present in extragonadal sites: mediastinum, brain and sacrococcygeal region (often midline)

## Anatomy

* Surrounded by tunica albuginea
* Seminiferous tubules lead to rete testis, epididymis, vas efferens and finally to urethra
* Seminiferous tubules
** Spermatogonia participate in sperm production (~67 days)
** Sertoli cells are epithelial cells lining seminiferous tubules
*** Nurture and support the developing sperm cells through the stages of spermatogenesis
*** Produce several hormones, including estradiol to regulate spermatogenesis and androgen-binding protein to transport androgens
*** Form blood-testis barrier
** Leydig cells are interstitial cells
*** Responsible for endocrine function, primarily via production of testosterone
*** Controlled by LH (testosterone synthesis) and FSH (increase in number of LH receptors)
* Rete testis = anastamosing network of tubules in the testicular hilum; sperm are concentrated
* Epididymis = sperm maturation and storage

## Natural history

10% of germ cell tumors may arise in non-gonadal sites, in which case it is usually an anterior mediastinal mass (as opposed to a posterior mediastinal mass, which is usually metastatic) or centrally located retroperitoneal (as opposed to lateralized masses seen in metastatic disease)

## Risk Factors

* Testicular abnormalities
** Cryptorchism
** Testicular atrophy
** Infertility
* Genetic abnormalities
** cKIT mutation is associated with bilateral testicular germ cell tumors

## Pathology

95% are germ cell tumors (Percentages taken from)
* Germ cell:
** Seminoma (50%)
** Non-seminoma (50%)
*** Pure (15%): Embryonal (10%), teratoma (3-5%), choriocarcinoma (<1%), yolk-sac tumor (<1%)
*** Mixed (35%)
* Sex-cord stroma:
** Leydig cell, Sertoli cell, granulosa cell
* Lymphoma:
** Common in men > 50
If the tumor has any component of a non-seminoma, it should be classified as a non-seminoma. If there is an elevated AFP even if the histology shows a pure seminoma, it should be classified as a non-seminoma.
* Seminoma - no differentiation; retains some aspects of spermatogenesis
* NSGCT - undergo some differentiation to totipotential cells
** Embryonic tissue differentiation - embryonal carcinoma and teratoma
** Extra-embryonic tissue differentiation - choriocarcinoma and yolk sac tumors
* Teratoma is not sensitive to chemotherapy. Requires resection. Does not metastasize.
* Choriocarcinoma is one of few tumors that metastasize more frequently hematogenously (also follicular carcinoma of the thyroid, renal cell carcinoma)

## Tumor markers

Check AFP, B-HCG, and LDH.
* AFP - yolk sac, embryonal. Half-life is 5-7 days.
** Elevated in 70% of patients with teratocarcinomas and embryonal carcinomas.
** Never elevated in Seminomas
* B-HCG - choriocarcinoma, embryonal. Half-life is 18-36 hrs.
** Elevated in 40-60% of nonseminomas and ~10% of seminomas
* Placental Alk Phos - most sensitive for surveillance of pure seminomas with ~50% sensitivity for metastatic disease
* LDH - Surveillance marker with slight rise in ~80% of advanced seminomas and 60% of nonseminomas
1 in 5 pts with pure seminoma will have minimal B-HCG elevation (<100 mIU/mL). Tumor markers not elevated in pure teratomas.

## Prognostic factors

Risk stratification:
* Tumors can be classified as good risk, intermediate risk, or poor risk using the IGCCCG system.
* For details see at Seminoma or Non-seminoma

## Radiation technique

* Para-aortic field borders - Designed to cover the potential drainage areas of the para-aortic region, remember testicular vein returns at L2.
** Top border - At or near the crura of the diaphram to cover insertions of the renal vein and antegrade flow
** Inferior border - Bifurcation of the common iliacs
** Lateral borders- Transverse processes of the vertebral bodies to cover LNs. Keep in mind L renal hilum.

## Toxicity

* For risk of second malignancies, please see the second malignancies page

## Review

* Erasmus, 2006 (Netherlands) PMID 17158533 -- "Controversies in the management of clinical stage I testis cancer." (de Wit R, J Clin Oncol. 2006 Dec 10;24(35):5482-92.)

## References

* ↑ Ulbright TM, Amin MB, Young RH. Tumors of the testis, adnexa, spermatic cord, and scrotum. Atlas of tumor pathology. 3rd series. Fascicle 25. Washington, DC: Armed Forces Institute of Pathology, 1999.